Long-term melatonin use linked to 90% higher heart failure risk
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- Researchers from SUNY Downstate presented preliminary findings at the American Heart Association's Scientific Sessions 2025 linking long-term melatonin use (12+ months) to a roughly 90% higher heart failure risk over five years among 130,828 adults with chronic insomnia.
- In the analysis heart failure was diagnosed in 4.6% of the melatonin group versus 2.7% in matched non-users, while heart-failure hospitalization reached 19.0% versus 6.6% and all-cause death reached 7.8% versus 4.3%.
- A sensitivity analysis restricted to participants who filled at least two melatonin prescriptions at least 90 days apart still showed an 82% higher heart failure risk, strengthening the durability of the association.
- Lead author Ekenedilichukwu Nnadi, M.D. said the findings don't prove causation but warned melatonin supplements "may not be as harmless as commonly assumed" and could change how doctors counsel patients about sleep aids.
- Marie-Pierre St-Onge, Ph.D., chair of the AHA's 2025 sleep-health scientific statement writing group, said she was surprised physicians would prescribe melatonin for insomnia for more than 365 days, since it is not indicated for that use in the U.S.
- The study carries major limitations: because U.S. melatonin is sold over the counter, OTC users were invisible to medical records and may have been misclassified as non-users, and researchers had no data on insomnia severity or psychiatric comorbidities that could independently drive cardiovascular risk.
Why it matters: For the millions of Americans who treat melatonin as a benign sleep aid, this preliminary signal — 90% higher heart failure incidence, nearly 3.5x higher hospitalization, and roughly doubled all-cause death — could pressure physicians and regulators to revisit counseling on chronic insomnia, even as the authors stress causation is unproven and OTC misclassification muddies the data.
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