Prolonged Melatonin Use May Increase Heart Failure Risk by 90%

A preliminary study released by the American Heart Association suggests that prolonged use of melatonin may be associated with a 90% higher risk of heart failure in people with chronic insomnia. The analysis, published on ScienceDaily on August 29, 2026, evaluated records of more than 130 thousand adults. Half of them used melatonin for at least one year. The results do not prove that the supplement causes heart problems, but they raise an alert about the safety of continuous use.

Among adults with chronic insomnia who took melatonin for 12 months or more, about 4.6% developed heart failure within five years, compared to 2.7% of those who did not use the hormone. The risk of hospitalization for heart failure was 3.5 times higher in the melatonin group: 19% required hospitalization, while the control group rate was 6.6%. All-cause mortality was also nearly double among long-term users. The data came from electronic health records of more than 130 thousand adults with insomnia.

Experts emphasize that the study is observational and does not establish a cause-and-effect relationship. Chronic insomnia itself is already associated with higher risk of cardiovascular problems, which may confound the results. Physician Ekenedilichukwu Nnadi, lead author of the study, stated that melatonin supplements may not be as harmless as assumed. He noted that if the findings are confirmed, this could change how doctors advise patients on sleep aids.

Melatonin is a hormone naturally produced by the body and, in low doses and for short periods, is considered safe. In Brazil, it is sold as a dietary supplement without requiring a prescription. The issue, according to researchers, is daily, prolonged use without medical guidance. More studies are needed to understand the mechanisms and confirm the risks before changing recommendations.

The research also contrasts with previous studies that suggested benefits of melatonin for the heart. One March analysis, for example, indicated that supplementation improved quality of life and cardiac function in patients with heart failure. However, those studies were smaller and involved different populations. The scientific community has not yet reached a consensus on prolonged use of the supplement.