A study presented at the American Heart Association’s 2025 Scientific Sessions has linked long-term use of melatonin supplements to a higher risk of heart failure in people with insomnia. Researchers reviewed five years of health records for more than 130,000 adults who had been diagnosed with insomnia and had taken melatonin for at least a year. They compared their cardiovascular outcomes with those of people who did not take the supplement.
The results showed that about 4.6% of those who used melatonin long-term developed heart failure, compared with 2.7% of non-users – a nearly 90% higher risk. Long-term users were also more than three times as likely to be hospitalized for heart failure (19% vs. 6.6%). Over the five-year period, nearly twice as many melatonin users died from any cause (7.8% vs. 4.3%).
“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,” said lead author Ekenedilichukwu Nnadi, M.D., in a statement. The researchers stressed that the findings show an association, not proof of causation, but noted the consistency of the results gives reason for caution.
The study has limitations. Chronic insomnia itself is independently 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 supplement use could be a marker of poor sleep health rather than the direct cause of heart issues. Additionally, the study identified melatonin users based on prescription records. Since melatonin is available over the counter in the United States, some regular users may have been misclassified as non-users, which could affect the comparison.
Experts have long warned about unknown safety effects of long-term melatonin use. Short-term, appropriately dosed use for occasional jet lag may be safe, but nightly long-term use is not recommended. For those looking for alternatives, improving sleep hygiene – such as avoiding late-night alcohol, keeping the bedroom dark and cool, and reducing screen time – is a good start. Another option is magnesium, an essential mineral that many people lack. Magnesium can help activate GABA receptors in the brain, which quiet an overactive nervous system and promote calm, helping with falling and staying asleep. The article noted that magnesium-based supplements are often recommended as a safer sleep aid.
The takeaway is that while this study is preliminary, it suggests that long-term nightly use of melatonin may carry more risks than previously thought. Short-term use, good sleep habits, and nutrients like magnesium remain safer ways to improve sleep naturally.
