Long-term melatonin use was linked to a striking increase in heart failure risk, challenging assumptions that the popular sleep aid is harmless.
People with chronic insomnia who used melatonin long term had a roughly 90% higher risk of developing heart failure over five years, according to a large preliminary study. The findings do not prove melatonin causes heart problems, but they raise new questions about the safety of taking the popular sleep supplement for extended periods.
Long-term use of melatonin, a widely used sleep supplement, was linked to a higher risk of heart failure, hospitalization for heart failure, and death from any cause among people with chronic insomnia, according to preliminary research presented at the American Heart Association’s Scientific Sessions 2025.
The findings do not prove that melatonin itself caused the increased risks. However, they raise new questions about the long-term safety of a supplement that many people view as a harmless or “natural” way to improve sleep.