As melatonin's terrifying link to fatal heart condition is revealed, experts weigh in on sleep aid's safety

Relying on melatonin supplements to fall asleep may increase the risk of suffering deadly heart failure, a study suggests.

Researchers in New York combed through health records from more than 130,000 adults suffering from insomnia who had taken melatonin, a supplement that helps the brain regulate its sleep-wake cycle, for at least a year.

Compared to people with insomnia who didn't take the sleep supplement, melatonin users were 90 percent more likely to be diagnosed within five years with heart failure, which occurs when the heart can no longer pump enough blood throughout the body.

Melatonin users were also three times more likely to be hospitalized for heart failure than their peers who didn't take it.

And those who used melatonin were nearly twice as likely to die from any cause in five years compared to non-users.

Melatonin, available over the counter without a prescription, is a hormone naturally produced by the brain's pineal gland to regulate circadian rhythm, the body's natural sleep-wake cycle. Levels rise in the evening to promote drowsiness and fall by morning so you can be awake and functioning during the day.

The study has not yet been peer reviewed, and researchers cautioned additional studies are needed to hone in on the exact relationship between melatonin and heart failure, which affects 7 million Americans and kills nearly 500,000 every year.

In some cases, insomnia has been an early sign of heart failure, as symptoms like shortness of breath or high blood pressure can make it difficult to sleep.

'Melatonin supplements may not be as harmless as commonly assumed,' Dr Ekenedilichukwu Nnadi, lead study author and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in New York City, said in a press release. 'If our study is confirmed, this could affect how doctors counsel patients about sleep aids.'

Physicians not involved with the study, however, told the Daily Mail that they 'would not recommend abrupt discontinuation' of melatonin until more research is done.

'The study in question was an observational analysis of health-record data that shows an association between melatonin use and heart failure, not causation,' Dr Chelsie Rohrscheib, a neuroscientist and head of sleep at Wesper, who was not involved in the research, told the Daily Mail.

'Additional research is required to answer whether using melatonin is the driving factor, or whether people who use long-term melatonin have a higher incidence of using melatonin due to existing sleep issues, like insomnia, and these sleep issues are actually the driving factor for heart failure.

'At this time, there is no clear evidence that melatonin usage leads to heart failure.

The findings come as more than one in four Americans, about 67 million, report taking melatonin at least once a year.

The study, which is being presented this week at the American Heart Association Scientific Sessions in New Orleans, looked at 130,828 adults who were diagnosed with insomnia. The average age was 56, and more than 61 percent of participants were women.

Of those, 65,414 participants had been prescribed melatonin at least once and reported taking it for at least a year. Melatonin supplements are available over the counter in the US without a prescription, but are prescription-only in the UK.

There was also a control group who had insomnia but had never taken melatonin.

The researchers combed through the records to find diagnoses of heart failure, as well as hospitalizations and deaths from the condition.

The team found that among adults with insomnia, those who used melatonin long term had a 4.6 percent chance of developing heart failure within five years. Those who didn't use the supplements, however, had a 2.7 percent chance, making melatonin users 90 percent more likely to develop heart failure.

And people in the UK who had at least two melatonin prescriptions filled at least 90 days apart were at an 82 percent increased risk of heart failure.

Additionally, melatonin users had a 19 percent chance of being hospitalized for heart failure compared to 6.6 percent of non-users, making those who rely on melatonin 3.5 times more likely to end up in the hospital.

Participants in the melatonin group were also twice as likely to die from any cause within five years compared to people who didn't take melatonin.

'Melatonin supplements are widely thought of as a safe and "natural" option to support better sleep, so it was striking to see such consistent and significant increases in serious health outcomes, even after balancing for many other risk factors,' Nnadi said in the release.

'I'm surprised that physicians would prescribe melatonin for insomnia and have patients use it for more than 365 days, since melatonin, at least in the US, is not indicated for the treatment of insomnia,' Dr Marie-Pierre St-Onge, chair of the writing group for American Heart Association's 2025 scientific statement, who was not involved in the study, said in a statement.

'In the US, melatonin can be taken as an over-the-counter supplement and people should be aware that it should not be taken chronically without a proper indication.'

There were several limitations to the new study, including relying on records where melatonin use was officially documented - the actual number of people using melatonin worldwide is much higher.

'The dataset also can't reliably capture over-the-counter use of melatonin, the dosage, or product quality, which are notoriously variable in the US supplement market,' Rohrscheib told the Daily Mail.

'Anyone with chronic sleep issues such as lower than recommended nightly sleep times, insomnia or other sleep disorders should speak to their doctor about health risks, including cardiovascular disease.'

The researchers said peer review and additional studies are needed.

'Worse insomnia, depression/anxiety or the use of other sleep-enhancing medicines might be linked to both melatonin use and heart risk,' Nnadi said.

'Also, while the association we found raises safety concerns about the widely used supplement, our study cannot prove a direct cause-and-effect relationship. This means more research is needed to test melatonin’s safety for the heart.'