Long-term melatonin use linked to 90% higher heart failure risk

Preliminary research presented at the American Heart Association's Scientific Sessions 2025 suggests a potential link between long-term use of melatonin, a sleep supplement, and an increased risk of heart failure, hospitalization for heart failure, and death among individuals with chronic insomnia. The study's findings do not definitively prove that melatonin causes these risks, but they raise concerns about the long-term safety of this commonly used supplement.

Melatonin, a hormone produced naturally by the brain's pineal gland, helps regulate the body's sleep-wake cycle, or circadian rhythm. Synthetic melatonin is chemically identical to this naturally occurring hormone and is often used for insomnia and jet lag.

The study divided participants based on their documented melatonin use, with those who had used the supplement for at least a year placed in the "melatonin group" and those without any melatonin use placed in the "non-melatonin group." Researchers found that adults with chronic insomnia who had used melatonin for over a year had about a 90% higher chance of developing heart failure over the following five years compared to non-users.

Heart failure, which affects about 6.7 million adults in the U.S., occurs when the heart cannot pump enough oxygen-rich blood to meet the body's needs.

Additional analysis revealed even higher risks when participants were limited to those who had filled at least two melatonin prescriptions at least 90 days apart. This group had an 82% higher risk of heart failure. People in the melatonin group were also nearly 3.5 times more likely to be hospitalized for heart failure and had a nearly twice as high risk of death during the five-year study period compared to those in the non-melatonin group.

While melatonin is often considered a safe and natural option for sleep support, researchers caution that its cardiovascular safety remains uncertain, particularly when taken for extended periods. The findings emphasize the need for further investigation into the potential risks associated with long-term melatonin use, especially given its widespread promotion as a harmless sleep aid.