Long-term melatonin use is associated with a 90% higher risk of developing heart failure in individuals with chronic insomnia. This finding comes from a preliminary study presented at the American Heart Association's Scientific Sessions 2025. The research also linked melatonin use to increased hospitalizations for heart failure and a higher risk of death from any cause.
Melatonin is a hormone that regulates sleep and wake cycles. Synthetic melatonin is available as an over-the-counter supplement in many countries, including the United States. It is commonly used to address insomnia and jet lag. The study raises questions about the long-term safety of this popular sleep aid.
Researchers analyzed five years of medical records from the TriNetX Global Research Network. They focused on adults with chronic insomnia. Participants were divided into two groups: those with at least one year of documented melatonin use and those with no record of melatonin use. Individuals with prior heart failure diagnoses or who used other sleep medications were excluded.
Among adults with insomnia, those with long-term melatonin use had a 90% higher chance of developing heart failure over five years. Heart failure occurred in 4.6% of the melatonin group compared to 2.7% in the non-melatonin group. A secondary analysis showed that the melatonin group was nearly 3.5 times more likely to be hospitalized for heart failure. Deaths from any cause were also almost twice as high in the melatonin group.
Limitations of the study include its observational nature, which means it cannot establish a direct cause-and-effect relationship. Melatonin is regulated differently across countries; some require prescriptions while others allow over-the-counter sales. This difference complicates the tracking of actual melatonin use. The study also lacked information on insomnia severity or other psychiatric disorders, which could influence both melatonin use and cardiovascular risk.
Despite these limitations, the study suggests that melatonin supplements may not be as harmless as often assumed. Further research is needed to confirm these findings and assess the cardiovascular safety of long-term melatonin use.
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