Column 1 | Author, year, country (Reference) | (self-explaining) | |
Column 2 | Study type | The following types are differentiated: cross-over, cross-sectional, RCT (randomized controlled trials), longitudinal, case-control, prospective | |
Column 3 | User groups/Duration of product use | If available number (N) in each group, duration and daily consumption of product use, mean age of group is provided. If not indicated other, groups contain both sexes. Important study design features are also provided. | |
Column 4 | Endpoints and findings | Major endpoints are given in bold. Abbreviations, see corresponding section at the beginning of the review. | |
Column 5 | Comments (bias, compliance, etc.) | The authors’ main conclusion is provided (labeled as such, AO). Comments on issues with product compliance (in particular exclusive use of an NGP over a longer time period), generally originate from the review authors (ARO). | |
Column 6 | Conclusions of nicotine’s role | Statement from the study authors (indicated as such, AO) or review authors are provided (ARO). In red, a simplified code for nicotine (N)’s role in generating the reported effects is stated: | |
? | |||
0 | |||
0.5 | |||
1.0 | |||
Combinations of codes are possible. | |||
Column 7 | Limitations (L) / Gaps (G) / Proposals (P) | These evaluations in general originate from the review authors (AOR). Proposals are provided, if the endpoints of the study look promising and an improved study is assumed to provide valuable data. |
Author, year, country (Ref) | Study type | User groups / duration of product use | Endpoints and findings | Comments (bias, compliance, etc.) | Conclusions regarding nicotine's ( |
Limitations (L) / Gaps (G) / Proposals (P) |
---|---|---|---|---|---|---|
J |
Cross-sectional |
94 Males: • 33 Smokers (CC), 41.3 y, CC use since 5.4 y, 13.3 cig/d • 31 Vapers (EC), 37.6 y, EC use since 2.2 y, 6.8 sessions/d • 30 NU, 40.7 y |
Perceived oral symptoms (OS): • • • |
AO: periodontal inflammation and self-perceived OS were poorer among CC than among EC. ARO: Dual users were excluded, but no verification of EC only users. |
The authors cite evidence that ARO: Study data do not allow to deduce |
L: Small groups. G: No verification of EC only use; no N-free EC group. |
? / 0.5 | ||||||
B |
Cross-sectional |
• 45 Former smokers (FCC), mean 47 y • 45 EC users (EC), mean age 47 y, ECs for at least 6 months, |
• • • Not sign. diff.: • • • • • • • Total |
AO: EC use is linked to three types of inflammatory lesions, but not in precancerous lesions. ARO: Only self-reports, no objective check for dual use. |
ARO: |
L: Small group sizes, only medium- to short-term use of EC. G: No check for dual use; no N-free EC group. P: Larger long-term study with EC only use verification and an N-free EC group would be of interest. |
? | ||||||
M |
Cross-sectional |
154 Males: • 39 Smokers (CC), 42.4 y, duration of habit: 17.2 y, 16.2 cig/d, 4.8 min/cig • 40 Waterpipe (WP), 44.7 y, duration of habit: 14.6 y, 4.3 WP/d, 17.1 min/WP • 37 Vapers (EC), 28.3 y, duration of habit: 3.1 y, 9.2 cig/d, 8.1 min/cig • 38 NU, 40.6 y |
Oral health parameters, > / <: sign. diff.: • PI: CC ≈ WP > EC* ≈ NU * not sign. diff. from all other groups • BoP: CC ≈ WP > EC ≈ NU • PD: CC ≈ WP > EC ≈ NU • CAL: CC ≈ WP > EC ≈ NU • MBL: CC ≈ WP > EC ≈ NU BMs in saliva: • Cot: CC ≈ WP ≈ EC > NU • IL-1ß: CC ≈ WP > EC ≈ NU • IL-6: CC ≈ WP > EC ≈ NU |
AO: Parameters of oral health were poorer in CC and WP than EC and NU. ARO: Dual users were excluded, but no verification of EC only use. EC group is significantly (?) younger! |
Authors cite constricting effect of ARO: |
L: Small group sizes; EC only use not objectively verified. G: No inclusion of an N-free EC group. |
? | ||||||
A |
Cross-sectional |
Male subjects with teeth implant : • 40 Smokers (CC), 45.8 y, CC since 21.3 y • 40 Water pipe users (WP), 43.5 y, WP use for 19.5 y • 40 Vapers (EC), 35.6 y, EC use for 8.7 y, 6.5 sessions/d, 37.7 min/session • 40 Non-smokers (NS), 42.6 y |
• PI: Sign. higher in CC, WP, EC • • • Sign, higher in CC, WP, EC • Sign. higher in CC, WP, EC than in NS |
ARO: The authors do not interpret their results with EC users. No information on possible dual use of EC and other products. |
The authors state that ARO: A role of |
G: No N-free EC group; no information on possible dual use EC/other products (CC, WP). P: A study with these gaps filled would be of interest. |
0.5 / ? | ||||||
A |
Cross-sectional |
Subjects with teeth implants: • 47 Male vapers (EC), 35.8 y, mean EC use: 4.4 y, 6.5 sessions/d, 37.7 min/session • 45 Male never smokers (NS), 42.6 y |
Peri-implant parameters: • • • PD: sign. higher in EC than NS • TNF-α and IL-1ß in PISF: sign. higher in EC than NS |
ARO: No information on possible additional CC use. |
The authors state that ARO: A role of |
G: No N-free EC group; no CC group (positive control); no information on possible dual use EC/CC. P: A study with these gaps filled would be of interest. |
0.5 / ? | ||||||
A |
Longitudinal |
• 9,632 Never EC users (nEC) • 329 Longitudinal EC users (LEC) for at least 1 year • 8,298 Occasional EC users (OEC) PATH study, waves 1, 2, 3 |
LEC sign. increased compared to nEC at wave 3 for: • • • any nEC and OEC were not sign. different |
AO: EC use may be harmful to oral health. ARO: All data on behavior and endpoints were self-reports. |
ARO: |
L: Only self-reports; EC use might be too short. G: No objective verification of EC only use; no N-free EC group. |
? | ||||||
B |
Cross-sectional |
• 46 CC users (14.2 pack × years) • 44 EC users (duration of use: 9.4 y) • 45 NU (never used CC or EC) |
Periodontal health status: CC < EC < NU Indicators: PI, BOP, |
AO: Periodontal status is poorer and GCF levels of proinflam. cytokines are higher in CC compared with EC and NU. There is evidence for increased periodontal inflammation in EC users. ARO: Compliance of EC use not approved (could be questionable). |
ARO: |
L: Small group sizes; EC compliance questionable (given the long duration of use). |
? | ||||||
A |
Cross-sectional |
102 Males with tooth implants: • 35 Smokers, 36.3 y, daily CC use for > 12 months • 33 Waterpipe (WP) users, 34.1 y, daily WP use for > 12 months • 34 Vapers, 33.5 y, daily EC use for > 12 months, 8.4 mg N/mL • 35 NU, 32.2 y |
• |
AO: Cotinine peri-implant in fluid was increased in users of ARO: Dual users were excluded, but not verification. |
Authors suggest that ARO: |
L: Small group sizes, unclear compliance (particularly of EC group). G: No N-free EC group, no objective verification of compliance. |
? / 1.0 | ||||||
A |
Cross-sectional |
95 Males with tooth implants: • 32 Smokers (CC), 40.4 y, CC since 13.7 y, 11.3 cig/d • 41 Vapers (EC), 35.8 y, EC since 4.4 y, 6.5 sessions/d, 37.7 min/session |
Peri-implant sign diff: • • • • • • |
AO: Peri-implant is compromised by CC and (to smaller degree) also by EC. ARO: Dual users were excluded, but not verification of status. |
The authors point out that ARO: |
L: Small group sizes; unclear compliance. G: No N-free EC group; no objective verification of EC only use. |
0.5 / ? | ||||||
A |
Longitudinal |
89 Males, at least 30% BOP: • 28 Vapers (EC use daily since at least 12 months, no history of tobacco use), 32.5 y • 30 Smokers (CC, > 5 cig/d on the previous 12 months), 36.4 y • 31 NU, 32.6 y Investigations at BL, 3 and 6 months; FMUS after BL |
|
AO: State to be cautious with the interpretation of the results due to weaknesses in the study design. ARO: Dual users excluded, but no verification of EC only use. |
ARO: |
L: Low number of subjects, short duration of product use. G: No N-free EC group, no verification of EC only use. |
0.5 / ? | ||||||
T |
Cross-sectional |
• 42 EC users, 28 y, CotP: 115 ng/mL • 24 CC users, 42 y, CotP: 122 ng/mL • 27 NU, 24 y, CotP: 2.5 ng/mL |
|
AO: The findings have significant impact on public health. ARO: Possible dual use not considered. |
ARO: cannot be deduced from the study results. |
L: Small group sizes; dual use is possible. G: No N-free group. P: Study with the weaknesses eliminated would be of interest. |
? | ||||||
A |
Cross-sectional |
71 Subjects with chronic periodontitis: • 36 Vapers (EC), 47.7 y, mean duration of EC: 3.3 y, 17.6 sessions/d, 8.4 puffs/session, all were former smokers • 35 NU, 46.5 y Investigations at BL and 3 months, in between: SRP |
BL: no sign. diff. between EC and NU in |
AO: The anti-inflammatory effect of SRP was higher in NU than in EC. ARO: No verification of EC only use. |
ARO: |
L: Small group sizes. G: No verification of EC only use; no N-free EC group. |
? | ||||||
K |
Cross-sectional |
Periodontitis patients: • 19 Smokers (CC), 35.3 y, smoking for 14.0 y • 19 Vapers (EC), 34.7 y, CC use for 12.1 y than switched to EC since at least 12 months • 19 Former smokers (FS), 35.6 y, CC use for 12.1 y then stopped since at least 12 months |
• • • BMs in GCF: • • • • |
AO: CCs and ECs had the same unfavourable effects on the markers of oxidative stress and inflammatory cytokines. ARO: Dual smokers (CC and EC) were excluded. No information on compliance. |
ARO: Role of nicotine cannot be deduced from the study. |
L: Small group sizes, no long-term use of ECs, no information on unique EC use in vapers. G: No N-free EC group. |
? | ||||||
Y |
Cross-sectional |
• 12 NU, 35.7 y, CotS: 0.56 ng/mL • 12 CC, 40.3 y, CotS: 142.5 ng/mL • 12 EC, 34.9 y, CotS: 180.2 ng/mL, • 12 Dual (EC, CC) users (DU), 39.4 y, CotS: 299.0 ng/mL |
Sign. diff. between groups: CotS: DU > NU • • GCF • • • Various growth factors: none |
AO: EC/CC induced differential changes on oral health. ARO: Strange sign. diff. for CotS and some other BMs. No detailed assessment of product use. |
ARO: |
L: Small group sizes; EC compliance questionable. G: No N-free EC group. |
? | ||||||
V |
Cross-sectional |
105 Males: • 28 Smokers (CC), 33.3 y, 6.1 pack-years • 26 EC users, 31.6 y, 0.9 y EC use, 30.2 sessions/d • 25 JUUL (JU) users, 32.1 y, 0.8 y JU use, 25.3 sessions/d • NU, 33.5 y |
Self-rated • • • • Periodontal parameters, sign. diff.: • • • • |
AO: Pain in teeth and gums are more often perceived by CC than EC and JUUL users and NU. ARO: Dual users were excluded, but no verification of EC or JUUL only use. |
Authors cite evidence that ARO: Study results do not provide evidence for N's role in oral health. |
L: Small group sizes; only short use of EC and JU. G: No N-free EC group. |
? | ||||||
I |
Cross-sectional |
Male subject • 30 Smokers (CC), CC habit: 18.3 y, 12.6 cig/d, 8.3 min/cig • 30 WP users, WP habit: 15.6 y, 5.5 WP/d, 22.6 min/WP • 30 EC users, EC habit: 6.4 y, 15.4 sessions/d, 20.5 min/session • 30 NU |
Oral health, sign. diff. (</>): • • Markers in GCF: • • |
AO: All product users (including EC) show impairment of oral health. ARO: Dual users were excluded. No verification of possible dual use in subgroups. |
The authors cite some evidence that ARO: From this study, no involvement of |
L: Small group sizes; unclear, whether only EC were used (no objective verification). G: No N-free EC group. P: A larger study without these weaknesses would be worthwhile. |
? / 0.5 | ||||||
P |
Cross-sectional |
• 39 NU, (m/f): 29/38 y, COex: 1.8 ppm, CotS: 11.9 ng/mL • 40 EC users, (m/f): 36/36 y, COex: 5.1 ppm, CotS: 104 ng/mL • 40 CC users, (m/f): 46/45 y, COex: 18.8 ppm, CotS: 536 ng/mL |
Sign. diff. in EC from NU and also from CC |
AO: EC users are more prone to infections. ARO: Dual use not unlikely (see COex in EC). |
The authors mention evidence that ARO: |
L: Small group sizes; long-term product use not well characterized, misclassification possible. G: No N-free EC group. |
? | ||||||
F |
Cross-sectional |
64 Subjects, 28–83 y: • 15 Controls (NU) • 18 CC users • 16 Mixed (CC, EC) • 15 EC users |
• • *: sign. diff. in ANOVA EC closer to CC and mixed than to NU. |
AO: The combined findings of this study and previous studies put into question the safety of ECs as a smoking cessation mechanism. ARO: No statement on duration of EC use, no check of self-reported product use. |
ARO: |
L: Small group sizes. G: No information on duration of use of products. |
? | ||||||
A |
Longitudinal |
• 30 Male vapers (EC), ≥ 2 y EC use • 30 Male smokers (CC), ≥ 2 y CC use • Investigations at BL, 3 and 6 months |
Sign. differences • • Sign. dose-response in CC group (pack-years) for: • PD, Sign. dose-response in EC group (session-years) for: • PD (all time points), MMP-8 (3 and 6 months) Effects higher in CC than EC. |
AO: CC showed higher periodontal worsening than EC. MMP-8, CTX are prognostic factors for clinical attachment loss in CC and EC users. ARO: No verification of pure EC or CC status. |
ARO: |
L: Small groups, 6 months might be too short. G: No N-free group. P: Larger study with verified long-term users would be of interest. |
? / 0.5 | ||||||
T |
Longitudinal |
• 27 CC users, (m/f): 48/51 y • 28 EC users, (m/f): 36/40 y • 29 NU, (m/f): 29/39 y Investigations at BL and 6 months later |
• consistent for 3 groups over time • Unique in EC group, higher agreement with CC • No clear group diff. for • |
AO: Suggest that there is a unique periodontal risk associated with e-cig use (similar to CC). ARO: EC only use not verified. |
The authors assume that ARO: |
L: Small group sizes; duration of EC use too short? G: No N-free EC group. |
? | ||||||
C |
Longitudinal (6 months) |
• 20 NU • 20 EC users • 8 CC users |
CC / EC / NU: 446 /179 / 21.0 |
AO: This is the first identification of a carcinogen-DNA adduct in any tissue of EC users. |
ARO: No involvement of |
L: Small group sizes; dual use cannot be completely excluded. P: Larger study with a long-term verification marker would be of interest. |
0 | ||||||
M |
Cross-sectional |
76 Subjects, ~25 y : • 12 Snus (including • 19 Smokers (CC) • 8 Vapers (EC) • 37 NU |
• Only seen in snus group • • • • |
AO: Saliva is a suitable matrix for detecting oral mucosa changes. Product use relies on self-reports. |
ARO: |
L: Small groups; not well characterized product use history; snus and G: No N-free EC group. |
? | ||||||
T |
Cross-sectional |
72 Healthy, young subjects: • 24 EC only users, 24.3 y, CotP: 84.9 ng/mL • 24 CC only users, 26.0 y, CotP: 76.7 ng/mL • 24 NU (no CC, no EC), 25.3 y, CotP: 2.6 ng/mL |
• • EC: dose-dependent and device-dependent |
AO: DNA damage was shown for the first time. ARO: EC/CC use only short-term verified. |
The authors state that N-content in e-liquid was not a predictor for DNA damage. ARO: No role of |
L: Product use not verified (long-term); small group sizes; DNA lesions are unspecific (strand breaks, bulky adducts, oxidation, etc.). P: A larger study, avoiding the weaknesses with a specific DNA analysis would be of interest. |
0 / ? |
Chronic obstructive pulmonary disease (COPD) | A preventable and treatable disease characterized by airflow limitation that is not fully reversible. The limitation is usually progressive and is associated with an abnormal inflammatory response of the lungs to noxious particles or gases, primarily caused by cigarette smoking. Although COPD affects the lungs, it also produces significant systemic consequences. |
Emphysema | Permanent enlargement of the airspaces distal to the terminal bronchioles, accompanied by destruction of their walls and without obvious fibrosis. In patients with COPD, either condition may be present. However, the relative contribution of each to the disease process is often difficult to discern. |
Asthma | A chronic inflammatory disease of the airways in which many cell types play a role — in particular, mast cells, eosinophils, and T lymphocytes. In susceptible persons, the inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness, and cough, particularly at night and/or in the early morning. These symptoms are usually associated with widespread and variable airflow obstruction that is at least partly reversible either spontaneously or with treatment. The inflammation also causes an associated increase in airway responsiveness to a variety of stimuli. |
Author, year, country (Ref) | Study type | User groups / duration of product use | Endpoints and findings | Comments (bias, compliance, etc.) | Conclusions regarding nicotine's ( |
Limitations (L) / Gaps (G) / Proposals (P) |
---|---|---|---|---|---|---|
H |
Case-control |
35–64 y old men: • 585 Cases with MI • 589 Controls Duration of SLT use: 10–30 y |
ORs (CI) • CC: 1.87 (1.40–2.48) • SLT: 0.89 (0.62–1.29) |
AO: Snuff dipping for middle aged men is associated with a lower risk for MI than smoking (CC). ARO: No verification of SLT use. |
The authors suggest that CO and PAH, rather than |
L: Relative low number of cases/controls using SLT (10–15%). G: Dual use (SLT+CC) not assessed. P: Larger study which avoids these weaknesses would be of interest. |
0 / ? | ||||||
H |
Case-control |
WHO MONICA study, 25–64 y old men: • 687 MI cases • 687 Controls Duration of SLT use: 5–30 y |
ORs (CI) for first • SLT only (N=59): 0.96 (0.65–1.41) • CC only (N=248): 3.65 (2.67–4.99) SLT risk slightly (not sign.) higher for fatal MI (OR=1.50) |
AO: MI is not increased in snuff dippers. ARO: Dual use was evaluated separately, but no verification for SLT only users. |
The authors conclude that |
L: Small group sizes; only men, relatively young population. G: No other NGPs; no N-free ECs. |
0 | ||||||
H |
Prospective | 118,395 healthy, never-smoking men (construction workers), 19 years (mean) of follow-up |
• Non-fatal: 0.91 (0.81–1.02) • Fatal: 1.28 (1.06–1.55) • Fatal, highest consumption: 1.96 (1.08–3.58) |
AO: Snuff use increases the risk of fatal MI. ARO: Tobacco use information was obtained from questionnaires at entry. |
The authors cite evidence that Participation of |
L: RR are very low and only sign. for fatal MIs; no clear dose-response; tobacco habits rely on self-reports; changes in habits are not assessed. |
0.5 / ? | ||||||
B |
Case-control and Prospective (meta-analysis) |
9 Epi studies on MI 6 Epi studies on stroke in Sweden (Swe) and USA Duration of use: 20 y (estimate) |
RR (CI) of current SLT users (number of studies): Any • Swe (6): 0.87 (0.75–1.02) • USA (3): 1.11 (1.04–1.19) Fatal MI: • Swe (5): 1.27 (1.07–1.52) • USA (3): 1.11 (1.04–1.19) Any • Swe (3): 1.02 (0.93–1.13) • USA (3): 1.39 (1.22–1.60) • Swe (3): 1.25 (0.91–1.70) • USA (3): 1.39 (1.22–1.60) |
AO: Use of SLT increases the risk of fatal MI and stroke, which does not seem to be explained by chance. ARO: Dual use (SLT + CC) is a general issue. |
The authors cite evidence that ARO: From the data, the role of |
L: Heterogeneity; SLT products in USA and Sweden are different, limited or no dose-response shown. G: No other NGPs. |
0.5 / ? | ||||||
A |
Prospective (2 studies) |
• ULSAM: 1,056 elderly men, never smoking, median FU 8.9 y • CWC: 118,425 construction workers, never smoking, median FU 18 y Duration of snus use: 50 y (estimate) |
• ULSAM: 2.08 (1.03–4.22) • CWC: 1.28 (1.00–1.64) |
AO: Use of snus increases the risk of heart failure. ARO: Snus only use was not verified. |
The authors assume that ARO: |
L: Low case numbers (particularly in ULSAM study); no reliable information on tobacco use habits (misclassification possible); no dose-response observed; men only. |
0.5 / ? | ||||||
A |
Cross-sectional (NHIS = National Health Interview Survey) |
Survey of 2014 and 2016 • 60,100 NU, 51.9 y, 2,309 MIs • 7,093 Former EC users, 39.9 y, 225 MIs • 1,483 EC some days, 41.4 y, 61 MIs • 776 EC daily (41 never smoked), 44.2 y, 47 MIs Duration of EC use: < 10 y (?) |
Adjusted ORs (CI) for • Former EC: 1.06 (0.86–1.30) • EC some days: 1.16 (0.83–1.62) • EC daily: 1.79 (1.20–2.16) |
AO: Daily use of EC increases the MI risk. ARO: Dual use was adjusted in the ORs, no verification. |
ARO: |
L: All data rely on self-reports. G: No N-free EC group. Causality between EC use and MI was questioned in a letter to the editor (47). |
? | ||||||
V |
Cross-sectional |
National Health Interview Survey, 2014, 2016, 2017, 2018; 16,855 participants: • 2,848 NU, 30.3 y • 401 Vapers (EC), 26.7 y • 7,291 Tobacco users (mostly CC), 44.0 y • 2,240 Dual, 42.2 y Duration of EC use: < 10 y (estimate) |
Adjusted ORs (CI) • EC: 4.09 (1.29–12.98) • CC: 4.52 (2.49–8.21) • Dual: 5.44 (2.90–10.22) • EC: 1.22 (0.36–4.18) • CC: 2.15 (1.38–3.35) • Dual: 2.32 (1.44–3.74) • EC: 0.67 (0.18–2.44) • CC: 1.90 (1.20–3.11) • Dual: 2.27 (1.37–3.77) |
AO: EC users have an increased risk for MI. The highest risk for MI, stroke and CHD were observed for dual users. ARO: Grouping relies on self-reports (danger of misclassification). |
ARO: |
L: All data rely on self-reports (misclassification of product use is possible). G: No N-free EC group. |
? | ||||||
H |
Prospective |
118,395 healthy, never-smoking men (construction workers), enrolled 1978–1993, follow-up 2003 • 3,248 cases of stroke Duration of snuff use: 10–30 y (estimate) |
RR for ever snuff users: • All • • Fatal |
AO: Snuff use increases the risk of fatal ischemic stroke. ARO: Tobacco use information was obtained from questionnaires at entry. |
The authors cite evidence that ARO: Participation of |
L: RR are very low and only sign. for fatal ischemic strokes; no clear dose-response; tobacco habits rely on self-reports; changes in habits are not assessed. |
0.5 / ? | ||||||
P |
Cross-sectional |
Telephone survey, 161,529 young adults (18–44 y): • 13,3077 NU • 13,318 CC only • 3,437 EC only • 4,204 EC/exCC • 7,493 Dual Duration of EC use: < 10 y (estimate) |
OR (CI) for • CC only: 1.59 (1.14–2.22) • EC only: 0.69 (0.34–1.42) • EC/exCC): 2.54 (1.16–5.56) • Dual: 2.91 (1.62–5.25) |
AO: Sole EC use is not a risk factor for stroke. ARO: All data rely on self-reports (no verification of product use). |
The authors cite evidence that ARO: Absence of risk in EC only would suggest no role of |
L: Misclassification due to self-report is possible; switching to EC due to early symptoms possible. G: No N-free EC group. |
0 / ? | ||||||
B |
Cross-sectional |
Behavior and risk factor survey (BRFSS), 2016, 486,303 participants: • G1: EC every day, m/f: 2,778/2,229 • G2: EC some day, m/f: 5,018/5,151 • G3: Former EC, m/f: 29,014/29,815 • G4: NU, m/f:164,605/226,937, older than G1–G3 Duration of EC use: < 10 y (estimate) |
Adjusted OR (CI) for • G1: 1.62 (1.18–2.31) • G2: 1.28 (1.02–1.61) • G3: 1.09 (0.98–1.23) |
AO: EC use is of potential concern for CVD. Self-reports and cross-sectional design can lead to confounding and bias. |
ARO: |
L: Only short use of EC (2007–2016); most participants were former CC users; dual use possible; temporality (due to cross-sectional design) not determined. |
? | ||||||
Z |
6 Cross-sectional studies (meta-analysis) |
1,134,896 Subjects, groups used for meta-analysis: • EC1: EC users (all, including only, dual, former CC) • EC2: EC only users • EC3: Current dual users • EC4: EC only users, former CC users • CC: CC only users • NU: no EC, no CC Duration of EC use: ? |
OR for prevalence of • EC1 • EC2 • EC3 • EC4 Subgroup analysis had lower heterogeneity |
AO: The role of EC use in stroke development is inconclusive due to the strong effect of former CC use. ARO: General problems with misreports of product use. |
L: Partly low quality studies; stroke types not differentiated; misclassification of product use possible; temporality unclear in cross-sectional studies. G: No prospective studies available; no N-free EC groups available. |
|
? | ||||||
P |
Cross-sectional |
NHANES 2015–2018, 79,825 users: • 7,756 EC users, 48y • - EC1: EC use in last 30d • - EC2: No EC use in last 30d • 23,444 Dual users, 50y • 48,625 CC users, 59y EC users are sign. younger |
Adjusted ORs (CI) for • EC • Dual • EC1 * discrepant to the text!? |
AO: Stroke in EC users was earlier in onset than in smokers. ARO: Usual problems with cross-sectional approach (temporality, recall bias). |
The authors cited evidence that |
L: Temporality in cross-sectional studies; misreports in product use; stroke not further classified. G: No N-free EC group. |
0.5 | ||||||
W |
Cross-sectional |
577 young men (18–19 y): • 377 NU • 43 CC only • 127 Snuff only • 30 Dual (Snuff + CC) |
Sign. diff. in CVD-related BMs in urine: • Tx-M: CC > NU, Dual > NU |
AO: CC but not snuff use facilitates TBX-A2 formation, reflecting platelet activation and potential CVD development. ARO: No verification of snuff only use. |
The authors cite evidence that ARO: |
L: Small user group sizes; young men only. G: No other NGPs (EC, HTP), N-free EC. P: Larger study with older subjects, including additional NGPs would be of interest. |
? | ||||||
B |
Prospective |
Male construction workers, up to 65 y (1970/71), follow-up after 12 years for mortalities: • 32,546 NU • 6,297 SLT users • 14,983 Smokers (CC1), < 15 cig/d • 13,518 Smokers (CC2), ≥ 15 cig/d Duration of SLT use: 10–40 y (estimate) |
RR (CI) compared to NU: • – SLT: 1.4 (1.2–1.6) – CC1: 1.8 (1.6–2.0) – CC2: 1.9 (1.7–2.2) • – SLT: 1.1 (0.9–1.4) – CC1: 1.5 (1.3–1.8) – CC2: 2.5 (2.2–2.0) • – SLT: 1.4 (1.3–1.8) – CC1: 1.7 (1.6–1.9) – CC2: 2.2 (2.0–2.4) |
AO: Both CC and SLT users have an increased risk for CVD, risk for SLT is lower. ARO: SLT (only) use was not verified, dual use is not unlikely. |
The authors cite evidence that ARO: |
L: Only male workers (healthy-worker effect?); dual use (SLT+CC) is possible. G: Other NGPs; ECs without |
0–0.5 | ||||||
B |
Cross-sectional |
143 Men, 35–60 y: • 40 NU, 43.1 y, CotP: 3.8 ng/mL • 28 SLT users, 44.4y, median 25y of SLT use, CotP: 338 ng/mL • 29 Smokers (CC), 48.0y, median 30y of CC use, CotP: 248 mg/mL |
Markers for • • • • • • • • • Alcohol consumption: ↑ |
AO: The increased occurrence of atherosclerosis in smokers is caused by other components of tobacco smoke than nicotine. ARO: SLT only use not verified. |
The authors state that, while |
L: Small group sizes; SLT group might contain dual users. G: No other NGPs included. P: A study avoiding these weaknesses would be worthwhile. |
0 | ||||||
W |
Cross-sectional |
391 Healthy men, 58 y • 139 NU (never SLT, never CC) • 48 SLT users (29% also smoked) • 96 CC users |
Risk factors for • SLT: • CC: |
AO: Smoking, but not SLT is an import risk for atherosclerosis. ARO: No exclusive SLT group evaluated. |
The authors conclude that the data clearly indicate that |
L: Only men, only one age. G: No exclusive SLT group, no other NGPs. |
0 | ||||||
Y |
Prospective (1987/89, FU: median 16.7 y later) |
• NU (no SLT, no CC): Total: 9,906; 1,510 CVD cases • SLT (no CC): Total: 354; 102 CVD cases; SLT = Snuff + chewing tobacco |
Harm ratio (CI) for • SLT: 1.31 (1.06–1.61) • CC (only): lower CVD risk than SLT!? |
AO: SLT use increases the risk CVD and is no alternative to CC use. ARO: SLT use only was not verified. |
No statement on role of ARO: A role of |
L: Misclassification of SLT (and CC) is possible (also conceded by the authors). |
? | ||||||
N |
Cross-over |
40 Subjects (20 S and 20 NS) were investigated under 2 conditions, separated by 1 week: • C1: Vaping, 9 puffs, EC with 16 mg N/mL • C2: Smoking, 1 CC (0.6 mg N/cig); Blood samples for BM analysis were taken right before and 5 min after product use |
Sign. diff. between S and NS at baseline: • sCD40L: higher in S • sP-Selectin: higher in S Changes pre/post: Elevation in NS and S under both conditions (C1, C2) for the 3 BMs • • • |
AO: Both CC and EC use acutely increase platelet activation. |
ARO: Involvement of |
L: Low number of subjects. G: No ECs without P: Results suggest a chronic effect of smoking on sCD40L, sP-Selectin. Therefore a larger study with long-term (> 12 months) use of CC and EC would be worthwhile. |
? | ||||||
M |
Cross-over |
17 occasional smokers were assigned to 2 conditions, separated by 1 week: • C1: EC with • C2: EC without BM measurements at 0, 2, 4, 6 h post vaping |
C1: sign. increase in: • • • • C2: sign. increase only in • BM4 (smaller than in C1) |
AO: As few as 30 puffs of nicotine-containing EC vapor caused an increase in levels of circulating E |
ARO: Nicotine likely to be involved in the acute increase of all 4 BMs. |
L: Low number of subjects. G: BM levels after chronic use of EC and other NGP use. |
1 | ||||||
S |
Cross-sectional |
Young adults: • 20 Smokers (CC), 27.0 y • 20 EC users (EC use only for the past 3 months, 80 % were previous smokers), 25.7 y, • 20 NS, 24.6 y |
|
AO: CC and EC users had significantly more carotid plaque burden compared to NU. Results further indicate that vaping does not cause an increase in vascular inflammation. ARO: Product use was self-reported (no biochemical validation). |
ARO: Role of |
L: Small sample sizes; EC use probably too short and compliance not approved. G: No N-free EC group. |
? | ||||||
G |
Cross-sectional |
17 Men, 18–75 y • 7 NU, 25.6 y, ≥2 containers SLT/week, CotP: < 10 ng/mL • 5 SLT users, 28.2 y, CotP: 226 ng/mL • 5 CC users, 21.2 y, ≥10 cig/d, CotP: 170 ng/mL |
Sign. differences (>/<): • • FMD (nitroglycerine-dependent): NU ≈ SLT ≈ CC |
AO: Endothelial function is sign. impaired by CC and SLT. ARO: SLT only use not verified. |
The authors cite evidence (including their results) that |
L: Small sample size; only men; low average age (short product use period); dual use possible. G: No other NGPs, no N-free EC group. |
1 / ? | ||||||
R |
Cross-over |
20 Snus users (m/f=18/2), mean age: 34 y: • All 20 performed a session with 1 g snus • 10 performed a similar session with placebo Measurements at 0 (BL), 20 and 35 min |
Sign. changes: • • • • |
AO: Oral moist snuff significantly impaired FMD of the brachial artery, predicting an increased CVD risk. |
The authors cite evidence that |
L: Small group size; mostly men, relatively young, only acute effects detected. G: No other NGPs, no N-free EC group. P: A study on chronic FMD impairment would be of interest. |
1 | ||||||
S |
Cross-sectional |
1,592 Healthy men (from HUNT3 Study): • 886 NU, 47.4 y • 238 Snuff only users, 42.8 y • 447 Smokers (CC), 47.4 y • 21 Dual users, 44.0 y |
The diff. in FMD was larger in SLT users with low fitness. Sign. changes: • • • • |
The authors conclude that snus acutely impairs FMD and is a risk factor for CVD. |
AO: The possible role of ARO: Role of |
L: Partly small group sizes; only men; duration of SLT use not provided. |
? | ||||||
F |
Cross-over |
15 Smokers, 22.9 y, were randomly allocated to 3 conditions: • EC(+) with • EC(−) without • CC: 1 CC 48 h washout period between conditions; measurements before and every 15 min after vaping/smoking up to 2 h |
Sign. changes in CC and EC(+) conditions between 15 and 60 min: No change in EC(−) |
AO: Speculate that long-term EC(+) use may increase the risk for CVD. |
ARO: The results suggest the CV effects were caused by |
L: Very small number of subjects; changes after only one use of product was investigated. G: Data allow no deduction of a dose-response relationship for P: A study with long-term EC users avoiding the weaknesses would be of interest. |
1 | ||||||
I |
Cross-over |
70 Smokers (CC) in cessation clinic: Acute study: • G1: 35 vaped ECs with • G2: 35 vaped ECs without Chronic study (1 month): • G3: 24 were dual users (CC/EC) • G4: 42 only used EC • G5: 20 only used CC (control) |
Acute study: • • • Chronic study: • PWV, AIX75, MDA: decrease in G3 and G4 (larger in G4), unchanged in G5 |
AO: The findings suggest that ECs may be used in a medically supervised smoking-cessation program. |
AO: EC use can reduce effect of smoking on arterial stiffness and oxidative stress (acute and chronic). ARO: Effect of |
L: Small group sizes, short duration. P: Perform larger and longer studies. |
0.5 | ||||||
C |
Cross-over |
25 Occasional smokers, 24 y, were allocated to 3 conditions: • Vaping (EC) without • Vaping (EC) with • Sham vaping (EC switched off) Vaping session: 25 puffs (4 s, 30 s intervals). Measurements before (BL) and up to 120 min after vaping |
Changes when vaping with • Impaired • Increased arterial stiffness ( • Increase in • Increase in These parameters did not change upon vaping without |
AO: The observed effects were solely attributable to |
ARO: Measured (acute) effects are caused by |
L: Only acute effects were measured, small group size. P: Similar but larger study with long-term users would be of interest. |
1 | ||||||
G |
RCT |
• G1: 40 CC (> 2 years) • G2: 37 CC switched to EC with • G3: 37 CC switched to EC without |
• • • • • • |
AO: Improvements in women higher than in men. ARO: More compliant groups G2 and G3 (COex < 6 ppm) show higher effect of switching to EC. |
ARO: No evidence that nicotine is measurably involved in the observed effects. |
L: Too short use of ECs; low numbers of subjects in all groups. P: Long-term study (> 12 months) with larger group sizes (> 100/group). |
0 | ||||||
I |
Cross-over | 40 S were switched to EC (12 mg N/mL) for 4 months, |
Sign. changes by condition: • • • • |
AO: Switching to ECs for 4 months has a neutral effect on platelet function while it reduces arterial stiffness and oxidative stress compared to CC smoking. |
ARO: Role of |
L: Small sample size, 4 month probably too short to assess long-term effects. G: N-free EC would be of interest. P: Perform study which overcomes the deficiencies (L, G). |
? | ||||||
C |
Cross-over |
16 NU (no nicotine products in the last 6 months) were assigned to 3 vaping conditions: • V1: 18 puffs, 5.4 % nicotine • V2: 18 puffs, no nicotine • V3: 18 sham puffs Measurements 0, 1 and 2 h after vaping |
Biomarkers: |
AO: Vaping ECs regardless of nicotine content are not significantly different from each other and do not produce lasting effects over the course of a 2-hour trial. |
ARO: No involvement of nicotine can be deduced, since no effects were observed. |
L: Study duration too short (single use of product), too few subjects/conditions. P: Long-term study (> 12 months) with larger group sizes (> 100/group). |
? | ||||||
H |
Cross-over |
• G1:49 Vapers (EC for > 1 year) • G2: 40 Smokers (CC for > 1 year) • G3: 47 NU (non-smokers or ex-smokers for > 1 year) |
• Baseline FMD not sign. diff. between G1, G2 and G3 • Acute CC use of G2: FMD sign. lower (impaired) • Acute EC use of G1 (with/without nicotine, N-inhaler, sham): no sign. diff. • Acute EC use of G3 (NU) (with/without nicotine, N-inhaler, sham): no sign. diff. • Acute use of CC (in G2): sign. increase of all three • Acute use of EC with nicotine, N-inhaler (in G1 and G3: sign. increases • Acute use of EC without nicotine, sham (in G1 and G3: partly decreases, mostly not sign. |
AO: Although it is reassuring that acute EC vaping did not acutely impair FMD, it would be premature and dangerous to conclude that ECs do not lead to atherosclerosis or increase cardiovascular risk. |
ARO: Nicotine is not involved in the acute decrease (impairment) of FMD. |
L: Small group sizes. P: Perform study with larger and well defined (in terms of product use) groups. |
0 | ||||||
Nicotine caused acute increases of HR, SBP and DBP. | ||||||
1 | ||||||
Chronic use of nicotine (with CC or EC) does not lead to permanent changes in FMD, HR, SBP and DBP (at least in the population investigated). | ||||||
0 | ||||||
K |
Cross-over | 20 Smokers vaped 1 EC (18 mg N/mL) with 40 puffs at 30 s intervals over 20 min, measurements for BMs were performed pre and post vaping |
Changes in vapers (pre/post): • • • • |
AO: EC vapour exposure increases vascular, cerebral, and pulmonary oxidative stress via a NOX-2-dependent mechanism. Our study identifies the toxic aldehyde acrolein as a key mediator of the observed adverse vascular consequences. |
Experiments with mice show that: • EC without • acrolein is mostly responsible for the effects of ECs. |
L: (Human study): low subject number, too short. G: (Human study): No condition without |
? (human) / 0 (mice) | ||||||
F |
Cross-sectional |
• 94 NS, 29 y • 285 CC, 32 y • 36 EC, 29 y • 52 Dual, 33 y |
Vascular measures sign. diff. between groups: • Carotid-femoral • Carotid-radial • • • No sign. diff.: • • |
AO: EC use is not associated with a more favorable vascular profile. ARO: No information on EC use duration. |
ARO: |
L: Most groups too small. G: No information on EC use duration; EC without |
0.5 / ? | ||||||
P |
Cross-sectional |
• 51 Smokers (CC), 21.3 y, CC duration 3 y, 3 cig/d • 22 Vapers (EC), 21.4 y, EC duration 4 y (2–6 y), 1 (0.8–1.6)mg N/mL • 197 NU, 21.1 y |
Sign. diff. in BMs: • Albuminuria: EC > CC > NU • – No sign. diff. in |
AO: No association of BMs with ARO: Albuminuria measured with dipstick only. Compliance of EC group not approved. |
ARO: |
L: Only very young subjects; EC use somewhat questionable; albumin method doubtful. G: No N-free EC group. P: Larger study without the weaknesses would be of interest. |
? / 0 | ||||||
C |
Cross-over |
31 NS vaped 1 EC without Blood samples were drawn for BM analysis pre and post vaping |
Sign. changes (post Increases: • • • • • Decreases: • • • |
AO: The findings indicate that a single episode of vaping has adverse impacts on vascular inflammation and function. |
ARO: No statement on the role of |
L: Sample size is low, only acute effects investigated. G: No condition with P: Larger study including ECs with |
? | ||||||
A |
Cross-sectional |
• 24 Snus users (males, healthy), 44.8 y; ≥15 y snus, < 1 y CC use • 26 NU (males, healthy), 43.4 y |
• • Snus users reported sign. higher alcohol consumption at BL. |
AO: Long-term snus use may alter endothelial function and increase CVD risk. |
The authors cite (convincing) evidence that |
L: Snus only use not verified; small group sizes; only males (women could have different CVD risks). P: Larger study with both sexes and product use verification would be of interest. |
1 | ||||||
M |
Meta-analysis (8 studies) |
372 Subjects, conditions compared: • Vaping without • Vaping with • Smoking (CC) |
Endothelial function, acute changes: EC+ • • • EC+ • FMD: no sign. change • PWV: sign. decrease • AI: sign. decrease |
AO: EC use negatively changes the endothelial function. |
ARO: Observed effects with EC+ are caused by |
L: Relatively small number of studies and subjects; only acute effects evaluated (long-term use would be of interest). |
1 | ||||||
M |
Cross-sectional |
Subjects with chronic product use: • 42 Vapers (EC), 29 y, mean duration of EC use: 1.7 y, CotU: 923 ng/mL • 28 Smokers (CC), 34 y, mean duration of CC use: 10.2 y, CotU: 1,735 ng/mL • 50 NU, 28 y, CotU: 2 ng/mL |
Endothelial function (≈: not sign.) • • • Endothelial cell permeability in user sera: EC < CC ≈ NU |
AO: EC use can increase CVD risk and dual use can further increase the CVD risk. ARO: Misreports of product use history is possible. |
ARO: The authors’ |
L: Small group sizes; chronic EC use only 1.7 y (on average). G: No N-free EC group. |
? | ||||||
B |
Cross-sectional |
97,586 Male construction workers: • 23,885 NU • 5,014 SLT users • 8,823 Smokers (CC), ≥15 cig/d Duration of SLT use: 10–30 y (estimate) |
Sign. OR ( • • SBP > 160 mm Hg: SLT: OR=1.8/1.3 (in age groups: 46–55/56–65); CC: OR=0.8/0.7 |
AO: Also SLT use is associated with elevated risk for CVD. ARO: No verification of SLT only use. |
The authors cite evidence and conclude from their results that ARO: |
L: Only males included; healthy-worker-effect? No objective verification of SLT group. G: No other NGPs, no N-free group. |
1 / ? | ||||||
H |
Prospective | 120,930 healthy, never-smoking men (construction workers), enrolled 1971–1978 (BL), follow-up (health-checks) 1978–1993; follow-up cohort: 42,005 (normotensive at BL) |
• BL: 1.23 (1.15–1.33) • Follow-up: 1.39 (1.07–1.72) No clear dose-response |
AO: Snuff use increases the risk of hypertension. |
The authors cite evidence that |
L: No clear dose-response; tobacco habits rely on self-reports only; changes in habits are not assessed. |
0.5 / ? | ||||||
M |
Cross-sectional |
PATH study 2015–2016, 19,147 participants: • 8,783 NS (never CC or EC) • 183 CEV-NS (current EC, never CC) • 334 CEV-FS (current EC, former CC) • 3,938 FS (former CC) • 5,056 CES (current CC only) • 581 CDU (current dual) Duration of EC use: ~ 5 y (estimate) |
Prevalence of self-reported |
AO: Current EC use is similar to CC in terms of hypertension. ARO: Misclassification in product use possible (not verified) |
The authors cite evidence that use of N-free ECs were associated with higher BP reduction. ARO: |
L: Authors consider a number of limitations including dietary factors (not assessed) and (unreliable) self-reports. |
0.5 / 1 | ||||||
K |
Cross-sectional |
Community Health Survey, 2019, groups: • Dual users (EC and CC) • EC only users • CC only users Duration of EC use: 5–10 y (estimate) |
OR for Males: • Dual: 1.24* • EC only: 1.22* • CC only: 1.16* Females: • Dual: 1.44 • EC only: 1.41 • CC only: 1.35* *: p < 0.05 |
AO: Also EC and dual user have an increased risk for hypertension. ARO: Bias for misreport (particularly in female) is possible. No verification of product use. |
The authors cite evidence that ARO: Involvement of |
L: Small group sizes for EC users (particularly female); misreport of product use cannot be excluded. G: No N-free EC group. |
0.5–1.0 | ||||||
B |
Cross-over |
10 Healthy volunteers (smokers, 24–61y): • Smoking CC, 12 puffs, intervals of 45 s (1–1.3 cig), 9 min • Oral snuff, 2.5 g, 30 min • Chewing tobacco, avg 7.9 g, 30 min • Nicotine gum (NG), 2 pieces, 30 min Random order, 24 h between conditions |
Comparable increases in |
AO: N-related adverse effects also to be expected with the other N-products. |
(See left cell) ARO: All effects caused by |
L: Low number of subjects. G: No ‘sham’ experiments. |
1 | ||||||
V |
Cross-over |
15 SLT users, 18–33 y performed exercises under 2 conditions: • SLT, 2.5 g SLT: rest, 60%, 85% VO2max • Placebo: same exercises |
Cardio-respiratory responses: (SLT |
AO: SLT compared to placebo under workload increases HR and anaerobic energy production. |
The authors ascribe the observed (acute) effects to |
L: Only few and young males were investigated; only acute effects were studied. P: A study with long-term, older users including other NGPs would be of interest. |
1 | ||||||
B |
Cross-sectional |
135 Healthy men, 35–60 y : • 59 NU, 45.1 y • 47 SLT users, 44.3 y • 29 Smokers (CC); 47.2 y |
24 h- • Daytime Sign. positive correlation between CotP and BP in SLT, negative (not sign.) in CC. |
AO: Increases in HR and BP in CC and SLT were most likely due to the effects of Nicotine, in CC additional influences play a role. ARO: A few dual users were in the CC group. No verification of SLT only use. |
The author cite evidence that |
L: Small group sizes; only men. G: No other NGPs; no N-free EC. P: Studies avoiding these weaknesses would be of interest. |
0.5 / 1.0 | ||||||
M |
Cross-over |
33 Users of CC or EC were assigned to 3 conditions with > 4 weeks separation: • C1: EC with 1.2% • C2: EC without • C3: Sham (vaping without e-liquid) |
Fibrinogen? |
AO: Habitual EC use was associated with a shift in cardiac autonomic balance toward sympathetic predominance and increased oxidative stress, both associated with increased cardiovascular risk. |
Sympathomimetic effect after acute EC use is causally related to |
L: Small subject numbers; low |
1 | ||||||
B |
Cross-sectional |
Selected from 31 healthy subjects: • 9 NU (29 y) • 9 EC users (28 y, 2.1 y EC use) • 9 CC users (27.1 y, 7.3 pack x years) |
• • FDG uptake in spleen and aorta sign. trend of increase NU < EC < CC (indicator for spleenocardiac axis) |
ARO: Compliance status of EC users is unclear (although authors exclude dual use). |
ARO: Sympathomimetic effect of |
L: Very small group sizes; compliance unclear. |
0.5 / 1 | ||||||
R |
Cross-over |
• 9 Vapers (EC for > 3 months, no CC in last months), 28.5 y ; 4 conditions (separated by 1 week)
– 3 Types of CL (ciglike EC), 18 mg N/mL, 10 3-s-puffs at 26 s intervals – TEC (tank EC), 18 mg N/mL, same puffing pattern • 11 Smokers (CC for > 3 years), 26.2 y:
– 1 CC, 10 2-s-puffs at 28 s intervals (0.8 mg N/cig) |
• Nicotine in plasma: CC >> TEC > CL • |
AO: TEC are potential cessation products but also have an addiction potential (like CC and unlike CL). |
ARO: The results suggest that |
L: Small group sizes, only short-term EC users. G: No N-free condition, only HR no other physiological changes. |
1 | ||||||
S |
Cross-over |
30 Dual users (< 5 cig/d, > 1 mL e-liquid/d), performed 4 conditions (EC with 18 mg N/mL, 2 sessions, each 10 puffs every 30 s, PG/VG varied: • 1. 100% PG • 2. 55% PG • 3. 20% PG • 4. 2% PG |
• Nicotine in plasma: Higher in condition 1 and 2 • 100% PG less pleasant and satisfying |
AO: The PG/VG ratio must be also considered when evaluating the |
ARO: |
L: Small group sizes, only short-term EC users. G: No N-free condition, only HR no other physiological changes. |
0.5 / 1 | ||||||
H |
Longitudinal (6 weeks) | 50 Smokers (with schizophrenia and other mental disoders), 30 y, were provided with free ECs (4.5% |
Changes to BL at week 6: • −37% reduced CPD • 7% stopped • • |
AO: The provision of ECs is a potentially useful harm reduction intervention in smokers with a psychotic disorder. |
ARO: |
L: Small group size, only short-term effects were assessed. G: No N-free group. P: Patients with mental disorders might be a suitable group to investigate the long-term effects of EC (relatively high smoking rate). |
? | ||||||
S |
Cross-sectional | Meta-analysis of 14 studies, in total 441 participants: Healthy smokers and switchers to ECs |
Acute changes after EC use (* = sign.): • • • Changes after switching to EC: • HR: −0.03 bpm (3 studies) • SBP: −7.00 mm (3 studies) • DBP: −3.65 mm* (3 studies) |
AO: EC should not be labelled as CV safe. |
ARO: Effects could be caused partly of completely by |
L: Low number of studies and subjects. G: No separate evaluation for N-effects possible. |
0.5–1 | ||||||
P |
RCT |
186 Smokers (CC), African Americans/Latinx: 92/94, 43.3 y, 12.1 cig/d; randomized to • 125 EC use, 5% • 61 Controls (CC use as usual) |
Sign. changes EC • NNAL • COex No sign. changes EC • Cotinine in urine • Respiratory symptoms (weeks 2 and 6) • • • Significances similar in EC only users |
AO: ECs may be an inclusive harm reduction strategy for this population. ARO: 58–68% in EC group were dual users, 4% were CC only users in EC group. Compliance was not enforced. |
ARO: All EC contained 5% |
L: Only short- to medium-term study (6 weeks). G: No N-free EC group. P: Long-term study (> 1 year) including an N-free EC group would be of interest. |
? | ||||||
B |
Cross-over | 20 Smokers (CC) were assigned to CC, EC and HTP, with 1 week wash-out periods. One unit of each product was used (1 CC, 9 puffs of EC, 1 stick of HTP). |
Biomarkers in blood were measured before and after product use: • • • • • • • • • • All changes were sign., except NO and Vitamin E after HTP; CC use showed the largest changes |
AO: Acute effects of HTPs, ECs, and CCs are different on several oxidative stress, antioxidant reserve, platelet function, cardiovascular, and satisfaction dimensions, with CCs showing the most detrimental changes in clinically relevant features. |
ARO: Involvement of |
L: Too short study duration. G: Condition EC without nicotine is missing. P: Long-term study (> 12 months) with larger group sizes (> 100/group) and an additional condition (EC without nicotine). |
? | ||||||
M |
Cross-over |
24 Smokers (CC for > 1 y), 30.9 y, were allocated to 4 conditions: • 1. EC (36 mg N/mL), 2 sessions with 10 puff, separated by 20 min • 2. EC (0 • 3. CC (10 puffs, own brand) • 4. Nicotine inhaler (10 mg |
• • |
ARO: Incomplete reporting, abstinence (prior to experimental sessions) doubtful (according to the authors). |
ARO: It can be deduced that |
L: Only smokers were investigated, small group, incomplete reporting (only HR, no results on BP). P: A larger study with (long-term) EC users and more physiological measurements would be of interest. |
1 | ||||||
B |
Cross-over |
36 Dual users of CC and EC were investigated in the clinic under three conditions: • C1: • C2: • C3: abstinence from nicotine |
• • • Urinary biomarkers: • Blood biomarkers: • |
AO: CC and EC had similar patterns of hemodynamic effects compared with NU, with a higher average HR with CC |
ARO: Involvement of nicotine in observed effects is possible but cannot be evaluated (EC without nicotine is lacking). |
L: Too short study duration. G: Condition EC without nicotine is missing. P: Long-term study (> 12 months) with larger group sizes (> 100/group) and an additional condition (EC without nicotine). |
? | ||||||
G |
Various (systematic review) |
19 Studies evaluated,: • Smokers (CC) • Vapers (1. generation ECs, with • Vapers (1. generation EC−, without |
Acute CV effects (sign. diff.) CC • • • EC+ • ΔHR (4 studies): +6.44 bpm • ΔSBP (5 stud.): +3.73 mm Hg • ΔDBP (5 stud.): +3.25 mm Hg HRV for CC Sign. increased |
AO: EC are sympatho-excitatory, the effect is lower for the 1. generation ECs compared to CCs. |
ARO: The effects are caused (completely?) by |
L: Studies were done with 1. generation of ECs only. P: Similar studies with newer generations of ECs and also other NGPs. |
1 | ||||||
H |
Cross-over |
32 Vapers (EC use since > 3 months, partly CC), 25.6 y, were allocated to 4 EC conditions, separated by 48 h: • 1: 0.5 Ω/3 mg N/mL • 2: 0.5 Ω/8 mg N/mL • 3: 1.5 Ω/3 mg N/mL • 4: 1.5 Ω/8 mg N/mL 10 puffs at 30 s intervals, from min. 70 to 130: |
Changes by condition: • Plasma • • Puff number ( |
ARO: Changes in topography and physiology (HR) follow the nicotine delivery. |
ARO: Increase in HR directly dependent on |
L: Only acute effects were studied; relatively young subjects; 14 vapers were naive to sub-ohm ECs. P: Study with older, long-term users, extension to other CV paramters: BP, FMD, PWV, AI. |
1 | ||||||
I |
Cross-over and cross-sectional |
• 37 CC users, 26.7 y • 43 EC users (self-reported), 28.0 y • 65 NU, 21–45 y Groups allocated to • CC (1 CC in 7 min)/straw (CC group only) • ECN (with 1.2% • Nicotine inhaler (NI)/straw (EC and NU) |
• • |
AO: If one does not currently smoke, one should not use ECs due to adverse CV effects. NI only slightly increase plasma ARO: Unclear how long EC was used in EC group. |
ARO: Use of EC with |
L: Small groups, only young subjects, EC use duration not provided. P: Larger study with long-term EC users would be of interest. |
1 | ||||||
ECG-indices: only partial influence of |
||||||
0.5 | ||||||
G |
Cross-over |
15 NU, healthy, 21 y, were assigned to 2 conditions: • EC(+) with • EC(−) without, same puffing profile, 0 mg N/mL Conditions were separated by ~1 month; measurements were done before (BL), during and after vaping (recovery), each for ~10 min |
Sign. changes occurred only in EC(+) condition: • • • All changes lasted into the recovery phase |
AO: Suggest that the decrease in MSNA is mediated by an intact baroreflex (resulting from the increase in MAP) in the healthy young subjects. In older population |
ARO: The results suggest the CV effects were caused by |
L: Very small number of subjects; changes after only one use of product was investigated; very young population. G: Data allow no deduction of a dose-response relationship for P: A study with long-term EC users avoiding the weaknesses would be of interest. |
1 | ||||||
C |
Longitudinal (12 weeks) | 40 Smokers (schizophrenics), 48.3 y, 28 cig/d, were provided with ECs for free for 12 weeks |
37 vapers decreased CPD from 28 (BL) to 6.4 cig/d (12 weeks and 6 months); |
ARO: EC group was actually a dual user group. |
ARO: Role of |
L: Small group size, only medium term effects can be observed. G: No N-free group. P: Schizophrenics might be suitable group to investigate the long-term effects of EC (very high smoking rate). |
? | ||||||
E |
Cross-sectional |
• 18 NU, male, 24.4 y • 21 Snuff users, male, 24.1 y, duration of snuff use: 7.0 y • 19 Smokers (CC), male, 25.3 y, duration of CC: 9.1 y |
Sign. diff. in CVD-related BOBEs (≈ : not sign.): • • • • • • Not sign. diff. between groups: |
AO: Snuff use has similar but lower effects on CVD-related BOBEs, except for lipids. ARO: Use of snuff only not verified. |
The authors cite evidence that NG use does not affect lipids and that CC-related hyperlipidemia is not due to ARO: |
L: Small group sizes; only very young men included. G: Other NGPs (EC, HTP), N-free EC. P: Larger study with older subjects, including additional NGPs would be of interest. |
? | ||||||
S |
Cross-sectional |
1,061 Baseball players (mostly 20–29 y): • 477 SLT users • 584 NU CC excluded |
No sign. difference SLT • • • • • |
AO: SLT use has at most a modest effect on CVD risk factors. ARO: No verification of SLT use. |
The authors cite evidence that ARO: Results suggest that |
L: Only young and fit subjects included. G: No other NGPs. |
0 / ? | ||||||
E |
Cross-sectional |
Swedish men, 25–64 y : • 124 Smokers (CC) • 130 Ex-CC • 92 Snuff dippers • 38 Snuff+CC • 220 NU |
BMs for fibrinolysis (t-PA, PAI-1, • CC: Fibrinogen sign. increased No sign. diff. for other groups and BMs |
AO: Snuff use does not appear to affect potential CVD risk factors. ARO: Possibility of mis-report and -classification of product use. |
The authors cite evidence that ARO: |
L: Relatively small group sizes; only male snuff users. |
0 / ? | ||||||
M |
Cross-over (longitudinal) | Smokers (CC, 10 m/17 f, 35 y/38 y), 29 cig/d, stopped CC at day 0, NRT (N-patch) until day 35, no CC and NRT until day 77 Non-smokers (NU, 7 m/9 f, 42 y/40 y) |
• Day 0: NU > CC • Day 35: no change in HDL • Day 77: CC: increase in HDL to NU levels Weight gain: • Day 35: no changes • Day 77: increase in CC (f) |
AO: |
AO: see left column. Evidence is cited that weight gain occurs in long-term NRT users. ARO: HDL increase: 1 ARO: Weight gain: 1/0 |
L: Small sample sizes; only short-term NRT use. G: No other NGPs tested, in particular EC with/without P: Long-term study including NGPs would be of interest. |
M |
Cross-sectional |
• 16 Habitual EC users, 28.6 y, EC use: 241 min/d, EC use duration: 1.6 y • 18 NU, 26.6 y |
• • |
AO: EC use increases the risk for CVD. ARO: Some CC use cannot be excluded (also conceded by the authors). |
The authors cite evidence that ARO: An effect of |
L: Small sample sizes; only young subjects; short period of EC use. G: no other NGPs studied; no group with N-free ECs. P: A study avoiding these weaknesses would be of interest. |
0.5 / ? | ||||||
L |
Cross-over (longitudinal, 90 d) |
160 Smokers (CC menthol), randomized to: • 78 HTP (menthol, 1.21 mg N/stick), 39.2 y • 42 CC (menthol), 33.7 y • 40 Smoking abstinent (SA), 38.8 y 5 d confined, 85 d ambulatory conditions |
Sign. improvement after 90 d • No sign. diff. HTP • All BOBEs were not sign. diff. between HTP |
Compliance (checked with COex < 10 ppm for HTP and SA) was high: 89.7% (HTP), 97.6% (CC), 92.5% (SA). Dual use (HTP + CC): 2.6% AO: The reductions in HTP users were promising and reached almost the levels in the SA group. |
ARO: |
L: Low actual compliance in HTP and SA group after 90 d (could have spoiled the results); 3 months might be too short for biological effects. P: Larger and longer study with better compliance would be of interest. |
? | ||||||
W |
Cross-over (longitudinal, up to 24 months) |
206 Users of CCs and ECs were switched to vaping (EC, 1.6 % Follow-ups (FUs) at 1, 3, 6, 12, 18 and 24 months; 102 subjects completed the study. |
No clinically relevant adverse effects (AE) were observed during the 24 months study. No consistent changes over time were observed for EC-compliant subjects: |
Authors’ definition: “EVP-compliant subjects” were defined as subjects who were abstinent from CCs for “at least 80% of the completed study days.” |
ARO: |
L: Compliance criteria not sufficient to see effects. G: Control groups are missing: CC, NU. |
? | ||||||
H |
Cross-over (longitudinal, 90 d) |
160 Smokers (CC), randomized to: • 80 HTP (menthol, 1.21 mg N/stick), 39.2 y • 41 CC (menthol), 33.7 y • 39 Smoking abstinent (SA), 38.8 y 5 d confined, 86 d ambulatory conditions |
Sign. improvement after 90 d compared to CC: • No sign. diff. HTP • All BOBEs were not sign. diff. between HTP |
Compliance (checked with COex < 10 ppm): 51% in HTP group, 18% in SA group. AO: The reductions were promising with respect to health risk reduction. |
ARO: |
L: Low actual compliance in HTP and SA group after 90 d (could have spoiled the results); 3 months might be too short for biological effects. P: Larger and longer study with better compliance would be of interest. |
? | ||||||
F |
Cross-sectional |
• 94 NS, 29 y • 285 CC, 32 y • 36 EC, 29 y • 52 Dual, 33 y |
Vascular measures sign. diff. between groups: • Carotid-femoral • Carotid-radial • • • No sign. diff.: • • |
AO: EC use is not associated with a more favorable vascular profile. ARO: No information on EC use duration. |
ARO: |
L: Most groups too small. G: No information on EC use duration; EC without |
0.5 / ? | ||||||
K |
Cross-sectional |
All men: • 337 Dual users (CC + EC), 36.7 y, CotU: 1,303 ng/mL, 15.1 cig/d • 4079 CC only, 46.3 y, CotU: 1,236 ng/mL, 14.8 cig/d • 3,027 Never smokers (NS), 39.8 y, CotU: 0.7 ng/mL |
Sign. diff. of dual users to other groups: • • • • • • |
AO: Given that most EC users are dual users and dual users are more vulnerable to CV risk factors than CC-only smokers and NU, more active treatment for smoking cessation should be considered with priority. ARO: Proportion of EC use in dual users appears low. |
ARO: Role of |
L: EC only group is missing. |
? | ||||||
M |
Cross-sectional |
• 104 Never users, 29 y, CotU: 3 ng/dL • 290 CC users, 33 y, CotU: 927 ng/dL • 42 Sole EC users, 28 y, CotU: 686 ng/dL • 47 Dual (EC+CC) users, 33 y, CotU: 851 ng/dL • 23 Sole pod users, 26 y, CotU: 970 ng/dL (pods are new generations of ECs) • 19 Dual pod users, 24 y, CotU: 508 ng/dL |
Sign. diff.: • NU • NU • NU • CC • NS • NS |
AO: Overall, users of early generation electronic cigarettes display adverse metabolic profiles. In contrast, pod-based electronic cigarette users have similar lipid profiles to never users. ARO: Duration of use of ECs and pods not provided (probably shortest in pod users). |
ARO: Relative high cotinine levels in pod users and lack of sign. diff. to NS suggest only a minor (if any) role of |
L: Duration of EC/pod use was least 3 months, but might be too short. G: Role of |
0–0.5 | ||||||
G |
Cross-over (longitudinal, 180 d) |
Healthy current smokers (CC) were allocated to 3 groups: • 59 CC (continue smoking), 17.9 cig/d (at 180 d) • 127 HTP use, 21.9 sticks/d (at 180 d) • 109 Cessation (NU) 40 Never-smokers also included |
Sign. diff. HTP • No sign. diff. HTP • |
AO: Larger studies are needed for evaluating the risk reduction. ARO: Compliance was approved by CEVal: 76% of HTP and 73 % of NU group (180 d). |
ARO: |
L: Too short durations o HTP use. G: No comparisons of NU P: A larger and longer study would be of interest. |
? | ||||||
A |
Cross-sectional |
324 Healthy participants, 21–45 y • 65 NU, CotU: 3 mg/dL • 19 EC users, CotU: 826 mg/dL • 212 Smokers (CC), CotU: 854 mg/dL • 28 Dual users, CotU: 910 mg/dL |
Number of sign. changes in • EC: 2 • CC: 4 • Dual: 6 No sign. diff. when EC and Dual groups were compared to CC |
AO: EC use is associated with higher endothelial inflammation. ARO: Product habits rely on self-reports (no verification). |
ARO: |
L: Small group sizes; self-reports only for product habits; temporal issues (cross-sectional study). G: No N-free EC group. |
? |
Author, year, country (Ref) | Study type | User groups / duration of product use | Endpoints and findings | Comments (bias, compliance, etc.) | Conclusions regarding nicotine's ( |
Limitations (L) / Gaps (G) / Proposals (P) |
---|---|---|---|---|---|---|
B |
Prospective |
Male construction workers, up to 65 y (1970/71), follow-up after 12 y for mortalities: • 32,546 NU • 6,297 SLT users • 14,983 Smokers (CC1), < 15 cig/d • 13,518 Smokers (CC2), ≥ 15 cig/d Duration of SLT use: 10–30 y (estimate) |
RR (CI) compared to NU: • – SLT: 1.4 (1.2–1.6) – CC1: 1.8 (1.6–2.0) – CC2: 1.9 (1.7–2.2) • – – CC1: 1.5 (1.3–1.8) – CC2: 2.5 (2.2–2.0) • – SLT: 1.4 (1.3–1.8) – CC1: 1.7 (1.6–1.9) – CC2: 2.2 (2.0–2.4) |
AO: Both CC and SLT users have an increased risk for CVD, risk for SLT is lower. ARO: SLT (only) use was not verified, dual use is not unlikely. |
The authors cite evidence that ARO: |
L: Only male workers (healthy-worker effect?); dual use (SLT + CC) is possible. G: Other NGPs; ECs without |
0 / ? | ||||||
A |
Prospective |
NHANES I (BL), 20 y-follow-up: • 5,192 NU (no tobacco), 47.8 y • 505 SLT (exclusive), 54.0 y • 5,523 CC (exclusive), 44.9 y |
Hazard ratio for SLT • • • Dual use did not increase all cause mortality beyond the sum of CC and SLT risks. • Borderline increase in SLT (f) for all cancers (not sign.) |
AO: See a limitation that only ever use of SLT could be included in the study. ARO: Use pattern could have changed during the 20 y of follow-up. |
ARO: Overall results suggest that |
L: SLT use not completely assessed. G: No other NGPs included. P: Future evaluations of NHANES data could include NGPs. |
0 / ? | ||||||
A |
Case-control |
• 123 Pancreatic cancer cases • 682 Matched controls All non-CC users (life-long) Duration of SLT use: 10–30 y (estimate) |
OR for • Cigar (ever/only): 1.7/1.9 • Pipe (ever/only): 0.6/0.3 • SLT (ever/only): 1.4/1.1 All ORs not sign. SLT: sign. (p = 0.04) trend with amount/d |
AO: Suggest that heavy use of SLT may increase risk for pancreas cancer. ARO: Compliance with product use was not checked. |
ARO: Most probably, TSNAs play a role. Involvement of |
L: Product use relies on self-reports, past tobacco history may be questionable |
0–0.5 | ||||||
M |
Prospective |
Lung Health Study (substudy), 3,320 subjects (smoking intervention with NRT, • 1,986 NRT users, mean age 48 y • 1,329 no NRT users, mean age 48 y • Unclear what the CC group during 5-year surveillance is |
Cancer risks: • CC: sign. increase • NRT: not sign. • • |
AO: Despite short FU time period, smoking predicted cancer in this analysis and nicotine replacement therapy did not. ARO: Danger of misreports of product use (CC, NRT) and abstinence. |
The authors cite genetic evidence that |
L: Small number of cancer cases; short FU period; unclear CC group; low G: Nicotine inhaler not studied (of interest for lung cancer). |
0 / ? | ||||||
C |
Cross-sectional |
• 9 Smokers (CC), 42.2 y, CotU: 5.87 ng/mL • 15 Vapers (EC, all containing • 21 Ex-smokers, 43.0 y, CotU: 1.23 ng/mL, quit CC since 67.0 months |
468 (of 3,165) genes varied between EC and Ex-CC, 79 of these were in accordance with CC; downregulated genes in EC were mostly also downregulated in cells exposed to EC aerosol. |
AO: Pattern of EC is closer to former CC than to current CC users. ARO: No check of dual use (CC and EC) was performed. ARO: CotU in CC and EC appears much too low (μg/mL?). |
ARO: Role of |
L: Small group sizes. G: No N-free EC group; also no initial EC user group (only former CC users who switched to EC). |
? | ||||||
F |
Observational study (longitudinal) |
At BL: • 469 CC users, ≥1 cig/d, ~50 y • 228 EC users, ≥50 puffs/week, ~50 y • 215 Dual users, ~50 y FU after 6 y |
Incidence of Not sign. diff. between 3 groups |
AO: That there was no evidence for harm reduction in EC only or dual users after 6 y. ARO: Possibility of mis-reports of product use (COex in only 50% of subjects). |
ARO: |
L: Small group sizes; misclassification not excluded. G: No N-free EC group. |
? | ||||||
C |
Cross-sectional |
• 15 Vapers (EC), 29.3 y, EC but no CC use for at least 6 months • 15 Smokers (CC), 29.5 y, CC use for at least 1 year • 15 Controls (NU), 28.9 y |
• 5-mC in LINE-1: NU* > EC ≈ CC • 5-hmC (global): NU* > EC ≈ CC *: sign. diff. from other 2 groups Expression levels of various DNA methyl transferases: not sign. diff. between groups. |
AO: In conclusion, we have demonstrated, for the first time, key epigenetic modifications, including hypomethylation of LINE-1 repeat elements and global loss of DNA hydroxymethylation, in a well-defined population of exclusive vapers (EC) and smokers (CC) relative to controls. ARO: Dual users excluded (but only COex and COHb applied for approval). |
ARO: |
L: Small group sizes; no objective check of dual use; changes in peripheral leukocytes may differ from those in target cells. G: No inclusion of N-free EC group. P: Larger study with similar endpoints but inclusion of an N-free EC group. |
? | ||||||
R |
Cross-sectional |
• 116 EC users, 20.9 y, e-liquid consumption: 7.8 mg/d, 5.6 mg N/mL • 117 CC users, 22.8 y • 117 NU, 20.6 y |
• EC were distinct from CC • Biological aging profile: EC more similar to NU than CC • EC profile did not discriminate between lung cancer from normal tissue (CC profile did) • EC profiles did not replicate in independent samples |
AO: DNA methylation profiles are clearly distinct from CC. ARO: Relationship to chronic effects are not yet clear. |
ARO: Role of |
L: Very young population; only short durations of products use possible. G: No N-free EC group. P: Endpoints may be of interest when more data are collected. |
? | ||||||
H |
Longitudinal (3 visits over 3 weeks) | 3 Vapers (EC, 6 mg N/mL), had not smoked for 2 months: 20 EC puffs/visit, 3 visits; blood and buccal cell samples taken before and after EC use |
|
AO: A single EC use can modify gene expressions (towards a cancer risk). |
ARO: Role of |
L: Extremely small group. G: No N-free EC group. P: Perform larger study including CC group, N-free EC group; investigate effects after long-term (chronic) use. |
? | ||||||
A |
Cross-sectional |
• 269 Controls, NU, 30.4 y • 22 Control subgroup, NU, 33.5 y (= controls who had BOEs measured in urine) • 112 Smokers (CC), 41.2 y • 35 Vapers (EC), 23.5 y • 19 SLT users, 36.6 y |
CC had sign. lower |
AO: Methylation extent of cg05575921 together with CEMA is suitable to distinguish CC from other NGP users. ARO: The same can be achieved by CEMA alone! |
ARO: |
L: Small group sizes; short product use durations. |
0 |
Author, year, country (Ref) | Study type | User groups / duration of product use | Endpoints and findings | Comments (bias, compliance, etc.) | Conclusions regarding nicotine's ( |
Limitations (L) / Gaps (G) / Proposals (P) | |
---|---|---|---|---|---|---|---|
M |
Cross-sectional |
Healthy adults, 18–50 y • 13 NU, 30.4 y, CotS: 0.08 ng/mL • 12 EC users, 28.7y, CotS: 200.7 ng/mL, predominantly used EC in last 6 months • 14 Smokers (CC), 30.7 y, CotS: 159.0 ng/mL |
• 53 genes common in CC and EC • 305 additional genes in EC |
AO: EC use leads to immune suppression in the nasal mucosa. ARO: Dual users were excluded, but not verified. |
ARO: |
L: Small group sizes; probably only short use duration of EC; relatively young subjects. G: No N-free EC group. |
|
? | |||||||
C |
Cross-over (longitudinal, up to 1 y) |
134 Smokers (CC) were assigned to ECs with: • A: 49 subjects, 2.4% • B: 45 subjects, 2.4% • C: 40 subjects 0% For final evaluation, subjects were classified into: • Failures (F): continued CC, not meeting criteria for reducers (R) or quitters (Q) • R: reduced CC by ≥50% • Q: no CC, COex<7ppm |
• FeNO: stayed at BL level for F and R groups, sign. increased for Q • COex after 52 weeks: F > R > Q |
AO: Switching from CC to EC can revert harm in the lung. |
ARO: Unfortunately, data were not evaluated to EC N-content. |
L: Small group sizes; no evaluation by N-content. P: A larger study avoiding the weaknesses would be of interest. |
|
? | |||||||
M |
Cohort study (FU after 12 months) |
2,086 Adolescents (16–18 y) • 502 Ever EC users (past users) • 201 Current EC users (EC use in last 30d) |
OR (CI) for • Past EC: 1.85 (1.37–2.49) • Current EC: 2.02 (1.42–2.88), become insign. after adjustment for life-time CC use OR not increased for wheeze after adjustment for CC. |
AO: EC use increases risk for bronchitis in adolescents. ARO: EC only use not verified (authors also concede confounding by CC). |
ARO: |
L: Possibly insufficient assessment of CC use in EC groups. |
|
? | |||||||
P |
Longitudinal (42 months) |
• 9 Vapers (EC), 26.6 y, 0.0–1.8% • 12 NU, 27.8 y |
No sign. changes between BL, 12, 24 and 42 months for: • • • • • • • • • |
AO: EC long-term use is not associated with health concern in young users. ARO: Non-compliant subjects were excluded (but no objective prove for compliance). |
ARO: |
L: Very small groups; use of only 1. generation of EC with probably low G: No N-free EC group. P: A larger study including N-free EC group would be of high interest. |
|
? | |||||||
P |
Longitudinal (36 months) |
• 22 Smokers with COPD, switched to EC, 65.2 y • 22 Smokers with COPD, continued CC use, 66.5 y |
BL, and follow-up (FU) at 12, 24 and 36 months • CC group: CPD almost unchanged at 20 cig/d; no sign. change in • EC group: decrease in CPD (20 to 1.5 cig/d); sign. improvements in lung function and walk distance Also improvements in dual users |
AO: EC use ameliorates COPD outcomes and might also reverse the harm of some smoking effects. ARO: Although dual use was evaluated separately, compliance is an open question. |
The authors speculate that |
L: Small group sizes. See also Polosa |
|
?/0 | |||||||
ARO: From the study data, the role of |
|||||||
? | |||||||
L |
Cross-over (acute) |
• 27 healthy smokers (H-CC), 23.0 y • 27 smokers with mild asthma (MA-CC), 23.0 y Both groups performed a control (EC without liquid) and vaping session (e-liquid with 12 mg/mL |
• Control session: no changes • EC session: acute increase in |
AO: One EC session has acute mechanical and inflammation effect on the respiratory tract (larger in smokers with MA). |
ARO: |
L: Only acute effects of EC smokers were investigated. G: No N-free group included. |
|
? | |||||||
S |
Cross-over |
10 NS were assigned to one of 2 conditions: • C1 (N=7): • C2 (N=3): BM measurements pre and 30 min after vaping |
Observed changes (post • C1: EMPs elevated, • C2: No changes found |
AO: This study provides |
ARO: Effects were found only after exposure to EC with |
L: Very low subject numbers, only acute effects were investigated, which were completely reversible. G: No information available whether chronic use of N-products can lead to persistent changes. |
|
1 | |||||||
M |
Cross-sectional |
• 30 Vapers (EC), males, 27.1 y, former and current CC or tobacco users were excluded; self-reported EC use for > 6 months • 30 NU, males, 25.9 y, former CC and tobacco users were excluded; self-reported |
Sign. lower in EC • • • Not sign. diff.: • • • |
AO: EC use impairs lung function. ARO: Product use status replies on self-reports, not objectively approved. |
ARO: |
L: Small groups, only short- to medium term use. G: No N-free EC group; no CC group (as a positive control). |
|
? | |||||||
C |
Cross-over |
30 NS performed one • 5 min EC session (1.8% • 5 min CC session (0.6 mg N/cig) |
• • • |
AO: EC use may be dangerous for CC smokers. ARO: AO appears at least questionable. ARO: Only short term use and effects were observed. |
ARO: |
L: Only short-term use was investigated. G: No N-free EC condition included. P: A study with long-term EC users (included N-free) would be warranted. |
|
? | |||||||
R |
Cross-sectional |
• 16 NU, 29.6 y, CotP: 0.06 ng/mL • 17 CC, 31.8 y, 10.5 cig/d, CotP: 184 ng/mL • 16 EC, 28.3 y, 218 puffs/d, CotP: 218 ng/mL |
• • • • • • • |
AO: EC use alters the profile of innate defense proteins in airway secretions. ARO: Only self-reports for product use, not objectively verified. |
ARO: |
L: Small group sizes, no verification of product use, short EC use? G: No other NGPs, no N-free ECs. P: Improved study with these endpoints would be of interest. |
|
? | |||||||
G |
Cross-sectional |
• 18 NU, 27.3 y • 13 CC, 34.0 y: 9.5 pack-years, 10.1 cig/d (last 2 weeks) • 10 EC, 26.8 y: last 2 weeks: 44.1 puffs/d, 11.4 mL e-liquid/d |
|
AO: EC use has long-term effects on the lung, possibly mediated by PG/VG. ARO: Unclear for how long ECs were used. |
ARO: Effect of N cannot be excluded. Effects of PG/VG alone also possible. |
L: Small group sizes, long-term use (in EC users) is not well defined. P: Proteome study with long-term users would be of interest. |
|
0.5 / ? | |||||||
W |
Cross-over |
206 Users of CCs and ECs were switched to vaping (EC, 1.6% Follow-ups (FUs) at 1, 3, 6, 12, 18 and 24 months; 102 subjects completed the study |
No clinically relevant adverse effects (AE) were observed during the 24 months study No consistent changes over time were observed for EC-compliant subjects: |
Authors’ definition: “EVP-compliant subjects” were defined as subjects who were abstinent from CCs for “at least 80% of the completed study days.” |
ARO: |
L: Compliance not sufficient to see effects. G: Control groups are missing: CC, NU. |
|
? | |||||||
G |
Cross-sectional |
• 14 NU, 25.8 y • 14 CC, 29.5 y: 9.5 pack-years, 10.1 cig/d (last 2 weeks) • 14 EC, 26.1 y: last 2 weeks: 44.1 puffs/d, 11.4 mL e-liquid/d |
|
AO: EC users are at increased risk for chronic lung disease. ARO: Unclear for how long ECs were used. |
ARO: |
L: Small group sizes, long-term use (in EC users) is not well defined. P: Study of anti-protease/protease balance in NGP long-term users (EC, HTP) would be of interest. |
|
0.5 / ? | |||||||
K |
Cross-over |
20 Smokers (CC), assigned to two conditions, separated by 24 h: • C1: Vaping, 15 puff, EC with • C2: Smoking 1 CC ad lib |
Acute biomarker changes pre/post, sign. for C1 and C2: • • • Sign. change only in C2: • Sign. change only in C1: • No sign. change (C1 or C2): • |
AO: These findings suggest that both electronic cigarettes and tobacco smoking negatively impact vascular function. |
ARO: Involvement of |
L: Small group sizes, only acute changes. G: No condition EC without |
|
0.5 | |||||||
Sign. role of |
|||||||
0 | |||||||
Role of |
|||||||
? | |||||||
A |
Cross-over |
15 Occasional smokers (< 10 CC/month): Cross over of two conditions separated by 1 week: • • |
Vascular measurements over 4 h: • Respir. measurements over 6 h: • No sign. diff. + • FeNO sign. increased in EC (+/−N) • VC sign. decreased in EC (+/−N) |
AO: ECs with |
ARO: |
L: Small group sizes; only acute effects investigated. P: Investigate long-term effects in users of EC with and without |
|
0.5 – 1 | |||||||
C |
Cross-over |
25 Occasional smokers (CC) were assigned to 3 conditions (random order): • Sham vaping (EC switched off) • EC with • EC without 20 Heavy smokers (CC): • 10 assigned to sham EC • 10 assigned to EC without Vaping: 25 puffs at 30 s intervals, 4 s inhalation |
• • • • |
AO: Effect on PO2 is caused by PG/VG in ECs rather than |
ARO: |
L: Results are valid for intense vaping under acute conditions only with a low number of subjects. P: A larger study under long-term, realistic use conditions would be of interest. |
|
0 | |||||||
T |
Cross-sectional |
• 12 Never-smokers (NS), 26 y • 15 Vapers (EC), 27 y: 80% were former smokers, duration of EC use (average, range): 3 (0.5–4) y, 127 puff/d, 7 mL e-liquid/d, N-content: 12 (1.5–36) mg/mL • 16 Smokers (CC), 26 y |
Sign. diff.: a: NS Total cells: b |
AO: Suggest to also investigate NS who started EC use (in order to avoid the influence of former smoking) and to study the role of ARO: EC were relatively well characterized. EC use was relatively short. |
ARO: The observation that EC users were close to never-smokers suggests that |
L: Small group sizes; relatively short duration of EC use. G: No cessation group, no group using N-free ECs. |
|
0 / ? | |||||||
V |
RCT |
263 Smokers (CC) at baseline assigned to replace CC progressively by • EC (N = 191, 3 groups: 0, 6, 36 mg/mL • EC-dummy (fresh air) (N = 72), 18.1 cig/d at BL: after 1 month: −5 cig/d, after 3 months: −6 cig/d |
Lung function parameters • • • • • • and • • • were not sign. diff. between EC and fresh air at BL, 1 and 3 months |
AO: EC use sign. contributes to health outcome. ARO: Amount of CC used by the two groups might be too high to see an effect. |
ARO: No effects were observed, therefore, role of |
L: Sensitivity of the measured study parameters might be too low; study duration might be too short. |
|
? | |||||||
O |
Cross-sectional (BRFSS) |
402,822 Never CC users: • 399,719 NU (no CCs or ECs), median age group: 45–49 y • 3,103 EC only users, median age group: 18–25 y (!) Duration of EC use: ~ 5 y (estimate) |
OR for self-reported • Occasional EC: 1.31 (1.05–1.62) • Daily EC: 1.73 (1.21–2.48) |
AO: EC use is a risk factor for asthma (to be approved in future longitudinal studies). ARO: Dual use cannot be excluded. |
ARO: |
L: EC use not further characterized; EC users much younger than NU; self-selection (to use ECs because of asthma) possible. |
|
? | |||||||
P |
Cross-sectional (PATH) |
32,320 Adults: Propensity matching: • 2,727 EC users • 2,727 NU Duration of EC use: < 10 y (estimate) |
OR (CI) for self-reported |
AO: EC use is associated with COPD in adults, long-term studies are required. ARO: Confounding is possible. |
Possible ARO: |
L: Data rely on self-reports; confounding possible (EC used started after diagnosis?); duration and dose of EC not considered. G: No long-term use of ECs. |
|
? | |||||||
B |
Cross-sectional (chronic (BL) and acute) |
• 30 Smokers (CC), 23.2 y, CC since 50 months, 0.6 mg/cig, 6.2 cig/d • 30 Vapers (EC), 22.2 y, EC since 29 months, 12 mg N/mL, 15.6 sessions/d • 30 Dual (CC/EC), 22.3 y, since 67.3/27.7 months, 0.6/12 mg • 30 NU, 22.9 y |
• – BL: NU > CC ≈ Dual ≈ EC – 1 m: NU > CC ≈ Dual ≈ EC – 30 m: CC ≈ Dual < EC • – BL: no clear diff. between groups(same after acute exposure 1 and 30 min) |
AO: EC use is similar in terms of reduced airflow (PEF) and FeNO as smoking. ARO: Long-term use was not well assessed. Changes in terms of lung function are variable. |
ARO: |
L: Long-term use of EC (> 2 y), but compliance not well assessed. G: No long-term, N-free EC group. P: Long-term study with these groups (+ N-free EC) would be of interest. |
|
? | |||||||
L |
Cross-sectional |
58,336 Adolescents, 12–18 y Self-reported tobacco/N use: • 49,542 NU • 4,496 CC only users • 540 EC only users • 51 HTP only users • 2,344 Dual users (CC + EC) |
Sign. increased OR (NU = 1): • • Allergic rhinitis: none • Atopic dermatitis: CC, (EC), dual |
AO: Any product use might be risk for the indicated allergic diseases, however, longitudinal studies are required. ARO: No verification of product (only) use. |
ARO: |
L: Some groups are very small (EC, HTP); high probability of dual/multi use in the “only” groups; very young subjects and short product uses. G: No N-free EC group. |
|
? | |||||||
G |
Cross-sectional (5 studies), prospective (1 study) |
Review of 6 epidemiological studies with former CC users who switched to ECs Duration of EC use: < 10 y (estimate) |
EC • 3 Studies on RD ( • 3 Studies on |
AO: Switching to ECs reduces risk for RD but does not change risk for CVD. ARO: General issue with misclassification in epidemiological studies. |
ARO: |
L: Low number of studies, problem of misclassification. G: No N-free EC group. P: Authors emphasize need for prospective studies and RCTs. |
|
? | |||||||
S |
RCT |
• G1: 15 NU (< 100 CC in lifetime, no EC in past year) • G2: 15 NU switched to EC without |
Biomarkers in • Biomarkers in bronchial brush: • |
AO: Although limited by study size and duration, this is the first experimental demonstration of an impact of e-cig use on inflammation in the human lung among never-smokers. ARO: G2 had sign. elevated PG levels in urine after EC use. |
ARO: Role of |
L: Too short use of ECs; low numbers of subjects in both groups. P: Long-term study (> 12 months) with larger group sizes (> 100/group). |
|
? | |||||||
S |
Cross-sectional |
• 42 Never-smokers, 25 y • 15 EC users, 27 y: 80% were former smokers, duration of EC use (average, range): 2.6 (0.5–4) y, 163 puff/d, 8.3 mL e-liquid/d, N-content: 10.7 (1.5–36) mg/mL • 16 Smokers (CC), 26 y |
Level in EC group mostly between NS and CC (closer to NS): Cells in Sign. diff: a: NS • • • • • • Differential |
AO: Suggest to also investigate former smokers without switching to ECs. ARO: EC were relatively well characterized. EC use relatively short. |
ARO: The observation that EC users were close to never-smokers suggests that |
L: Small group sizes; relatively short duration of EC use. G: No cessation group, no group using N-free ECs. |
|
0 / ? | |||||||
A |
Cross-sectional |
61 College students: • 32 self-reported EC use in the last 30 d, 34.4% reported CC use in last month • 29 NU in the last 30 d, 10.3% reported CC use in last month |
EC Recent Not sign. diff.: |
AO: Findings reveal dysregulation of salivary immune profiles toward a TH1 phenotype in emerging adult EC users and short-term immune function may be dysregulated in young adult EC users. ARO: No pure EC users of NU (almost multi-product users). |
ARO: |
L: Small groups, no ‘pure’ product use; probably very short time of product use (< 30 d). G: No data to evaluate role of |
|
? | |||||||
K |
Cross-sectional |
• 6 Vapers (EC), EC use since ≥ 6 months • 6 Smokers (CC), CC since ≥ 6 months • 6 WP smokers, WP since ≥ 6 months • 6 Dual CC/WP smokers • 6 NU Age range (all groups) 18–65 y |
|
AO: lncRNAs allow risk estimates for COPD, asthma, IPF. ARO: No verification of EC only use. |
ARO: |
L: Small group sizes; no verification of product compliance (especially EC). G: No N-free EC group. |
|
? | |||||||
S |
Cross-sectional |
• 22 Vapers (EC), 35.5 y • 26 Smokers (CC), 32.8 y • 12 WP smokers, 32.8 y • 10 Dual CC/WP smokers, 35.5 y • 26 NU, 33.9 y |
The 4 user groups show common differential expression of micro-RNAs which are different from NU. |
AO: The exosomes/microRNAs are BMs to understand the lung injury caused by smoking and vaping. |
AO: Suggest that the differences between the user groups and NU demonstrate “nicotine-specific” effects. ARO: Given the study design, the role of |
L: Small group sizes; no verification of product compliance. G: No N-free EC group. |
|
? | |||||||
C |
Cross-over |
30 EC users (former CC, EC since 38 months), 38 y, randomly allocated to 3 conditions, separated by 7 d): • (1) EC with • (2) EC without • (3) Cessation (EC stop), 5 d |
Sign. diff. between conditions: • PG in serum: 1 ≈ 2 > 3 • PG in urine: 1 ≈ 2 > 3 • • • • • • Serum • |
AO: Short-term EC cessation can lead to decrease in lung inflammation (indicated by change in CC16). Effects appear to be related to a disturbance of the lung gas exchange. |
ARO: |
L: Only acute effects in a limited population were investigated. P: Investigations of long-term EC use (with and without |
|
0 | |||||||
|
|||||||
1 | |||||||
P |
Longitudinal (60 months) |
• 19 Smokers with COPD, switched to EC, 65 y, 22.1 cig/d at BL • 20 Smokers with COPD (control), continued CC use, 65.9 y, 20.2 cig/d at BL |
BL, and follow-up (FU) at 12, 24, 48 and 60 months • CC group: CPD almost unchanged at 20 cig/d; no sign. change or slight improvement in • EC group: decrease in CPD (20 to 1.5 cig/d); sign. improvements in lung function and walk distance, COPD exacerbations, CAT score Also improvements in dual users (about 3 cig/d) |
AO: EC use ameliorates COPD outcomes and might also reverse the harm of some smoking effects. ARO: Although dual use was evaluated separately, compliance is an open question. |
The authors speculate that ARO: From the study data, the role of |
L: Small group sizes. P: A larger study over longer time periods including a N-free EC group would be of value. |
|
0/? | |||||||
Of note: |
|||||||
J |
Cross-sectional |
• Cohort 1: 26 NU, 22 vapers (EC) • Cohort 2: 25 NU, 26 CC, 12 Waterpipe (WP), 10 Dual (CC/WP) Grouping according to self-reports |
Self-reported • EC and CC reported the most symptoms |
AO: Our pilot study showed that users have a preference toward fruit and more sweet flavors and that EC and dual use resulted in an augmented systemic immune response. ARO: Only self-reported data (except IgE and IgG). No verification of product use (particularly EC only). |
ARO: Role of |
L: Small group sizes; probably too short product use durations. G: No N-free EC group. |
|
? | |||||||
K |
Cross-over |
25 healthy and 25 asthmatic smokers (aged 40 y) vaped 1 EC (with nicotine) |
Acute changes (after Healthy subjects: • • • All BM sign changed in asthmatics after 1 EC |
AO: EC vaping resulted in acute alteration of both pulmonary function and airway inflammation in stable moderate asthmatic patients. |
The authors cite evidence that EC use without ARO: |
L: Small group sizes; only acute effects. G: No N-free EC group; no long-term observations. P: A study without these weaknesses would be of interest. |
|
0.5 / ? | |||||||
L |
Cross-over |
Evaluation of RNA expression data sets from: • Smokers (CC) • Vapers (EC with • Vapers (EC without |
• ACE2: upreg. in CC • • |
AO: CC and EC (with ARO: Product use not well characterized |
Authors do not clearly separate effects of ARO: |
L: Product use not well characterized, misclassification possible |
|
0.5 / ? | |||||||
S |
Cross-sectional |
64 Healthy, young adults, mean age: 26 y • 28 NU, PG in urine: 2.1 mg/L • 13 Vapers (EC for > 1 y, no CCs for > 5 month), PG in urine: 25.5 mg/L • 27 Smokers (CC), PG in urine: 6.6 mg/L |
• NU: 18% • EC: 54% • CC: 96% |
AO: LLM are related to EVALI, relation to inflammation is open. ARO: Dual use cannot be excluded |
ARO: |
L: Small group sizes; dual use in EC group is possible; not clear what LLM indicates. G: No N-free EC group. |
|
? | |||||||
P |
RCT |
186 Smokers (CC), African Americans/Latinx: 92/94, 43.3 y, 12.1 cig/d; randomized to • 125 EC use, 5% • 61 Controls (CC use as usual) |
Sign. changes EC • NNAL • COex No sign. changes EC • Cotinine in urine • • • • • Significances similar in EC only users |
AO: ECs may be an inclusive (suitable) harm reduction strategy for this population. ARO: 58–68% in EC group were dual users, 4% were CC only users in EC group. Compliance was not enforced. |
ARO: All EC contained 5% |
L: Only short- to medium-term study (6 weeks). G: No N-free EC group. P: Long-term study (> 1 year) including an N-free EC group would be of interest. |
|
? | |||||||
K |
Cross-sectional (acute and chronic (BL)) |
• 9 Vapers (EC since > 1 y), 23 y, range EC use: 1.5–4 y, 3.3 pack-year equivalents • 7 NU, 21 y |
Sign. diff. at BL: • • • VA/Q mismatch: EC > NU BL • No sign. diff. at BL: • SPO2 (oxygen saturation) • HR (but sign. increase after acute vaping) |
AO: EC use leads to early lung changes. Authors could not exclude some dual use. The authors suppose that nicotine is involved in the VA/Q changes. |
ARO: No direct involvement of |
L: Very small groups, dual use cannot be excluded. G: No N-free EC group. P: Larger, long-term study with N-free EC group would be of interest. |
|
?/1 | |||||||
M |
Cross-sectional (acute resp. changes) |
• 76 Vapers (EC), 20 min EC use with 5% • 73 NU, passively exposed to EC for 20 min |
Sign. changes after 20 min (active) vaping: • • • • Passive exposure: • oral temp, ↑ |
AO: Vaping with mint-flavored ECs with 5% |
ARO: |
L: Only short-term effects. |
|
? | |||||||
R |
Cross-over study (BL and 3 months investigations) |
• 60 Smokers (CC), 39.1 y, reduced CC and increased EC use (still 25% CC use after 3 months) • 20 Smokers (CC), 44.2 y; stopped CC use |
Changes after 3 months: • • • No sign. diff. in the changes between both groups |
AO: Whether the decrease in BHR observed after 3 months is maintained when using ECs over longer time periods or has an individual prognostic value, must be clarified in long-term studies. ARO: No clear improvements by EC use or stopping smoking were observed. Both groups contain CC users after 3 months. |
ARO: Role of |
L: Use of CCs in both groups. G: No N-free EC group. |
|
? | |||||||
C |
13 Cross-sectional studies (meta-analysis) |
1,039,203 Subjects • Current EC users • Ever EC users • NU Duration of EC use: < 10 y (estimate) |
Pooled OR (CI) for • Current EC: 1.36 (1.21–1.52) • Ever EC: 1.24 (1.13–1.36) |
AO: EC use is correlated with asthma (however, limitations are considered). |
ARO: |
L: All weaknesses of cross-sectional studies: temporality, misclassifications by self-reports. |
|
? | |||||||
X |
11 Cross-sectional studies (meta-analysis) |
Groups: • EC ever • EC current • EC former • Dual • CC • NU Duration of EC use: < 10 y (estimate) |
OR (CI) for • EC ever: 1.27 (1.17–1.37) • EC current: 1.30 (1.17–1.45) • EC former: 1.22 (1.08–1.39) • Dual: 1.47 (1.13–1.91) • CC current: 1.33 (1.19–1.49) |
AO: Current and former EC use is associated with asthma. ARO: Usual weaknesses of cross-sectional studies. |
ARO: Cannot be deduced from this study. |
L: Cross-sectional study: no causality, temporality open; mis-report of product use possible. G: No N-free EC group. |
|
? |
Author, year, country (Ref) | Study type | User groups / duration of product use | Endpoints and findings | Comments (bias, compliance, etc.) | Conclusions regarding nicotine's ( |
Limitations (L) / Gaps (G) / Proposals (P) |
---|---|---|---|---|---|---|
M |
Single (acute) vaping | 64 Subjects, 21 y (CC/EC history not reported, EC-naive); measurements pre and post vaping: 0.05 mL e-liquid (10 puffs), 8 mg N/mL |
AO: More frequent and higher EC use is required, experienced EC users should be used. |
The authors speculate that little or no ARO: |
L: Small sample size, EC-naive subjects, only young people, only acute effects. G: N-uptake completely unknown. |
|
? | ||||||
M |
Cross-sectional |
• 21 Male vapers (~23 y), EC use: ≥1 y, 3 mL/d, quit of occasional CC use • 21 Male NU (~23 y) |
Effects increase with EC voltage (3.0–5.9 V). |
AO: Vaping leads to moderate to severe impairment of OSH. ARO: No verification of EC only use (probably dual users included). |
Authors suggest that irritating compounds may be responsible for the observed effects. ARO: |
L: Small group sizes, only young subjects, only short duration of EC use, probably dual users included. |
? | ||||||
K |
Cross-sectional |
• 21 Male vapers (EC), 28.8 y, ECs (3 mg N/mL) since > 3 y • 21 Male NU, 28.8 y |
|
AO: EC use enlarges FAZ and decreases vascular density in retina micro-circulation. ARO: Possible dual use not mentioned. |
The authors cite evidence that ARO: The study data cannot provide involvement of |
L: Small group sizes, only young males; EC use relatively short. G: No check of dual use; no N-free EC group. |
0.5 / ? | ||||||
M |
Cross-over |
47 Dual users (daily CC (duration: 6 y), at least once per week EC use, 25 y, EC mean duration: 2.4 y, allocated to 4 conditions: • 1. CC: 1 cig, 10 puffs in 5 min • 2. EC, 10 puffs in 5 min, 18 mg N/mL • 3. EC, 10 puffs in 5 min + 25 min • 4. Sham, 60 min |
No sign. changes in |
AO: CC and EC use does not result in acute changes in central foveal (CFT) and choroid thickness (CT) in young subjects. |
ARO: No effects observed, therefore |
L: Low number of subjects, only young subjects, only short- no long-term effects were studied. G: No N-free EC group. P: A larger study, including an N-free group looking for long-term effects would be of interest. |
0 (acute effects) / ? | ||||||
A |
Cross-sectional |
NHANES 2017–2018, 5,569 subjects: • 4,519 NU, 54.3 y • 1,050 Ever EC users (EEC), 56.1 y • 463 CC (no EC) users • 143 Dual users Duration of EC use: < 10 y (estimate) |
Adjusted prevalence ratio, PR (CI) • EEC: 1.46 (1.12–1.89) • CC: 1.63 (1.18–2.25) • Dual: 2.41 (1.28–4.55) |
AO: EC use can be detrimental to bone health. ARO: Data rely on self-reports. |
The authors discuss a possible involvement of ARO: |
L: All data rely on self-reports; EC use not well characterized; subjects may have started EC use after the bone fracture. G: No N-free EC group. |
? | ||||||
T |
Cross-sectional |
Behavior and Risk Factor Surveillance System (BRFSS), 924,882 participants • 30,569 Current EC users (cEC) • 119,309 Former EC users (fEC) • 775,004 Never EC users (nEC) • 486,015 Never EC, never CC (NU)+ +: contain 29.7% former CC and 7.6% current CC (!?) Duration of EC use: < 10 y (estim.) |
Adjusted OR (*=sign) for • fEC • cEC • fEC • cEC |
AO: EC use is an important risk factor for arthritis. ARO: Usual issues with cross-sectional studies: causality/temporality, recall bias, misreports. Unclear NU group! |
The authors cite evidence that ARO: A role of |
L: Weaknesses of a cross-sectional study; no classification of the arthritis type. G: No N-free EC group. |
0.5 / ? | ||||||
B |
Cross-sectional |
151 Healthy males: • 68 NU, 44 y • 50 SLT, 45 y, 25 y SLT use (median) • 48 CC, 48 y, 28 y CC use (median) |
Sign. diff. of CC • • • • No sign. diff. between SLT and NU |
AO: Long-term use of SLT does not sign. influence exercise capacity in healthy, young subjects. |
The authors cite some evidence for negative effects of ARO: The study suggest that |
L: Small group sizes; only rel. young and well trained subjects included. P: Long-term study including more NGPs and older subjects would be of interest. |
0 | ||||||
L |
Cross-sectional |
Web-based survey with 62,276 students: • 53,466 NU • 4,508 Smokers (CC only) • 660 Vapers (EC only) • 3,642 Dual users Duration of EC use: < 10 y (estimate) |
Prevalence of • Sign. increased |
AO: Claim an urgent need for cessation programs. ARO: Misclassification of product use cannot be excluded. |
The authors cite evidence that |
L: Data rely on self-reports; misclassification possible. G: No N-free EC group. P: A study including a N-free EC group would be of interest. |
0.5–1 | ||||||
P |
Cross-sectional |
Self-reports in a Community Health Survey with 53,050 subjects from 2015/2016, mean age 45 y: • Smokers (CC, no EC) • Dual (CC and EC) • EC users • NU Duration of EC use: < 10 y (estimate) |
• • • • EC use is associated with adverse MHS, particularly in women (but no sign. diff.). |
AO: EC use is associated with adverse MHS, particularly in non-smokers and women. ARO: General problem of self-reports and bi-directionality in cross-sectional studies. |
The authors cite evidence that ARO: Study data do not allow to identify a role of |
L: Misclassification of product use and symptoms; bi-directionality in cross-sectional studies. G: No N-free EC group. |
0.5 / ? | ||||||
M |
Clinical trial |
Meta-analysis of 31 studies with 978 subjects (non-smokers) allocated to: • Nicotine patch • Placebo patch |
• • Attention* • *statistically sign. |
AO: |
ARO: Observed effects are causally related to |
L: Only acute effects; only non-smokers investigated; authors list 8 additional shortcomings. P: Study with long-term NGP users would be of interest. |
1 |
Author, year, country (Ref) | Study type | User groups / duration of product use | Endpoints and findings | Comments (bias, compliance, etc.) | Conclusions regarding nicotine's (N) role | Limitations (L) / Gaps (G) / Proposals (P) |
---|---|---|---|---|---|---|
C |
Cross-sectional |
248 Pregnant women, 232 with singleton life-birth: • 17 Dual EC/CC users • 6 Current EC only users • 23 Any current EC users • 56 Current CC users • 97 NU |
• Dual EC: 2.5 (0.7–8.8) • Current EC only: 5.1 (1.2–22.2) • Any current EC: 3.8 (1.3–11.2) • Current CC: 2.6 (0.9–7.2) |
AO: Suggest that EC use is associated with an increased risk of SGA. ARO: Strange results! Misclassification is likely. |
The authors cite (weak) evidence that ARO: |
L: Very small groups; misclassification is likely. |
? | ||||||
H |
Cross-sectional |
2,008 Men, median age: 19 y, were asked for their smoking habits (multiple use possible): • 52% CC users • 13% EC users (mostly with N) • 25% snuff users • 33% marijuana users |
Sign. diff. • Total • • Higher in daily CC |
AO: Stated that ‘confounding by behavioral factors cannot be excluded’. ARO: There is probable significant dual use in EC group. |
The authors cited evidence that EC effects were dependent and independent of ARO: |
L: Dual use (CC/EC) highly likely. G: No N-free EC group. |
? | ||||||
M |
Cross-sectional |
Pregnancy outcome in a clinic: • 218 EC users, 31 y • 195 Dual users, 29 y • 99 Smokers (CC), 29 y • 108 NU, 33 y |
Mean • EC: 3,470 • Dual: 3,140* • CC: 3,166* • NU: 3,471 * sign. lower than NU and EC |
AO: Birthweight of EC users is similar to NU. ARO: Product use relies on self-reports at 2nd trimester. |
The authors cite evidence that ARO: No effect of EC and, therefore, also of |
L: Product use at delivery not assessed; socioeconomic status higher in NU and EC. |
0 | ||||||
H |
Cross-sectional |
4,586 Women, 21–45 y, web-based study, question on current, former, never use of ECs and CCs |
|
AO: Stated that FR estimates were inconsistent and imprecise because lack of independence of CC use. |
ARO: N-free EC users were excluded. N's role cannot be deduced. |
L: No clear user groups defined. G: No N-free EC group included. |
? | ||||||
R |
Cross-sectional |
Pregnancy monitoring study (PRAMS), 79,176 women, 72,256 using no CC during pregnancy: • 241 EC before preg. (EC1) • 73 EC during preg. (EC2) • 9,795 NU (no EC, no CC) |
• EC1: no adv. effects • EC2: sign. increased prevalence in |
AO: Daily use of EC during pregnancy leads to adverse outcome. ARO: Product use relies on self-report. |
The authors cite evidence that ARO: |
L: Small EC groups; dual use in EC groups possible; heterogeneity in ECs; recall bias; false report of product use. G: No N-free EC group. P: A study including an N-free EC would be of interest (also other weaknesses avoided). |
? |
Diseases / disorder / detrimental changes | Number of evaluations | Class I (%) | Class II (%) | Class III (%) |
---|---|---|---|---|
Myocardial infarction (MI) | 7 | 28.5 | 28.5 | 43 |
Stroke | 5 | 20 | 40 | 40 |
Atherosclerosis (related diseases) | 8 | 25 | 50 | 25 |
Arterial stiffness | 19 | 21 | 32 | 47 |
Hypertension (HT) | 4 | 0 | 0 | 100 |
Heart rate (HR) / blood pressure (BP) | 18 | 0 | 28 | 72 |
CVD related BOBEs | 14 | 21 | 50 | 29 |
Sum of CVD | 75 | 16 | 35 | 49 |
Cancer (various organs or all) | 10 | 40 | 50 | 10 |
Respiratory disorders (RD) | 43 | 16 | 65 | 19 |
Oral health disorders | 23 | 9 | 57 | 35 |
Inflammation / oxidative stress | 11 | 18 | 82 | 0 |
Metabolic syndrome | 7 | 14 | 43 | 43 |
Reproduction | 5 | 20 | 80 | 0 |
Eye disorders | 4 | 20 | 50 | 20 |
Bone disorders | 2 | 0 | 50 | 50 |
Physical performance | 1 | 100 | 0 | 0 |
Mental disorders | 2 | 0 | 0 | 100 |
Author, year, country (Ref) | Study type | User groups / duration of product use | Endpoints and findings | Comments (bias, compliance, etc.) | Conclusions regarding nicotine's ( |
Limitations (L) / Gaps (G) / Proposals (P) |
---|---|---|---|---|---|---|
E |
Cross-sectional |
• 18 NU, male, 24.4 y • 21 Snuff users, male, 24.1 y, duration of snuff use: 7.0 y • 19 Smokers (CC), male, 25.3 y, duration of CC: 9.1 y |
Sign. diff. in CVD-related BOBEs (≈ : not sign): • • • • • • Not sign. diff. between groups: |
AO: Snuff use has similar but lower effects on CVD-related BOBEs, except for lipids. ARO: Use of snuff only not verified. |
The authors cite evidence that NG use does not affect lipids and that CC-related hyperlipidemia is not due to ARO: |
L: Small group sizes; only very young men included. G: Other NGPs (EC, HTP), N-free EC. P: Larger study with older subjects, including additional NGPs would be of interest. |
? | ||||||
E |
Cross-sectional |
• 20 Males, nicotine gum (NG) users (> 11 months, mean: 50 months), 48.8 y • 20 NU, 51.0 y |
Sign. diff. NG • • • • |
AO: |
ARO: |
L: Small group sizes. P: Other NGPs should be used in long-term studies (> 1 year) with these endpoints. |
0.5–1 | ||||||
O |
Cross-sectional (NHANES: 2013–2016) |
3,415 Subjects: • 2,636 NU • 30 Vapers (EC) • 711 Smokers (CC) • 38 Dual users Similar age and sex distributions Duration of EC use: < 10 y (estimate) |
No sign. diff. between groups: • • CC and dual group tend to have higher insulin resistance. Also no sign. diff. in a 12-week mice study exposed to air, CC, EC (with and without |
AO: EC use is not linked to insulin resistance. ARO: The authors concede that the EC use was not well characterized (confounding possible). |
Authors cite evidence that ARO: Data suggest that EC and |
L: Small EC and dual group sizes; no verification of EC only status; too short EC use? G: No N-free EC group. |
0 / ? | ||||||
K |
Cross-sectional |
All men: • 337 Dual users (CC+EC), 36.7 y, CotU: 1,303 ng/ml, 15.1 cig/d • 4,079 CC only, 46.3 y, CotU: 1,236 ng/ml, 14.8 cig/d • 3,027 Never smokers (NS), 39.8 y, CotU: 0.7 ng/ml |
Sign. diff. of dual users to other groups: • • • • • • |
ARO: Proportion of EC use in dual users appears low. |
ARO: Role of |
L: EC only group is missing. |
? | ||||||
A |
Cross-over |
11 Smokers (CC), healthy, middle-aged were investigated at 3 timepoints: • 1. Prior to CC cessation with NRT • 2. After 6 weeks with NRT (N patch) • 3. After further 2 weeks with no CC and no NRT |
• • |
AO: |
ARO: |
L: Very small group sizes; short phases with G: No NGPs studied (including EC with/without P: Larger long-term study with the mentioned groups would be of interest. |
0 / ? | ||||||
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1 | ||||||
C |
Prospective (5 pooled cohort studies) |
54,531 Never-smoking men, mean age 49 y, among them never and current snus users mean FU: 10.3 y Duration of snus use: 10–30 y (estimate) |
Harm ratio (CI) for • • (boxes/week) • use (<30 |
AO: High consumption. of snus is a risk factor for DT2, as is use of CC. ARO: Use of snus only not verified. |
The authors state that the results support the notion that ARO: |
L: Only self-reports on product use, no verification. P: Study including NGPs (with/without |
0.5–1.0 | ||||||
A |
Cross-sectional |
• 143,952 Never EC users • 1,339 Current EC users (EC) • 7,625 Former EC users (FEC) Duration of EC use: < 10 y (estimate) |
Self-reported • EC: 1.97 (1.25–3.10) • FEC: 1.07 (0.84–1.37) Risk was higher in males History in never EC users sign. higher than in the other 2 groups ( |
AO: EC use may be associated with prediabetes. ARO: No verification of reported EC use was performed. |
ARO: |
G: No verifications of self-reports on prediabetes and EC use. P: A long-term study with objective verifications (dual use, HbA1c, blood glucose) would be of interest. |
? |
Author, year, country (Ref) | Study type | User groups / duration of product use | Endpoints and findings | Comments (bias, compliance, etc.) | Conclusions regarding nicotine's ( |
Limitations (L) / Gaps (G) / Proposals (P) |
---|---|---|---|---|---|---|
C |
Cross-over |
10 NU (CC and EC naive), 28.7 y: Vaped an EC (without Blood samples at −30 (BL), 30 min, 1, 2, 4, 6 h |
Sign. changes of ox. stress and inflammation BMs ( • • • • BMs returned to BL after 6 h |
AO: EC use (also without N) increases ox stress and inflammation and thus vascular pathologies. |
The authors cite evidence that EC could adverse impacts also without ARO: |
L: Small sample size; only young and EC/CC-naive subjects; only acute effects. G: No group with N-containing ECs. P: A study with chronic EC users would be of interest. |
? | ||||||
S |
Cross-sectional |
• 26 NU, 33.9 y • 22 EC users (mean duration of use 2.00 ± 1.64 y), 35.5 y |
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AO: EC use is risk factor for various systemic diseases and lung injuries. |
ARO: |
L: Small group sizes; short use of ECs. G: No positive control (CC); no N-free EC group. |
M |
Cross-sectional |
• 430 Non-smokers (NS), 38.4 y • 715 CC users, 42.3 y • 63 EC users, 37.1 y |
Sign. diff. in baseline biomarker levels between groups: • • • • Not sign. diff. between groups: • |
AO: EC use may be associated with systemic inflammation as in CC users. ARO: only deducible from model calc. |
ARO: No conclusions on |
L: Small group size for EC users; EC use possibly only in last month. |
? | ||||||
O |
Cross-sectional |
• 62 Smokers (CC), 47.1 y • 132 Vapers (EC, 70 tank, 62 cartridge), 44.4 y Subjects used own brands Minimum use of EC: 6 months |
Nequ (mg/g crea): • CC: 10.1; EC: 6.3 • CC: 7.3; EC: 6.6 • CC: 56.0; EC: 55.4 • CC: 952.6; EC: 844.2 • CC: 480.9; EC: 342.7 • CC: 266.9; EC: 217.9 Model calc.: all diff. CC |
AO: EC users may have lower health risks than CC users. ARO: 6 months EC use approaches long-term use. Compliance is somewhat uncertain. |
ARO: Since Nequ are sign. lower in vapers, an influence of |
L: Larger group sizes and longer EC use would be better. G: No inclusion of N-free ECs. |
? | ||||||
S |
Cross-sectional |
• 19 NS, 23–66 y • 21 Vapers (EC only in the past 6 months, confirmed by NNAL in urine), 19–66 y • 13 Smokers (CC), 24–75 y |
BMs in urine for ox stress: • • • Sign. corr. between total metals and metallothioneine and 8-OHdG in EC users. |
AO: The biomarker levels in EC users were similar to (and not lower than) CC. In EC users, there was a link to elevated total metal exposure and oxidative DNA damage. ARO: At least mid-term use of ECs only (6 months). EC compliance not sufficiently approved. |
ARO: Role of |
L: Small groups. G: No N-free EC group. |
? | ||||||
P |
Cross-sectional |
Women in reproductive age (WRA) (18–49 y): • 74 EC users (all former smokers), CotU: 91.9 ng/mL • 536 Smokers (CC), CotU: 1,508 ng/mL • 448 NU (controls), CotU: 0.4 ng/mL |
• • |
AO: WRA who use ECs had lower levels of some of the evaluated urinary BMs of toxicant exposure and serum BMs of inflammation and oxidative stress than those who use CCs. ARO: |
ARO: A role of |
L: Small EC group size; EC use appears to be low (or only occasional); duration of EC use not provided. |
? | ||||||
S |
Cross-sectional |
PATH Wave 1 (2013–2014): • 2,191 NU • 261 EC only • 3,261 CC only • 1,417 Dual |
Ratios of BMs for ox. stress and inflamm. • • • • • Ratios • EC: < 1* (all BMs) • Dual: ~1 (not sign., all BMs) *: sign. |
AO: We observed no difference in inflammatory and oxidative stress biomarkers between exclusive EC users and NU, and levels were lower in exclusive EC users relative to exclusive CC. ARO: Results were surprisingly consistent. Same weaknesses: Danger of product misclassification. |
Authors do not discuss the role of ARO: |
L: Only short period of EC use possible; mis-report of product use possible. G: No N-free EC group. P: Study with other NGPs and N-free group would be of interest. |
? | ||||||
T |
Cross-sectional |
Study with: • 23 NU, 24.0 y, CotP: 2.5 ng/mL • 37 EC only users, 28.0 y, CotP: 115 ng/mL, 8.0 y CC, 3.0 y EC • 22 CC only users, 36.5 y, CotP: 121 ng/mL, 21.9 y CC |
|
AO: Important genes for disease development are dysregulated, with high impact on public health. ARO: Dual use possible chronic or acute effects? |
ARO: |
L: Small samples sizes; misclassification of product use not excluded. G: No N-free EC group. |
? | ||||||
K |
Cross-over |
Smokers (CC) allocated to switch to: • 8 NRT/Varenicline, no CCs, 55 y • 7 EC, no CC, 57 y • 7 continued CC, 55 y After 12 weeks inflammation BMs were analyzed in ELF (NEC) |
• NRT/Var: • EC and CC: all three BMs unchanged |
AO: Inflammation in the upper airways persisted after switching to EC. ARO: Compliance only checked by COex. |
ARO: Findings with NRT suggest that systemic |
L: Very small group sizes; compliance over 12 weeks not verified. G: No N-free EC group P: A study avoiding these weaknesses would be of interest. |
0 / ? | ||||||
L |
Cross-sectional |
PATH study Wave 1: • 2,442 Smokers (CC only) • 169 Vapers (EC only) • 970 Dual users: with increasing frequency of EC use • 1,700 NU |
BOBEs: • • • • BOBEs levels decrease with increasing EC use. |
AO: Dual users must be differentiated according to frequency of use. ARO: Same weaknesses as other PATH studies. |
ARO: Role of |
L: Certainty of self-reports for product use not reliable. G: No N-free EC group. |
? | ||||||
A |
Cross-sectional |
195 Subjects • 97 Nicotine pouch users (NP), 25.6 y, mean NP duration: 2.8 y • 30 Smokers (CC), 29.7 y, CC use for 11.4 y • 29 Former smokers (fCC), 32.5 y • 39 NU, 29.6 y, no CCs since 3.5 y |
BOBEs diff. between groups (≈ not sign.): • • • • • • |
AO: NP users have more favorable BOPH than smokers. ARO: Sampling during clinic stay, CEVal for long-term compliance. |
ARO: No effect of NP on BOBEs for ox. stress and inflammation, therefore |
L: Partly small groups; relatively short NP use. G: no other NGPs, no N-free EC group. P: A study avoiding these weaknesses would be of interest. |
0 / ? |
Limitations / weaknesses / gaps | Avoidance / improvements |
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1. Duration of NGP use in most studies was too short for the development of diseases or disorders | Inherent weakness, due to the relative short market availability of modern NPGs (ECs, HTPs, NPs). Improvement can only come with time |
2. Group sizes in most studies was too small | Larger studies have to be performed in the future |
3. Many studies included only one sex (mostly males) | Males and females should be included |
4. In many studies, the NGP users were relatively young (hence also the controls) | Inherent weakness (see 1.) |
5. The majority of studies investigated ECs (HTPs and NPs are clearly under-represented) | All NGPs should be evaluated for the health risks. With respect to NPs (and partly also to HPTs), presently this is an inherent weakness (see 1.) |
6. Concealed dual use (mostly CC + NGP) was a general problem in epidemiological and field studies. Erroneously increased risks for NGP could be the consequence | Exclusive NGP use (‘NGP only’) is preferable for a reliable product risk evaluation. To achieve this goal will be quite difficult for the years to come. The application of suitable (ideally product-specific) biomarkers which indicate concurrent CC use over weeks to months could help to circumvent this problem |
7. The long-term use history of tobacco/nicotine products in study subjects was usually not adequately assessed | More efficient questionnaires have to be developed for this purpose. Where applicable, interviewers have to be well-trained. Combining questionnaires/interviews with suitable biomarkers would be also of advantage |
8. The majority of studies did not include dose-response relationships (DRR) | An existing DRR is very strong evidence for a (causal) effect. Therefore, future NGP study designs should allow to investigate DRRs |
9. In most studies, only one control group was included | Ordinarily, NGP studies can (and should) have a positive and a negative control group: positive controls are usually smokers (or in longitudinal studies: smokers who continue to smoke); negative controls are usually (‘life-time’) non-users (NU) (or in longitudinal studies: smokers who quit smoking) |
10. Almost all (long-term) human studies do not include a nicotine-free product group (only a few short-term experimental studies do) | For elucidating the role of nicotine in disease/disorder development upon NGP use, comparison to a nicotine-free NGP would be ideal. However, it appears rather unlikely that this goal can be achieved in field studies |
11. In many studies NGP users are former smokers, there was rarely a group of initial NGP users | For a proper evaluation of the health risk of NGP use, initial NGP user would be most suitable. However, this again is an inherent weakness. Improvement (i.e. inclusion of groups of initial NGP users) would be possible in some years from now. On the other hand, the main focus of NGP evaluation is presently to approve their suitability for tobacco harm reduction. For this purpose, no initial NGP users are required. |
12. Cross-sectional and case-control studies (most frequently used in epidemiology) have immanent limitation: in principle no causality can be deduced, temporality (what is first, product use or disorder?) | In principle, prospective studies can avoid these weaknesses. However, cross sectional studies are faster and much cheaper and will, therefore, always take up an important role. More important is the careful interpretation of results from cross-sectional studies, clearly pointing to weaknesses and limitations |