A popular over-the-counter sleep aid used by millions of Americans could pose serious cardiovascular risks when used long-term, according to groundbreaking research presented at the American Heart Association Scientific Sessions 2025.
Alarming Findings from Large-Scale Study
The comprehensive study examined health records of more than 130,000 adults suffering from insomnia who had no previous history of heart failure. Researchers conducted a detailed comparison between individuals who used melatonin supplements for at least one year and those who never used the sleep aid.
The results revealed a startling connection. Adults who consistently used melatonin for over a year demonstrated approximately 90% higher likelihood of developing heart failure within five years compared to non-users.
Consistent Risk Patterns Across Populations
Even when researchers analyzed data from the United Kingdom, where melatonin requires a prescription, the concerning pattern persisted. Patients who received at least two melatonin prescriptions filled 90 days apart still showed an 82% increased risk of heart failure.
The study uncovered even more dramatic outcomes for severe health events. Long-term melatonin users were nearly 3.5 times more likely to require hospitalization for heart failure compared to those who didn't use the supplement. Additionally, these users faced almost double the risk of dying from any cause during the five-year monitoring period.
Expert Perspectives on the Findings
Lead researcher Dr. Ekenedilichukwu Nnadi expressed significant concern about the results. "Melatonin supplements may not be as harmless as commonly assumed," he told Everyday Health. "It's a reminder that even over-the-counter supplements can have real physiological consequences."
Dr. Nnadi suggested that accessibility drives melatonin's popularity. "Because melatonin is inexpensive and available over the counter, it's often the only option many of my patients have," he explained, noting that prescription sleep medications remain difficult to access for many individuals.
The researcher also highlighted the complex relationship between sleep disorders and heart health. "We also know that insomnia itself is linked to higher cardiovascular risk. I started wondering whether long-term melatonin use might influence those same pathways — either in a protective or harmful way," Dr. Nnadi added.
Contrasting Views in Medical Community
While the study raises important concerns, some cardiologists urge caution in interpreting the results. Dr. Tamara Horwich noted that the research doesn't definitively prove melatonin directly causes heart problems.
"There are actually studies which have suggested that melatonin may have beneficial effects on the cardiovascular system, including protection against heart failure and cardiomyopathy," Dr. Horwich stated.
However, she acknowledged that the recent findings "raise an important signal that we have to consider" when recommending sleep aids to patients with existing cardiovascular concerns or those using melatonin long-term.
The study emphasizes the need for greater awareness about potential risks associated with prolonged use of over-the-counter sleep supplements and highlights the importance of consulting healthcare providers before beginning any long-term supplement regimen.
