Shift Work and Cancer: State of Science and Practical Consequences
In 2007, an expert Working Group convened by the IARC Monographs Programme concluded that shift work that involves circadian disruption is probably carcinogenic to humans (Group 2A). We scrutinised the epidemiological basis for this conclusion, with a focus on, but not limited to, breast and prostate cancers. We further considered practical consequences for shift workers in our industry against the background of new findings.
We carried out a literature search including the epidemiological studies cited by IARC and newer available literature on shift work and cancer.
Since the IARC assessment, eleven new studies have emerged, ten of which have already been published, with inconclusive results. Heterogeneity of exposure metrics and study outcomes and emphasis on positive but non-significant results make it difficult to draw general conclusions. Also, several reviews and commentaries, which have been published meanwhile, came to equivocal results. Published evidence is widely seen as suggestive but inconclusive for an adverse association between night work and breast cancer, and limited and inconsistent for cancers at other sites and all cancers combined.
At this point in time it can not be ruled out that shift work including night work may increase the risk for some cancers in those who perform it. However, shift schedules can be organised in ways that minimise the associated health risks, and the risks may be further reduced through the implementation of structured and sustained health promotion programs specifically tailored to the needs of shift workers.
Straif K, Baan R, Grosse Y, Secretan B, El Ghissassi F, Bouvard V, Altieri A, Benbrahim-Tallaa L, Cogliano V. Carcinogenicity of shift-work, painting, and fire-fighting. Lancet Oncol 2007;8:1065-6.
Kolstad HA. Nightshift work and risk of breast cancer and other cancers - a critical review of the epidemiologic evidence. Scand J Work Environ Health 2008;34:5-22.
World Health Organization, International Agency for Research on Cancer. Painting, Firefighting, and Shiftwork. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans Vol. 98, 2010 [displayed 30 April 2012]. Available at http://monographs.iarc.fr/ENG/Monographs/vol98/mono98.pdf
Schernhammer ES, Laden F, Speizer FE, Willett WC, Hunter DJ, Kawachi I, Colditz GA. Rotating night shifts and risk of breast cancer in women participating in the nurses' health study. J Natl Cancer Inst 2001;93:1563-8.
Schernhammer ES, Kroenke CH, Laden F, Hankinson SE. Night work and risk of breast cancer. Epidemiology 2006;17:108-11.
Schwartzbaum J, Ahlbom A, Feychting M. Cohort study of cancer risk among male and female shift workers. Scand J Work Environ Health 2007;33:336-43.
Tynes T, Hannevik M, Andersen A, Vistnes AI, Haldorsen T. Incidence of breast cancer in Norwegian female radio and telegraph operators. Cancer Causes Control 1996;7:197-204.
Hansen J. Increased breast cancer risk among women who work predominantly at night. Epidemiology 2001;12:74-7.
Lie JA, Roessink J, Kjaerheim K. Breast cancer and night work among Norwegian nurses. Cancer Caus Control 2006;17:39-44.
Davis S, Mirick DK, Stevens RG. Night shift work, light at night, and risk of breast cancer. J Natl Cancer Inst 2001;93:1557-62.
O'Leary ES, Schoenfeld ER, Stevens RG, Kabat GC, Henderson K, Grimson R, Gammon MD, Leske MC; Electromagnetic Fields and Breast Cancer on Long Island Study Group. Shift work, light at night, and breast cancer on Long Island, New York. Am J Epidemiol 2006;164:358-66.
Pukkala E, Auvinen A, Wahlberg G. Incidence of cancer among Finnish airline cabin attendants, 1967-92. BMJ 1995;311:649-52.
Lynge E. Risk of breast cancer is also increased among Danish female airline cabin attendants. BMJ. 1996;312:253.
Wartenberg D, Stapleton CP. Risk of breast cancer is also increased among retired US female airline cabin attendants. BMJ 1998;316:1902.
Haldorsen T, Reitan JB, Tveten U. Cancer incidence among Norwegian airline cabin attendants. Int J Epidemiol 2001;30:825-30.
Rafnsson V, Tulinius H, Jónasson JG, Hrafnkelsson J. Risk of breast cancer in female flight attendants: a population-based study (Iceland). Cancer Causes Control 2001;12:95-101.
Blettner M, Zeeb H, Langner I, Hammer GP, Schafft T. Mortality from cancer and other causes among airline cabin attendants in Germany, 1960-1997. Am J Epidemiol 2002;156:556-65.
Reynolds P, Cone J, Layefsky M, Goldberg DE, Hurley S. Cancer incidence in California flight attendants (United States). Cancer Causes Control 2002:13:317-24.
Linnersjö A, Hammar N, Dammström BG, Johansson M, Eliasch H. Cancer incidence in airline cabin crew: experience from Sweden. Occup Environ Med 2003;60:810-14.
Zeeb H, Blettner M, Langner I, Hammer GP, Ballard TJ, Santaquilani M, Gundestrup M, Storm H, Haldorsen T, Tveten U, Hammar N, Linnersjö A, Velonakis E, Tzonou A, Auvinen A, Pukkala E, Rafnsson V, Hrafnkelsson J. Mortality from cancer and other causes among airline cabin attendants in Europe: a collaborative cohort study in eight countries. Am J Epidemiol 2003;158:35-46.
Blettner M, Zeeb H, Auvinen A, Ballard TJ, Caldora M, Eliasch H, Gundestrup M, Haldorsen T, Hammar N, Hammer GP, Irvine D, Langner I, Paridou A, Pukkala E, Rafnsson V, Storm H, Tulinius H, Tveten U, Tzonou A. Mortality from cancer and other causes among male airline cockpit crew in Europe. Int J Cancer 2003:106:946-52.
Kubo T, Ozasa K, Mikami K, Wakai K, Fujino Y, Watanabe Y, Miki T, Nakao M, Hayashi K, Suzuki K, Mori M, Washio M, Sakauchi F, Ito Y, Yoshimura T, Tamakosh A. Prospective cohort study of the risk of prostate cancer among rotating-shift workers: findings from the Japan collaborative cohort study. Am J Epidemiol 2006;164:549-55.
Conlon M, Lightfoot N, Kreiger N. Rotating shift work and risk of prostate cancer. Epidemiology 2007;18:182-3.
Pronk A, Ji B-T, Shu X-O, Xue S, Yang G, Li H-L, Rothman N, Gao Y-T, Zheng W, Chow W-H. Night-shift work and breast cancer risk in a cohort of Chinese women. Am J Epidemiol 2010;171:953-9.
Pesch B, Harth V, Rabstein S, Baisch C, Schiffermann M, Pallapies D, Bonberg N, Heinze E, Spickenheuer A, Justenhoven C, Brauch H, Hamann U, Ko Y, Straif K, Bröing T. Night work and breast cancer - results from the German GENICA study. Scand J Work Environ Health 2010;36:134-41.
Villeneuve S, Févotte J, Anger A, Truong T, Lamkarkach F, Gaye O, Kerbrat P, Arveux P, Miglianico L, Imbernon E, Guénel P. Breast cancer risk by occupation and industry: analysis of the CECILE study, a population-based case-control study in France. Am J Ind Med 2011;54:499-509.
Hansen J, Stevens RG. Case-control study of shift-work and breast cancer risk in Danish nurses: impact of shift systems. Eur J Cancer 2011 (Epub ahead of print)
Lie JA, Kjuus H, Zienolddiny S, Haugen A, Stevens RG, Kjaerheim K. Night work and breast cancer risk among Norwegian nurses: assessment by different exposure metrics. Am J Epidemiol 2011;173:1272-9.
Kubo T, Oyama I, Nakamura T, Kunimoto M, Kadowaki K, Otomo H, Fujino Y, Fujimoto N, Matsumoto T, Matsuda S. Industry-based retrospective cohort study of the risk of prostate cancer among rotating-shift workers. Int J Urol 2011;18:206-11.
Pukkala E, Martinsen JI, Lynge E, Gunnarsdottir HK, Sparén P, Tryggvadottir L, Weiderpass E, Kjaerheim K. Occupation and cancer - follow-up of 15 million people in five Nordic countries. Acta Oncol 2009;48:646-790.
Poole EM, Schernhammer ES, Tworoger SS. Rotating night shift work and risk of ovarian cancer. Cancer Epidemiol Biomarkers Prev 2011;20:934-8.
Schernhammer ES, Razavi P, Li TY, Qureshi AA, Han J. Rotating night shifts and risk of skin cancer in the nurses' health study. J Natl Cancer Inst 2011;103:602-6.
Lahti TA, Partonen T, Kyyrönen P, Kauppinen T, Pukkala E. Night-time work predisposes to non-Hodgkin lymphoma. Int J Cancer 2008;123:2148-51.
Wang X-S, Armstrong MEG, Cairns BJ, Key TJ, Travis RC. Shift work and chronic disease: the epidemiological evidence. Occup Med 2011;61:78-9.
Pallesen S, Bjorvatn B, Mageroy N, Saksvik IB, Waage S, Moen BE. Measures to counteract the negative effects of night work. Scand J Work Environ Health 2010;36:109-120
Ott MG, Oberlinner C, Lang S, Hoffmann G, Nasterlack M, Pluto R-P, Trauth B, Messerer P, Zober A. Health and safety protection for chemical industry employees in a rotating shift system: program design and acute injury and illness experience at work. J Occup Environ Med 2009;51:221-31.
Oberlinner C, Ott MG, Nasterlack M, Yong M, Messerer P, Zober A, Lang S. Medical program for shift workers - impacts on chronic disease and mortality outcomes. Scand J Work Environ Health 2009;35:309-18.
Yong M, Nasterlack M, Pluto R-P, Elmerich K, Karl D, Knauth P. Is health, measured by work ability index, affected by 12-hour rotating shift schedules? Chronobiol Int 2010;27:1135-48.
Merrill RM, Aldana SG, Garrett J, Ross C. Effectiveness of a workplace wellness program for maintaining health and promoting healthy behaviors. J Occup Environ Med 2011;53:782-7.
Saltychev M, Laimi K, El-Metwally A, Oksanen T, Pentti J, Virtanen M, Kivimäki M, Vahtera J. Effectiveness of multidisciplinary primary prevention in decreasing the risk of work disability in a low-risk population. Scand J Work Environ Health 2012;38:27-37.
Ott MG, Yong M, Zober A, Nasterlack M, Messerer P, Pluto R-P, Lang S, Oberlinner C. Impact of an occupational health promotion program on subsequent illness and mortality experience. Int Arch Occup Environ Health 2010;83:887-94.