Long-Term Melatonin Use Linked to Heart Failure Risk in Insomnia Study

A groundbreaking preliminary study set to be presented at the American Heart Association's Scientific Sessions 2025 reveals alarming findings about the long-term use of melatonin supplements. The research, led by Dr. Ekenedilichukwu Nnadi from SUNY Downstate/Kings County Primary Care, analyzed five years of health records for more than 130,000 adults with chronic insomnia. The findings showed that those who used melatonin for at least one year had approximately 90% higher risk of developing heart failure compared to matched non-users. The study, which examined data from the TriNetX Global Research Network, also found that melatonin users were nearly 3.5 times more likely to be hospitalized for heart failure and nearly twice as likely to die from any cause during the five-year observation period.

The research specifically focused on adults with chronic insomnia who had documented melatonin use in their electronic health records, with the melatonin group consisting of 65,414 participants who had used the supplement for at least one year. These individuals were carefully matched with non-users on 40 different factors including demographic information, existing health conditions, and medications. The study excluded people who had previously been diagnosed with heart failure or had been prescribed other sleep medications. Despite the strong associations found, researchers emphasized that the study cannot prove a cause-and-effect relationship and noted several limitations, including the fact that over-the-counter melatonin use in countries like the U.S. wouldn't be captured in prescription records.

Marie-Pierre St-Onge, Ph.D., chair of the writing group for the American Heart Association's 2025 scientific statement on sleep health, expressed surprise that physicians would prescribe melatonin for insomnia for extended periods, noting that in the U.S., melatonin isn't officially indicated for insomnia treatment and is available over-the-counter without regulation. The findings raise significant safety concerns about melatonin, which is widely marketed as a natural and safe sleep aid. Researchers caution that while the results are concerning, they represent preliminary findings that require confirmation through peer-reviewed publication and additional studies to establish whether melatonin directly contributes to cardiovascular risks.