Study Links Long-Term Melatonin Use to Higher Heart Failure Risk — But Experts Urge Caution

A popular over-the-counter sleep aid is under new scrutiny after early research suggested a potential connection between long-term melatonin use and an increased risk of heart failure. According to preliminary findings to be presented at the American Heart Association’s Scientific Sessions 2025, adults who used melatonin for at least a year had a significantly higher chance of developing heart failure compared to non-users.

Early Findings Raise Red Flags

The research, based on health records from more than 130,000 adults with insomnia, found that long-term melatonin users showed a 90% higher risk of heart failure over a five-year period. The study also linked melatonin use to increased risk of hospitalization or death due to heart failure.

Lead author Dr. Ekenedilichukwu Nnadi cautioned that the results may reshape how clinicians advise patients on sleep supplements, noting that melatonin “may not be as harmless as commonly assumed.”

Experts Call for More Research

While the findings are generating attention, sleep specialists stress that the results should not drive consumers to abruptly stop using melatonin. Experts highlight that the research is observational — meaning it identifies patterns, not cause-and-effect.

They also point to limitations, including the way melatonin users were categorized. Because melatonin is widely available without a prescription, some real-world users may have been mistakenly counted as non-users, potentially affecting results. Additionally, insomnia itself — along with related conditions like anxiety and depression — may contribute to heart risks independent of melatonin use.

What’s Next

Researchers emphasize the need for further study before drawing firm conclusions. For now, healthcare providers recommend discussing sleep challenges with a medical professional, especially for those using melatonin long-term.