Researchers have found that regular use of melatonin supplements is not associated with an increased risk of developing type 2 diabetes or cardiovascular disease (CVD) in adults. This conclusion comes from a comprehensive study involving three large U.S. cohorts, aimed at assessing the long-term cardiometabolic effects of melatonin supplement use. This was published in The Lancet. Diabetes & Endocrinology by Yanping Li. and colleagues.

The use of melatonin supplements has risen significantly in recent years among both children and adults in the USA. However, their long-term effects on cardiometabolic health remain uncertain. To address this gap, researchers analyzed data from the Nurses' Health Study (NHS), Health Professionals Follow-up Study (HPFS), and the Nurses' Health Study II (NHS II) to determine the association between melatonin supplement use and the incidence of type 2 diabetes and cardiovascular disease.
This study included 67,202 women from the NHS, 26,629 men from the HPFS, and 65,241 women from the NHS II. Participants were aged 25-55 years (women) and 45-75 years (men) at baseline, with no prior diagnosis of cancer, cardiovascular disease, or type 2 diabetes. The main outcomes were the incidence of cardiovascular disease and type 2 diabetes, with follow-up periods extending up to 23 years.
Melatonin supplement use was assessed via self-reported questionnaires. The researchers also conducted secondary analyses to evaluate the effects of melatonin use among participants with long-term rotating night shift work, a known risk factor for adverse cardiometabolic outcomes.
• Over the follow-up period, the prevalence of melatonin supplement use doubled, rising from less than 2% in 1998-2007 to over 4% by 2014-2015, with 4.0% usage in men and 5.3% in women.
• The study documented 16,917 incident cardiovascular disease events and 12,730 incident cases of type 2 diabetes across 2,609,068 and 2,701,830 person-years of follow-up, respectively.
• The pooled multivariable-adjusted hazard ratio for cardiovascular disease among melatonin users compared to non-users was 0.94 (95% CI 0.83–1.06, p=0.32), indicating no significant association.
• The pooled multivariable-adjusted hazard ratio for type 2 diabetes was 0.98 (95% CI 0.86–1.12, p=0.80), also showing no significant link between melatonin use and diabetes risk.
• In secondary analyses, melatonin supplement use appeared to attenuate the increased risk of cardiovascular disease associated with long-term rotating night shift work (>5 years) among female nurses (p_interaction=0.013).
The results suggest that regular melatonin supplement use is not associated with an increased risk of type 2 diabetes or cardiovascular disease. This finding provides reassurance to the growing number of individuals using melatonin supplements for sleep-related issues. Notably, the study also highlighted a potential protective effect of melatonin against the cardiometabolic risks associated with long-term shift work, particularly in women.
With up to 23 years of follow-up data from three large cohorts, this study provides strong evidence that melatonin supplement use does not increase the risk of developing type 2 diabetes or cardiovascular disease in middle-aged and older adults. Further research is warranted to explore the potential benefits of melatonin in mitigating risks associated with shift work.
Reference:
Li, Y., Huang, T., Redline, S., Willett, W. C., Manson, J. E., Schernhammer, E. S., & Hu, F. B. (2024). Use of melatonin supplements and risk of type 2 diabetes and cardiovascular diseases in the USA: insights from three prospective cohort studies. The Lancet. Diabetes & Endocrinology. https://doi.org/10.1016/s2213-8587(24)00096-2