Scientists have uncovered troubling associations between the long-term use of melatonin supplements and increased risks of heart failure and mortality. A large-scale review analyzing health records of over 130,000 adults with chronic insomnia, presented at the American Heart Association's Scientific Sessions 2025, revealed that those using melatonin for a year or more faced significantly higher chances of developing heart failure, hospitalization, and death compared to non-users—a finding that challenges the common perception of melatonin as a harmless sleep aid. Melatonin, a hormone naturally produced by the pineal gland that regulates the sleep-wake cycle, is widely consumed as an over-the-counter supplement for sleep disturbances and jet lag. Despite its natural origins, the study presented at the American Heart Association’s 2025 Scientific Sessions raises urgent safety concerns about prolonged usage, emphasizing the need for caution and further research. Researchers utilized the TriNetX Global Research Network, an international database of de-identified medical records, to identify adults diagnosed with chronic insomnia who had documented melatonin use exceeding 12 months. The melatonin group was matched by age and health status with a similar group of insomnia patients who never recorded melatonin use and excluded those with prior heart failure or other sleep medications. Incidence of heart failure, hospitalizations, and mortality over five years were compared between groups. Adults using melatonin long-term had approximately a 90% higher risk of new heart failure diagnoses (4.6% vs. 2.7%) and were nearly 3.5 times more likely to be hospitalized for heart failure than non-users. Furthermore, mortality risk was almost doubled in melatonin users over the study period. Although causality cannot be established, these alarming correlations warrant critical reevaluation of melatonin’s safety profile in chronic enthusiasts. Experts advise that melatonin is intended as a short-term remedy and encourage users to seek medical guidance for persistent insomnia and underlying health risks. These findings underscore the importance of tailored sleep therapies and comprehensive cardiovascular monitoring in patients reliant on melatonin supplements. REFERENCE: American Heart Association. "Think melatonin is safe? New research reveals a hidden heart risk." ScienceDaily. ScienceDaily, 4 November 2025. .