A new study presented at the American Heart Association’s 2025 Scientific Sessions has linked long-term use of the sleep supplement melatonin to a higher risk of heart failure. The research looked at health records from more than 130,000 adults diagnosed with insomnia who had taken melatonin for at least a year and compared their cardiovascular outcomes to those of people who did not take the supplement.
About the study
Researchers reviewed five years of medical data to examine the connection between melatonin use and heart disease. The study included only people with a formal diagnosis of insomnia. The findings were striking: about 4.6% of long-term melatonin users developed heart failure, compared to 2.7% of non-users. That represents a nearly 90% higher risk. Additionally, 19% of melatonin users were hospitalized for heart failure during the study period, versus 6.6% of those who did not take the supplement. The overall death rate from any cause over five years was also higher among melatonin users: 7.8% compared to 4.3%.
Lead author Ekenedilichukwu Nnadi, M.D., said in a statement that the results were consistent and significant even after adjusting for many other risk factors. He noted that melatonin supplements are widely considered safe and natural, making the findings particularly surprising.
What the findings mean
The researchers stressed that the study shows an association, not proof of causation. Still, the strength of the link gives reason for caution. Chronic insomnia itself is already linked to a higher risk of heart problems. People who rely on melatonin for more than a year may have more severe sleep disruptions, and the supplement use could be a marker of overall poor sleep health rather than a direct cause of heart failure.
Another nuance involves how melatonin users were identified. The study relied on prescription records, which means that in the United States, where melatonin is sold over the counter, many regular users may have been misclassified as non-users. That could make the real difference between the groups harder to determine.
Safer alternatives for better sleep
Experts have long warned about the unknown long-term safety of melatonin, and this study reinforces that concern. Short-term melatonin use, such as for jet lag, may still be acceptable. But nightly long-term use is not recommended. The authors point to other options for improving sleep, starting with good sleep hygiene: avoiding alcohol late in the evening, keeping the bedroom dark and cool, and reducing screen time before bed.
For those seeking a supplement, magnesium is a widely available and well-studied alternative. About 43% of Americans do not get enough magnesium from their diet. Low magnesium levels can contribute to stress, muscle tightness, and restless sleep. Taking magnesium before bed helps calm the nervous system by activating GABA receptors, which can help people fall asleep and stay asleep.
The takeaway
Although this research is preliminary, it suggests that using melatonin every night for a long period may carry more risks than previously believed. Safer approaches to improving sleep include short-term melatonin use, establishing good sleep habits, and supporting the body with nutrients such as magnesium.
