DALLAS — A supplement some turn to for help getting some shut-eye may not be as harmless as once thought, a preliminary study suggests.
The study claims that long-term use of melatonin supplements is linked to a higher risk of heart failure, hospitalization and death in chronic insomnia patients.
The main findings indicated that long-term melatonin users had about a 90% higher chance of developing heart failure over five years compared to non-users.
A secondary analysis revealed that participants taking melatonin were nearly 3.5 times more likely to be hospitalized for heart failure and nearly twice as likely to die from any cause compared to those not taking melatonin.
The study, which has not yet been peer-reviewed, involved reviewing five years of electronic health records for more than 130,000 adults with chronic insomnia, comparing those who had used melatonin long-term with those who had never recorded its use.
Researchers found that adults with chronic insomnia who used melatonin for more than a year had a significantly higher chance of developing heart failure compared to those who did not use the supplement.
Heart failure, which happens when the heart cannot pump enough oxygen-rich blood to the body’s organ, is a common condition that affects 6.7 million adults in the U.S.
“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 Dr. Ekenedilichukwu Nnadi, the study’s lead author and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn, New York.
Melatonin is a hormone produced by the pineal gland that regulates the sleep-wake cycle, and synthetic versions are commonly used to treat insomnia and jet lag. However, the long-term cardiovascular safety of these supplements has not been well-documented.
The study‘s limitations include the lack of data on over-the-counter melatonin use in countries like the U.S., where it is available without a prescription. In the United Kingdom, melatonin requires a prescription.
The study will be presented at the American Heart Association’s Scientific Sessions 2025 in New Orleans from Nov. 7-10.
Dr. Marie-Pierre St-Onge, who was not involved in the study, noted the surprising nature of these findings given the common perception of melatonin as a safe, natural sleep aid.
”I’m surprised that physicians would prescribe melatonin for insomnia and have patients use it for more than 365 days, since melatonin, at least in the U.S., is not indicated for the treatment of insomnia. In the U.S., melatonin can be taken as an over-the-counter supplement and people should be aware that it should not be taken chronically without a proper indication,” St-Onge said.
The researchers also noted that the study could not establish a direct cause-and-effect relationship between melatonin use and heart failure.
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