Study Links Long-Term Melatonin Use to Higher Heart Failure Risk

Researchers Raise Concerns Over Extended Melatonin Use

A preliminary study presented at the American Heart Association’s Scientific Sessions 2025 finds long-term melatonin use among adults with insomnia is associated with higher rates of heart failure, hospitalization, and death, prompting experts to urge caution over prolonged nightly use.

Researchers reviewed five years of health records from 130,828 adults with chronic insomnia. Among them, 65,414 people had documented melatonin use for at least 12 months, while a matched group with insomnia had no recorded melatonin use.

The study found people in the long-term melatonin group were about 90% more likely to receive a new heart failure diagnosis than nonusers. Rates were 4.6% among melatonin users compared with 2.7% in the comparison group.

Lead author Dr. Ekenedilichukwu Nnadi said the findings suggest melatonin supplements “may not be as harmless as commonly assumed.” Researchers stressed the study does not prove melatonin caused the health problems.

The findings remain preliminary because they have not undergone full peer review or been published in a medical journal.

Hospitalizations and Death Rates Also Increase

Researchers reported additional risks among long-term users. Heart failure hospitalization rates reached 19% in the melatonin group, compared with 6.6% among nonusers.

Deaths from any cause were also higher among melatonin users during the five-year period. Researchers reported mortality rates of 7.8% in the melatonin group versus 4.3% in the comparison group.

Sleep medicine experts said the results should be interpreted carefully because the research is observational. Such studies can identify patterns but cannot establish direct cause and effect.

Carlos Egea, president of the Spanish Federation of Sleep Medicine Societies, said the findings “challenge the perception of melatonin as a benign chronic therapy.”

Researchers acknowledged major limitations in the analysis. The study relied on electronic health records and did not directly confirm how much melatonin participants took, whether they used over-the-counter products, or how consistently they used them.

Some participants classified as nonusers also may have taken melatonin without it appearing in medical records.

The researchers also lacked information on insomnia severity, psychiatric conditions, and use of other sleep medications, all of which may influence heart health.

Experts Recommend Medical Guidance for Chronic Insomnia

Melatonin is a hormone produced naturally by the body to regulate sleep-wake cycles. In the United States, it is sold as a dietary supplement and does not require approval from the Food and Drug Administration before reaching the market.

Health experts said melatonin may still help with short-term sleep problems such as jet lag, but chronic insomnia often requires broader treatment.

The National Center for Complementary and Integrative Health says short-term melatonin use appears safe for most people, but evidence on long-term safety remains limited. The agency also warns that some supplements may contain inaccurate ingredient levels.

Doctors advise people with complex medical conditions, pregnancy, epilepsy or those taking medications such as blood thinners to consult a health care provider before using melatonin regularly.

The American College of Physicians recommends cognitive behavioral therapy for insomnia as the initial treatment for chronic sleep problems. The therapy focuses on sleep habits, schedules, and behaviors linked to poor sleep.

Experts said patients should not panic over the new findings but should discuss long-term melatonin use with a doctor, especially if the supplement has become part of a nightly routine without medical supervision.

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