Key Points:
- Long-term melatonin use is linked to a 90% higher risk of heart failure and death.
- The study was observational, so it doesn’t prove cause and effect.
- Experts advise caution and medical consultation before long-term use.
Long-term use of melatonin supplements may be associated with a higher Melatonin Heart Failure Risk, according to new research to be presented at the American Heart Association’s Scientific Sessions 2025, to be held Nov. 7–10.
In a review of medical records, researchers found that adults with chronic insomnia who took melatonin for at least one year had a 90% higher chance of developing heart failure within the next five years compared with those who did not take the supplement. Melatonin users were also more than three times as likely to be hospitalized for heart failure and twice as likely to die from any cause.
“Melatonin supplements are widely thought of as a safe and ‘natural’ option to support better sleep, so it was striking to see such consistent and significant increases in serious health outcomes,” said Dr. Ekenedilichukwu Nnadi, the study’s lead author and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn.
Study details and limitations
The analysis on Melatonin Heart Failure Risk reviewed health data from more than 130,000 adults through the TriNetX Global Research Network, an international database of electronic medical records. Participants were an average of 55 years old, and about 61% were women.
Individuals with documented melatonin use for over a year were compared with those who had no recorded use. While the findings revealed strong associations between melatonin intake and heart failure, researchers emphasized that the study was observational and could not prove cause and effect.
“While the association we found raises safety concerns about the widely used supplement, our study cannot prove a direct cause-and-effect relationship,” Nnadi said. “More research is needed to test melatonin’s safety for the heart.”
Independent experts also noted several limitations. The database included countries where melatonin requires a prescription, such as the United Kingdom, and those where it does not, like the United States. This may have caused underreporting in the control group, as over-the-counter use would not appear in medical records.
Additionally, the study did not account for the severity of insomnia or mental health conditions, both of which can influence melatonin use and cardiovascular outcomes.
Melatonin and heart health
Melatonin is a hormone produced naturally by the pineal gland in response to darkness. It helps regulate the body’s sleep-wake cycle. Supplement versions are either synthetic or derived from animal sources and are widely marketed as sleep aids.
In the United States, melatonin is sold as a dietary supplement, meaning it is not regulated by the U.S. Food and Drug Administration (FDA) with the same rigor as prescription drugs. As a result, melatonin products can vary widely in strength and may contain unlisted additives.
Although previous studies have suggested potential benefits of melatonin for heart health, including antioxidant properties, the new research raises questions about long-term use and the potential for Melatonin Heart Failure Risk. Chronic insomnia, which affects roughly 10% of the global population, is itself a risk factor for cardiovascular disease.
Insomnia and disrupted circadian rhythms have been linked with increased risks of heart attack, stroke, and heart failure. Because melatonin plays a key role in regulating these rhythms, scientists are still working to understand whether supplemental use helps or harms the heart over time.
Medical guidance and next steps
Experts recommend that individuals using melatonin discuss its use with a healthcare provider, especially if they have heart conditions or take other medications. Doctors can help determine whether insomnia stems from an underlying issue such as stress, medical conditions, or poor sleep habits, and guide patients toward safer, evidence-based treatments like cognitive behavioral therapy for insomnia.
The researchers plan to conduct further studies to confirm their findings and better understand how melatonin might affect cardiovascular health and Melatonin Heart Failure Risk. Until then, experts advise caution but not alarm.
“People should not stop using melatonin based on this one study,” Nnadi said. “But these results highlight the importance of consulting a doctor before taking supplements long-term.”
