Melatonin is a well-known go-to sleep aid, but researchers are still teasing out the supplement’s side effects, especially as long-term use becomes increasingly common. And now, a preliminary study out today suggests taking melatonin for more than a year may be linked to heart problems and early death.
Researchers studied the medical records of people with chronic insomnia, finding that those who were prescribed melatonin for at least a year were more likely to develop heart failure and more likely to die from any cause. The study has important limitations, the authors note, but the findings are motivation for scientists to look further into melatonin’s potential health risks.
“These findings challenge the perception of melatonin as a benign chronic therapy and underscore the need for
randomized trials to clarify its cardiovascular safety profile,” the researchers wrote in the study.
A hidden danger?
Our bodies naturally produce melatonin. Among other things, the hormone helps regulate our sleep-wake cycle.
In some countries like the U.K., officials have approved a synthetic version of melatonin for treating insomnia in people over 55, while in the U.S., melatonin is widely available over-the-counter as a supplement. Using melatonin for a night or two—say to beat jet lag— seems to be generally safe for adults (although not necessarily for children). But scientists know little about its long-term safety, particularly when it comes to the heart.
The authors analyzed data from the TriNetX Global Research Network, a large, international database containing tens of thousands of medical records. They specifically focused on adults diagnosed with chronic insomnia who were prescribed melatonin for a year or more—some 60,000 people. They then compared this group to similar people who had insomnia but who were not prescribed the sleep aid.
Over a five-year follow-up period, about 4.6% of melatonin patients developed heart failure, compared to 2.7% of non-melatonin patients—almost double the odds. People on melatonin also had a higher risk of being hospitalized for heart failure and were nearly twice as likely to die in general.
Caveats and caution
The team’s findings are set to be presented this week at the American Heart Association’s annual Scientific Sessions conference, but it carries some significant limitations.
The study is still preliminary, and it hasn’t gone through the typical peer review process. It is also observational and retrospective, meaning it can only demonstrate a correlation between chronic melatonin use and heart disease. And though the authors did try to control for important variables like where a patient lived, there are potential pitfalls in the data.
The database used in the study covers multiple countries, including places like the U.S. where melatonin is widely available over the counter. As a result, the authors admit that it’s entirely possible that some patients who weren’t prescribed melatonin were taking the supplement regardless, muddying the findings.
This research is far from a smoking gun proving the dangers of chronic melatonin use. But studies like this can build the case for more definitive research—ideally randomized and controlled trials—to find out for sure.
