Can too much melatonin harm your cardiac health? New study sounds alarm over heart failure

The American Heart Association on Monday said researchers analysing health data from tens of thousands of adults with chronic insomnia discovered that those who had been prescribed melatonin for over a year faced a greater likelihood of developing heart failure within five years than individuals who did not use the supplement. The study also found that melatonin users were more prone to hospitalisation for heart failure and had a higher overall risk of death compared with nonusers, according to The Washington Post.

The study, which has not yet undergone peer review, has received mixed responses from both sleep medicine specialists and cardiologists. Experts are advising the public to stay calm while emphasising the need for further research on the long-term use of melatonin.

Muhammad Rishi, an associate professor of clinical medicine and spokesperson for the American Academy of Sleep Medicine, who was not a part of the research, said, “The findings are certainly provocative and warrant attention, especially given the widespread perception of melatonin as a benign, ‘natural’ sleep aid." He added that the study is observational and relies on electronic health record data, which limits its ability to prove cause and effect.

The study used an international health records database and analysed five years of data from more than 130,000 adults diagnosed with insomnia.

Researchers identified roughly 65,000 participants who had been prescribed melatonin at least once and reported using it for at least a year. Over five years, about 3,000 of those taking prescription melatonin experienced heart failure for the first time, compared with nearly 1,800 people who were classified as nonusers.

Individuals were excluded from the study if they had a prior diagnosis of heart failure or had been prescribed other sleep medications. Participants identified as melatonin users were matched with others in the database who also had insomnia but no record of melatonin use. The researchers said that they adjusted for multiple factors that could affect a person’s risk of heart failure, including other existing health conditions.

"Melatonin is also a well-known antioxidant,” Oen-Hsiao, an associate professor of cardiovascular medicine at Yale School of Medicine, who was not involved in the research, said, and it may offer protective benefits against coronary artery disease, which can lead to heart failure. Some research also suggests that, when taken at the right time and dose, melatonin supplements can help regulate blood pressure. The new study appears to be “the only one that is saying that melatonin can cause heart failure,” Oen-Hsiao added, the report noted.

What is Melatonin?

Melatonin is a hormone produced by the pineal gland in the brain during the evening, signalling the body that it’s time to sleep. However, some physicians advise against using melatonin supplements for managing chronic insomnia, citing limited and inconsistent evidence of their effectiveness and a lack of research on long-term safety.

Sleep experts generally recommend small doses of melatonin to help correct disruptions in sleep timing, such as those caused by jet lag or shift work. In the United States, melatonin is available without a prescription, unlike in some other countries.

While both prescription and over-the-counter forms contain the same active ingredient, prescription versions are typically subject to stricter pharmaceutical regulations that ensure greater consistency in purity and dosage.

As per the report, Ekenedilichukwu Nnadi, the lead author of the new report and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn, advised individuals who have been using melatonin for years, particularly those with heart disease or risk factors, to consult their doctors.

“The takeaway isn’t that melatonin is ‘bad’ or that everyone should stop taking it. It’s that we shouldn’t assume something is risk-free just because it’s natural or sold over the counter," he said.