New study finds long-term use of sleep pill melatonin may raise risk of heart failure and death

Melatonin, a popular sleep aid long considered harmless, has now been linked to a higher risk of heart attack, heart failure, and death, according to a new study.

The research, set to be presented at the American Heart Association (AHA) conference, examined the long-term impact of melatonin use on heart health.

It analysed medical records from 130,828 adults with chronic insomnia. Of these, 65,414 had been prescribed melatonin for at least a year — forming the “melatonin group” — while the rest served as a matched control group of non-users.

Participants were matched across about 40 factors, including age, sex, race or ethnicity, pre-existing conditions, medications, body mass index, and blood pressure. Those with prior heart failure or who used other sleep medications were excluded to ensure accurate results.

Melatonin is a hormone naturally produced by the pineal gland that helps regulate the body’s sleep-wake cycle. Its production rises in the evening to promote sleepiness and falls in the morning with exposure to light.

Insomnia

Supplement forms are commonly used to treat insomnia, jet lag, shift work–related sleep issues, or delayed sleep-wake phase disorder.

Over a five-year follow-up, 4.6 per cent of long-term melatonin users developed heart failure compared to 2.7 per cent of non-users — about a 90 per cent higher relative risk. A separate analysis of sustained users (those with two or more prescriptions filled at least 90 days apart) showed an 82 per cent increased risk.

Hospitalisations were also higher: 19 per cent of melatonin users were admitted for heart failure, compared to 6.6 per cent of non-users — a roughly 3.5-fold increase. Moreover, 7.8 per cent of melatonin users died during the study period, versus 4.3 per cent of non-users, nearly doubling the risk of death.

The findings suggest a strong association between long-term prescribed melatonin use and increased rates of heart failure, hospitalisation, and mortality. However, researchers stress that this is an observational study and cannot prove causation. Other factors — including the severity of insomnia, lifestyle, or underlying health issues — may have influenced the outcomes. Insomnia itself is known to elevate cardiovascular risk, which could partly explain the results.

Study limitations

The study also has limitations. Over-the-counter melatonin use — which is widespread — was not included in electronic health records, meaning some non-users may have actually taken it. Dosage, formulation, and duration beyond 12 months were also not detailed. Furthermore, as the results are based on a conference abstract, they have not yet undergone peer review.

In practical terms, the absolute risk increase between users and non-users is modest — about 1.9 percentage points over five years — though the relative risk is significant.

Researchers say the results highlight the need for caution when using melatonin long-term, particularly for heart health. They advise patients and clinicians to weigh benefits against potential risks and consider safer, non-drug approaches such as cognitive-behavioural therapy for insomnia.

The study, which has not yet been peer-reviewed, has sparked mixed reactions from sleep and heart specialists. Experts caution the public “not to panic” and emphasise the need for more research on the long-term safety of melatonin.

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• Heart Attack
• heart health
• heart failure
• insomnia
• melatonin
• sleep pill
• American Heart Association
• New study finds long-term use of sleep pill melatonin may raise risk of heart failure and death
• Health

The findings appear to contradict earlier research suggesting melatonin may actually benefit heart failure patients. Still, cardiologists note that the current study’s design makes it difficult to determine whether melatonin directly contributes to heart failure or whether other factors are at play.

Low doses

Sleep experts typically recommend low doses of melatonin for specific sleep-timing issues, such as jet lag or shift work. While both prescription and over-the-counter versions contain the same active ingredient, the prescription forms are more tightly regulated for consistency and purity.

Quality sleep is vital for cardiovascular health, as poor sleep is linked to higher heart rates, elevated blood pressure, and a greater risk of cardiac events. Melatonin also has antioxidant properties that may help protect against coronary artery disease and assist in regulating blood pressure when taken appropriately.

Though generally safe for short-term use, melatonin can cause side effects such as daytime drowsiness, dizziness, headaches, nausea, vivid dreams, or changes in heart rate or blood pressure.

Emerging research now suggests that prolonged use could carry additional risks — including higher chances of heart failure or hospitalisation — although a direct cause-and-effect relationship has yet to be proven.

With limited data on its long-term safety, experts urge caution — especially for people with existing heart conditions or those taking other medications.