New Delhi, Nov. 7 -- Melatonin is one of the most commonly used over-the-counter sleep supplements in the United States. Nearly six million Americans rely on it to fall asleep faster or sleep longer.

But a new study presented at the American Heart Association (AHA) Scientific Sessions 2025 warns that long-term use may carry serious risks. Adults with insomnia who took melatonin for at least a year had a much higher chance of developing heart failure, according to researchers.

Compared with similar adults who did not use melatonin, they also have a much greater chance of being hospitalized for it or dying from any cause over the next five years.

Researchers reviewed health records from more than 130,000 adults with insomnia and no histo...