Melatonin helps sleep but hides doubts! Study: Long-term users have 89% higher risk of heart failure diagnosis

Melatonin is often used to improve sleep, but a yet-to-be-peer-reviewed study found that adults with insomnia who had been prescribed melatonin for at least 1 year had a higher rate of heart failure diagnoses within 5 years than those who had not been prescribed it. Schematic diagram. (File photo)

[Compiled by Chen Chengliang/Comprehensive Report] Many people regard melatonin as a sleep aid supplement and use it on their own when they have insomnia. However, a study covering more than 130,000 adults with insomnia found that those who used melatonin for a long time were more likely to be diagnosed with heart failure within 5 years, with a relative risk 89% higher. The research has not yet been peer-reviewed, and the results do not prove that melatonin directly causes heart failure.

The science news website "Science Alert" recently reported that the American Heart Association (AHA) published a summary of this research at the November 2025 Annual Scientific Meeting. The research team analyzed the electronic medical records of 130,828 adults with insomnia, compared those with melatonin prescription records for at least 1 year and those with no relevant prescription records, and observed the health outcomes of the two groups over the next 5 years.

The study found that among those who had a melatonin prescription record for at least 1 year, the proportion of heart failure diagnosed within 5 years was 4.6%, compared with 2.7% among those who had no relevant prescription record. The former was relatively higher at about 89%. Another analysis found that the long-term use group was about 3.5 times more likely to be hospitalized for heart failure than the control group; the rate of all-cause death was 7.8%, higher than the 4.3% in the control group.

These numbers reflect differences between the two groups of subjects and do not directly prove that melatonin caused heart failure or death. The study used prescription records to estimate medication use, but did not directly investigate everyone's actual medication use. In the United States, melatonin can be purchased without a prescription, so people without a prescription record may also take it by themselves, affecting the comparison results between the two groups.

Saudi Arabian regulator issues safety signal

The Saudi Food and Drug Administration (SFDA) issued a safety signal on melatonin and the risk of heart failure in April 2026. After reviewing global case notifications and related studies, the agency believes that the existing evidence suggests that there may be a causal link between the two. This safety signal is not a ban on sales, nor does it mean that causation has been proven.

Melatonin is a hormone naturally secreted by the human body and is involved in regulating the biological clock of sleep and wakefulness. The American Heart Association points out that this study raises questions about the safety of long-term use of melatonin, but further research is needed to confirm.