A new study presented at the American Heart Association’s annual meeting has sparked debate about melatonin, one of the most prescribed sleep aids in the UK. The research suggests that long-term melatonin use may be linked to a higher risk of heart failure, but experts say the evidence remains too limited to draw firm conclusions.
Melatonin has been prescribed in Britain for nearly 20 years, with 2.5 million prescriptions issued across England last year. The synthetic hormone mimics melatonin produced naturally by the brain, helping to regulate sleep cycles. It is generally considered safe for short-term use in adults and, under specialist guidance, for children with certain conditions such as ADHD or learning disabilities.
What the Study Found
The new study examined the electronic health records of about 130,000 adults diagnosed with sleep problems over a five-year period. Roughly half the participants took melatonin, while the others did not. According to the findings, people who used melatonin for at least a year were nearly three times more likely to be hospitalized with heart failure — 19 percent compared with 6.6 percent among non-users. Long-term users also showed higher rates of heart failure diagnosis and death from any cause.
Researchers matched both groups across 40 different factors, including age, existing health conditions, and medications. Still, the study established only correlation, not causation. This means the data cannot prove that melatonin directly causes heart failure.
Key Data Still Missing
Only a short 300-word summary of the study has been released so far, leaving out crucial details such as the melatonin dosage, severity of sleep disorders, and lifestyle factors. The study relied on large-scale medical databases rather than direct patient follow-ups, which can lead to gaps or inaccuracies.
Because healthcare systems differ widely, data from hospitals in various countries may not be fully comparable. Another complication is that melatonin is sold over the counter in the U.S. but available only by prescription in the UK. Some Americans classified as non-users may actually have been taking melatonin, skewing the results.
Understanding the Broader Context
Even if the participant groups were perfectly matched, another important question remains: why were some people prescribed melatonin while others were not? Those taking the drug may have had more severe sleep disturbances, which could reflect underlying health conditions such as heart disease. If so, melatonin could be a signal of existing problems rather than their cause.
Interestingly, earlier research has suggested that melatonin might protect the heart. Some studies reported improvements in symptoms and heart function among patients with heart failure who took melatonin as a supplement. These contradictions highlight the need for further investigation.
Conclusion
The study has not yet undergone peer review, and its findings should be viewed as preliminary. While the results deserve attention, they do not justify alarm. More research is needed to clarify whether long-term melatonin use affects heart health—and if so, in what ways.
For now, doctors advise patients to focus on proven sleep strategies: maintaining consistent bedtime routines, improving lifestyle habits, and addressing stress or mental health concerns. When these steps aren’t enough, short-term use of sleep aids like melatonin may still be reasonable under medical supervision.
The debate over melatonin and heart health is far from settled. For experts, this early evidence marks a beginning—not an endpoint—in understanding the supplement’s full effects.
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