New research links popular sleep supplement to increased heart failure, hospitalization and death rates among insomnia patients
Melatonin supplements may not be the harmless sleep solution millions believe them to be. A sweeping new study tracking more than 130,000 adults with insomnia has uncovered troubling connections between long-term melatonin use and serious heart problems.
The research, set to be presented at the American Heart Association’s Scientific Sessions 2025, found that people who used melatonin for at least one year faced a 90% higher chance of developing heart failure compared to those who never used the supplement. The findings also revealed nearly double the death rate among melatonin users over a five-year period.
Understanding melatonin’s widespread appeal
Melatonin has become a go-to remedy for sleep troubles across the country. The hormone, naturally produced by the brain’s pineal gland, helps regulate our sleep-wake cycles. Synthetic versions flood pharmacy shelves as over-the-counter supplements, marketed as natural and safe alternatives to prescription sleep medications.
Unlike prescription drugs, these supplements face minimal regulation in the United States. This means strength, purity and quality can vary dramatically between brands, leaving consumers largely in the dark about what they’re actually taking.
The study’s alarming discoveries
Researchers analyzed electronic health records from a massive international database, focusing on adults with chronic insomnia. They compared those who used melatonin for 12 months or longer against matched peers who never had the supplement recorded in their medical files.
The results painted a concerning picture. Among melatonin users, 4.6% developed heart failure over five years, compared to just 2.7% of non-users. When researchers examined hospitalization rates, the gap widened dramatically. Nearly one in five melatonin users required hospital care for heart failure, compared to fewer than one in fifteen non-users.
Death rates told an equally stark story. The melatonin group showed a 7.8% mortality rate over the study period, while the control group registered 4.3%.
Expert reactions and melatonin safety concerns
Dr. Ekenedilichukwu Nnadi, the study’s lead author and chief resident at SUNY Downstate/Kings County Primary Care, expressed surprise at the consistency of the negative outcomes. The findings held even after researchers accounted for numerous other risk factors that could influence heart health.
Dr. Nnadi noted that melatonin supplements may not be as harmless as commonly assumed. If the study findings are confirmed, this could significantly affect how doctors counsel patients about sleep aids.
The research has caught the attention of sleep specialists who weren’t involved in the study. Dr. Marie-Pierre St-Onge from Columbia University Irving Medical Center pointed out that melatonin isn’t actually approved for treating insomnia in the United States, making the long-term prescription patterns particularly puzzling.
Study limitations and future research needs
The research comes with important caveats. The database included countries where melatonin requires a prescription alongside nations where it’s sold over-the-counter. This created a potential blind spot, as people buying melatonin without prescriptions wouldn’t appear in medical records as users.
The study also couldn’t account for insomnia severity or the presence of depression and anxiety disorders, which might influence both melatonin use and heart disease risk. Most critically, the research shows correlation, not causation. It cannot definitively prove that melatonin directly causes heart problems.
What this means for melatonin users
While the findings raise red flags, they don’t provide final answers about melatonin’s safety profile. The study represents preliminary research that hasn’t undergone peer review, a crucial step in validating scientific findings.
However, the scope and consistency of the results warrant serious consideration. Heart failure affects 6.7 million American adults, making any factor that might increase risk a public health concern.
The research underscores the need for more rigorous studies examining melatonin’s long-term cardiovascular effects. Until then, people considering extended melatonin use might want to discuss alternatives with their healthcare providers.