Melatonin Concentrations and Sleep Quality in Patients with Type 2 Diabetes and Obesity

There is a close relationship between melatonin as a circadian regulator and insulin, glucagon and somatostatin production. This study aimed to describe subgroups of type 2 diabetes mellitus (T2DM) patients that may benefit from melatonin clock-targeting properties. The study involved 38 participants: 26 T2DM patients, and 12 participants without diabetes in the control group. Subjects were asked to complete the questionnaire of Pittsburgh Sleep Quality Index (PSQI). Standard biochemical venous sample testing was performed, and a sample of saliva was collected for melatonin testing. Melatonin concentration in participants without obesity (body mass index (BMI) < 30 kg/m²) was significantly higher than in obese participants: 13.2 (6.4; 23.50) pg/ml vs 5.9 (0.78; 13.1) pg/ml, p = 0.035. Subjects with BMI 30 kg/m² had a significantly higher PSQI score than non-obese subjects: 7 (4.5; 10) vs 5.5 (3; 7), p = 0.043. T2DM patients showed significantly lower levels of melatonin than the control group: 6.1 (0.78; 12.2) pg/ml vs 17.8 (8.2; 25.5) pg/ml, p = 0.003. T2DM patients using short-acting insulin analogues showed a significantly higher PSQI score than patients not using insulin: 9 (6; 10) vs 6 (3; 8), respectively (p = 0.025). Poor sleep quality was more prevalent in patients with diabetic retinopathy than in those without this complication (p = 0.031). Lower melatonin levels were detected in T2DM and obese patients. Furthermore, poor sleep quality was observed in T2DM patients using short-acting insulin analogues and those with diabetic retinopathy, and obese individuals.