NAIROBI, Kenya – Melatonin, the popular sleep aid often considered a safe natural remedy, may not be as harmless as many believe.
A new study has found that long-term use of melatonin is associated with a significantly higher risk of heart failure, hospitalisation, and death.
The findings, to be presented at the upcoming American Heart Association (AHA) conference, analysed health records from over 130,000 adults with chronic insomnia.
Researchers compared 65,414 patients who had been prescribed melatonin for at least a year with a matched control group of non-users.
Nearly Double the Risk of Heart Failure
Over a five-year follow-up period, 4.6 per cent of melatonin users developed heart failure compared to 2.7 per cent of non-users — a 90 per cent higher relative risk.
Sustained users, who refilled prescriptions at least twice over 90 days, showed an 82 per cent higher risk.
Hospitalisations were also significantly higher: 19 per cent of melatonin users were admitted for heart failure compared to 6.6 per cent of non-users — a 3.5-fold increase.
Meanwhile, 7.8 per cent of users died during the study period, nearly double the 4.3 per cent death rate among non-users.
Observational, Not Causal
Researchers caution that the study is observational, meaning it cannot prove melatonin directly causes heart problems.
Factors such as underlying health conditions, severity of insomnia, or lifestyle habits could also influence outcomes.
“Insomnia itself is known to increase cardiovascular risk,” the researchers noted, “so part of the association may stem from the condition being treated rather than the treatment itself.”
Limitations and Caution
The study did not capture over-the-counter melatonin use, which is widespread and could blur the true difference between groups.
Details on dosage, formulation, and long-term use beyond 12 months were also unavailable.
Additionally, as the study is being presented as a conference abstract, it has not yet undergone peer review.
Experts emphasise that while the relative risk appears high, the absolute increase in heart failure cases was modest — about 1.9 percentage points over five years.
What Experts Say
Cardiologists and sleep specialists have reacted cautiously. Some point out that earlier research suggested melatonin might benefit heart function due to its antioxidant properties.
Others urge restraint in interpretation until peer-reviewed results are published.
“People shouldn’t panic or stop taking melatonin abruptly,” one cardiologist advised. “But this is a timely reminder that ‘natural’ doesn’t always mean ‘risk-free.’”
Safer Alternatives
Melatonin, produced naturally by the pineal gland, regulates the body’s sleep-wake cycle and is often taken for insomnia, jet lag, or shift-work sleep issues.
While it is generally safe for short-term use, experts now advise against using it long-term without medical guidance — especially for individuals with heart disease or high blood pressure.
Doctors recommend non-drug therapies like cognitive-behavioural therapy for insomnia (CBT-I), which has been shown to improve sleep without the potential cardiovascular risks.
As the debate continues, one thing is clear: the world’s favourite “natural sleep supplement” may not be as benign as once thought.