The long-term use of melatonin supplements, commonly taken for sleep disorders like insomnia, has been found to increase the risk of heart failure, heart failure-related hospitalization, and death. This association, revealed by a preliminary study, was presented at the American Heart Association’s Scientific Sessions 2025 in New Orleans, where the latest cardiovascular research is showcased. The findings challenge the common perception that melatonin is a harmless sleep aid.
Understanding Melatonin and Its Uses
Melatonin is a naturally occurring hormone produced by the pineal gland that regulates the sleep-wake cycle. Levels of melatonin increase in darkness and decrease in light. Synthetic melatonin supplements are widely available over the counter, often marketed as a solution for insomnia or jet lag. However, the long-term safety of these supplements, particularly regarding cardiovascular health, has not been well-established.
In the U.S., melatonin is not regulated, and the purity and strength of supplements can vary significantly from one brand to another. This lack of regulation raises concerns about the potential risks associated with extended use of melatonin for sleep support.
Study Design and Methodology
The study analyzed electronic health records from the TriNetX Global Research Network, which includes data on millions of patients worldwide. Researchers compared adults with chronic insomnia who used melatonin for at least a year (the “melatonin group”) to those with insomnia who had never used melatonin (the “non-melatonin group”). Only adults without a prior diagnosis of heart failure or those not taking other sleep medications were included in the analysis.
Key Findings of the Study
The study revealed concerning results about the relationship between melatonin use and heart failure:
- Adults with chronic insomnia who used melatonin long-term (12 months or more) had a 90% higher chance of developing heart failure compared to those who did not use melatonin (4.6% vs. 2.7%, respectively).
- When analyzing those who had at least two melatonin prescriptions filled 90 days apart, the risk of heart failure was still significantly higher (82% increase) compared to the non-melatonin group.
Hospitalization and Mortality Risks
The study also found that melatonin use was associated with an increased likelihood of hospitalization and death:
- Participants using melatonin were 3.5 times more likely to be hospitalized for heart failure (19.0% vs. 6.6%).
- Melatonin users had nearly double the risk of dying from any cause compared to those not using melatonin (7.8% vs. 4.3%).
Expert Insights and Concerns
Lead author of the study, Dr. Ekenedilichukwu Nnadi, emphasized the importance of understanding the potential risks of melatonin, a supplement often seen as benign. He highlighted that the long-term effects on heart health may not be as well-known as previously thought.
Dr. Marie-Pierre St-Onge, who was not involved in the study but serves as an expert for the American Heart Association, stressed that melatonin is not officially recommended for chronic insomnia treatment in the U.S. She also cautioned against long-term use of melatonin supplements without proper medical oversight, as they may not be as safe as marketed.
Limitations and Future Research
While the study’s findings are significant, the researchers acknowledged several limitations. The database used includes data from both prescription and over-the-counter users, which could lead to discrepancies in the results. Additionally, the study could not account for the severity of insomnia or coexisting psychiatric conditions, which may influence both melatonin use and heart health.
Dr. Nnadi concluded that more research is needed to establish a clear cause-and-effect relationship between melatonin use and heart failure risk. This would help determine whether the observed associations are truly causal and inform clinical recommendations for patients using melatonin for sleep disorders.
Study Background and Design Details
The study included 130,828 adults diagnosed with chronic insomnia, with an average age of 55.7 years. Of these, 65,414 participants had been prescribed melatonin at least once and used it for a minimum of one year. Researchers matched this group to a control group of people who had never used melatonin, taking into account 40 factors such as demographics, health conditions, and medications. The findings were based on five years of electronic health records, including heart failure diagnoses, hospitalizations, and death records.
Conclusion
These findings raise important questions about the long-term safety of melatonin supplements, particularly for individuals with chronic insomnia. As melatonin use grows in popularity, it is crucial to understand the potential risks it may pose to heart health. Clinicians and patients should weigh the benefits and risks carefully before using melatonin for extended periods.
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