A new analysis presented at the American Heart Association’s Scientific Sessions 2025 suggests that taking melatonin supplements for a year or longer may be associated with a higher risk of heart failure, more hospitalizations for heart failure, and increased all-cause mortality among people with insomnia. The results have not yet been published in a peer-reviewed journal.
What the researchers did
The team used electronic health records from the TriNetX Global Research Network covering five years and identified more than 130,000 adults with a diagnosis of insomnia (average age about 55; more than 60 percent women). They compared roughly 65,000 people who had records showing melatonin use for at least one year with about 65,000 people who had no recorded melatonin use. None of the participants had prior heart failure or prescriptions for other sleep medications.
Key findings
Compared with people who did not use melatonin, long-term melatonin users had:
– about a 90 percent higher risk of developing heart failure over five years,
– roughly 3.5 times the likelihood of being hospitalized for heart failure,
– nearly double the risk of dying from any cause during the follow-up period.
Important caveats
The investigators and outside experts emphasized that these findings show association, not causation. Several alternative explanations could account for the results, including differences in underlying health between melatonin users and nonusers. For example, people taking melatonin long term may have more severe or chronic insomnia, which itself is linked to cardiovascular risk, or there could be other unmeasured factors driving the association. The analyses come from observational electronic health records and are subject to residual confounding.
Clinical and public health context
Melatonin was developed and studied primarily for short-term use, and many melatonin products are sold over the counter without consistent regulation or medical supervision. Investigators say the safety signal is concerning enough that people who rely on melatonin for extended periods should be evaluated by a clinician or sleep specialist. If these findings are confirmed by prospective studies or randomized trials, they could change guidance on long-term melatonin use.
The broader importance of sleep
Experts also reiterated the well-established benefits of adequate sleep, which is one of the American Heart Association’s Life’s Essential 8 for cardiovascular health. Good sleep supports immune function, healthy weight and metabolism, cognition, and heart health. Chronic poor sleep raises the risk of high blood pressure, stroke, heart attack, and other conditions.
Nonmedication strategies to improve sleep
– Get bright daytime light exposure, especially in the morning
– Reduce evening blue light and limit screen time before bed
– Avoid late caffeine, alcohol, and heavy meals close to bedtime
– Exercise during the day, but avoid vigorous activity right before sleep
– Keep a consistent sleep schedule, even on weekends
– Make the bedroom dark, cool, and quiet
– Use a comfortable mattress and pillow
Bottom line
This large retrospective study raises questions about long-term melatonin use in people with insomnia but does not prove harm. People who need melatonin for more than a short period should consult a healthcare provider or sleep specialist to explore underlying causes and safer alternatives while researchers conduct further study.