Melatonin linked with higher heart failure rate in preliminary study

A preliminary study suggests a popular sleep aid could have negative effects on heart health, the American Heart Association said this week. 

Here’s what to know about what the study is saying about melatonin and heart failure:

Melatonin and heart failure

Big picture view:

Long-term use of melatonin was associated with a higher risk of heart failure diagnosis, according to a preliminary study announced this week by the American Heart Association. 

Dig deeper:

Researchers looked at five years of health data for adults with insomnia who had long-term melatonin use (12 months or more) in their records, compared to the data of other adults who had insomnia but no melatonin use in their records. 

Findings:

The data analysis found: 

• Adults with insomnia whose health records indicated long-term melatonin use had about a 90% higher chance of incident heart failure over 5 years compared with non-users
• A similar result (82% higher) when researchers analyzed people who had at least 2 melatonin prescriptions filled at least 90 days apart
• Those taking melatonin were nearly 3.5 times as likely to be hospitalized for heart failure when compared to those not taking melatonin 
• Participants in the melatonin group were nearly twice as likely to die from any cause than those in the non-melatonin group over the 5-year period

What they're saying:

"Melatonin supplements may not be as harmless as commonly assumed. If our study is confirmed, this could affect how doctors counsel patients about sleep aids," said Ekenedilichukwu Nnadi, M.D., lead author of the study and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn, New York.

Of note :

The study is a research abstract, meaning the findings are considered preliminary and are not yet peer-reviewed. Also, the association noted the data may not paint a complete picture because it only used prescription evidence to identify melatonin users, meaning those who use over-the-counter melatonin – such as in the U.S. – were classified in the data as nonusers. Melatonin is only available by prescription in the United Kingdom.

The other side:

Some experts are saying more insight is needed, and not to question yet the long-term use of melatonin. 

What they're saying:

"The findings are certainly provocative and warrant attention, especially given the widespread perception of melatonin as a benign, ‘natural’ sleep aid," Muhammad Rishi, an associate professor of clinical medicine and spokesperson for the American Academy of Sleep Medicine, who was not involved in the study, told the Washington Post. "However, the study is observational and based on electronic health record data, which limits its ability to establish causality."

The American Heart Association also said the link does not prove a cause-and-effect relationship between taking melatonin and heart failure, but rather raises safety concerns about the use of melatonin, which is widely available. 

Dig deeper:

The Washington Post also noted that these preliminary results appear to contradict existing research suggesting that melatonin might have health benefits for people with heart failure. 

What's next:

The study will be presented at the American Heart Association’s Scientific Sessions 2025, which is Nov. 7-10 in New Orleans.

What is heart failure? 

By definition:

According to the American Heart Association’s 2025 Heart Disease and Stroke Statistics, heart failure occurs when the heart can’t pump enough oxygen-rich blood to the body’s organs for them to function properly and is a common condition that affects 6.7 million adults in the U.S.

What is melatonin? 

Big picture view:

Melatonin is a hormone naturally produced in the body by the pineal gland, and it helps regulate the body’s sleep-wake cycle, the association explained. Melatonin levels increase during darkness and decrease during daylight.

Chemically identical synthetic versions of the hormone are often used to treat insomnia and jet lag.