A preliminary study set to be presented at the American Heart Association’s Scientific Sessions 2025 says that the long-term use of melatonin supplements is connected to a higher risk of heart failure diagnosis, heart failure hospitalization, and death from any cause in chronic insomnia.
Melatonin, often used to support sleep and overcome insomnia, is a hormone that the body naturally processes in the pineal gland. It helps regulate the body’s sleep-wake cycle, with melatonin levels rising during darkness and falling during the day. The supplements are widely available over the counter, with no regulation in the United States, resulting in varying levels of strength and purity among different brands.
The study divided individuals into two groups: those who used melatonin long-term, defined as a year or more, and those who had no documented use of melatonin in their medical records.
“Melatonin supplements may not be as harmless as commonly assumed. If our study is confirmed, this could affect how doctors counsel patients about sleep aids,” said Ekenedilichukwu Nnadi, M.D., lead author of the study and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn, New York, per a press release from the American Heart Association.
According to the findings, adults with insomnia whose electronic health records indicated long-term melatonin use had a roughly 90% higher chance of incident heart failure over five years compared with non-users.
The researchers also discovered that the melatonin group was nearly 3.5 times more likely to be hospitalized for heart failure and nearly twice as likely to succumb to any cause compared to those in the non-melatonin group.
“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, even after balancing for many other risk factors,” Nnadi said.