Gender differences in the association between melatonin secretion and diabetes in elderly: The HEIJO-KYO cohort.

OBJECTIVE: Reportedly, melatonin protects the pancreatic islets and decreases insulin resistance; thus, it may contribute to preventing diabetes. Epidemiological data suggested that lower melatonin secretion is associated with higher incidence of diabetes in female nurses. Such associations are unknown in the general population. We evaluated the association between melatonin secretion and diabetes in a general population, including both genders.

DESIGN: Cross-sectional study.

PARTICIPANTS: A total of 1096 community-based elderly males (n = 519) and females (n = 577) (mean age, 71.8 years) were enrolled.

MEASUREMENTS: Overnight urinary 6-sulfatoxymelatonin excretion (UME) and diabetes prevalence were measured.

RESULTS: The median UME was 6.7 μg (interquartile range, 4.0-10.5); the prevalence of diabetes was 17.5% in males and 10.7% in females. The prevalence of diabetes decreased with increasing UME quartiles among males (P for trend = 0.009) but not among females (P for trend = 0.96). In a multivariable logistic regression analysis adjusting for potential confounding factors, such as age, smoking and drinking habits, economic status, caloric intake, and physical activity, the odds ratio (OR) for diabetes was significantly lower in the highest UME quartile group compared with the lowest quartile group among males (OR, 0.35; 95% CI, 0.17-0.70; P = 0.003) but not females (OR, 0.94; 95% CI, 0.45-1.95; P = 0.87). Consistent results were observed in the analysis after adjusting for clinical parameters or using continuous UME data.

CONCLUSIONS: Melatonin secretion was significantly and inversely associated with diabetes in males but not in females. This association was independent of several important confounding factors.