Long-Term Melatonin Use Linked to Increased Heart Failure Risk in Insomnia Patients, Study Finds
A preliminary study suggests adults with insomnia who used melatonin supplements for at least one year had significantly higher rates of heart failure diagnosis, hospitalization and death compared to non-users, raising important safety concerns about the widely available sleep aid.
A preliminary study to be presented at the American Heart Association's Scientific Sessions 2025 found that long-term use of melatonin supplements was associated with significantly higher risks of heart failure diagnosis, hospitalization and death among adults with chronic insomnia. The research, which analyzed five years of health records for more than 130,000 adults with insomnia, raises important safety questions about a supplement widely considered harmless and readily available without prescription in many countries.
Researchers reviewed electronic health records from the TriNetX Global Research Network, comparing 65,414 adults who had used melatonin for at least one year with a matched control group of insomnia patients who had never used the supplement. The analysis revealed that those in the melatonin group had approximately 90% higher chance of developing heart failure over five years compared to non-users (4.6% vs. 2.7%, respectively). According to the American Heart Association's 2025 Heart Disease and Stroke Statistics, heart failure affects 6.7 million adults in the U.S. and occurs when the heart cannot pump enough oxygen-rich blood to the body's organs.
Secondary findings were even more striking, showing that participants taking melatonin were nearly 3.5 times as likely to be hospitalized for heart failure (19.0% vs. 6.6%) and nearly twice as likely to die from any cause (7.8% vs. 4.3%) compared to those not taking the supplement. "Melatonin supplements may not be as harmless as commonly assumed," said Dr. Ekenedilichukwu Nnadi, lead author of the study and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn, New York. "If our study is confirmed, this could affect how doctors counsel patients about sleep aids."
The study's limitations include the fact that melatonin use was based only on medication entries in electronic health records, meaning those taking over-the-counter supplements in countries like the U.S. would have been classified in the non-melatonin group. Researchers also lacked information on insomnia severity and the presence of other psychiatric disorders. Dr. Marie-Pierre St-Onge, chair of the writing group for the American Heart Association's 2025 scientific statement on sleep health, expressed surprise that physicians would prescribe melatonin for long-term insomnia treatment, noting that "in the U.S., melatonin can be taken as an over-the-counter supplement and people should be aware that it should not be taken chronically without a proper indication."
While the association between melatonin and increased cardiovascular risk cannot prove cause and effect, researchers emphasized the need for more investigation into the supplement's safety profile. The findings are particularly significant given melatonin's widespread availability and perception as a natural sleep aid. More information about the study can be found in the American Heart Association's abstract in the Scientific Sessions 2025 Online Program Planner. The full study details will be presented at the association's Scientific Sessions 2025 meeting in New Orleans from November 7-10.