Melatonin not associated with increased diabetes, cardiovascular disease risk

Researchers reviewed data from three longitudinal studies of health care professionals to parse out potential effects of self-reported melatonin use on overall health.

Melatonin supplement use was not associated with risk of type 2 diabetes or cardiovascular disease among three large prospective cohorts of middle-aged and older men and women, after 23 years of follow-up.

Researchers assessed potential associations between regular use of melatonin supplements and the risk of type 2 diabetes or cardiovascular disease in adults by combining data from the Nurses' Health studies and the Health Professionals Follow-up Study. Women ages 25 to 55 years and men ages 45 to 75 years who had no diagnosis of cancer and who responded to a yes-or-no question about melatonin use were included. Researchers excluded those with cardiovascular disease or type 2 diabetes at baseline. The main outcomes were cardiovascular disease and type 2 diabetes incidence. In secondary analyses, researchers stratified patients by duration of rotating night shift work in the Nurses' Health Study and Nurses' Health Study II to examine whether the associations with melatonin differed in this group. Results were published online May 3 by The Lancet Diabetes and Endocrinology.

For the cardiovascular disease analysis, researchers included 67,202 women from the Nurses' Health Study (follow-up from 1998 to 2019; mean age at baseline, 63.6 years), 26,629 men from the Health Professionals Follow-up Study (1998 to 2020; mean age at baseline, 62.9 years), and 65,241 women from the Nurses' Health Study II (2003 to 2019; mean age, 48.2 years). Melatonin supplement use in the study cohorts doubled from less than 2% in 1998 to 2007 to 4.0% in men and 5.3% in women in 2014 to 2015.

In a pooled analysis of the three cohorts, compared with nonusers of melatonin supplements, those who took melatonin had an insignificant difference in cardiovascular disease risk (hazard ratio [HR], 0.94 [95% CI, 0.83 to 1.06]; P=0.32) and diabetes risk (HR, 0.98 [95% CI, 0.86 to 1.12]; P=0.80). In secondary analyses, melatonin supplement use appeared to attenuate the positive association between long-term shift work of more than five years and risk of cardiovascular disease among female nurses.

The study authors wrote that more research is needed to assess whether melatonin was associated with health benefits for nurses on rotating night shift work.

An accompanying editorial noted there are crucial limitations to consider when interpreting and generalizing the study's results, including that dosing and formulation data were not recorded and that nurses using melatonin might be more health conscious in general. "Another important point worth considering is that it is still unclear regarding whether similar associations between melatonin use and cardiovascular disease would be observed among men working rotational shifts," the editorial stated.