With a third of adults suffering from chronic insomnia, popular over-the-counter melatonin is promoted as a safe sleep aid. However, a recent study has reported the long-term effects of melatonin on the cardiovascular system.

The study published by the American Heart Association (AHA) found that over 5 years, people who take melatonin were more likely to be diagnosed with heart failure. Although it cannot prove cause and effect, it does raise concerns, as melatonin is widely used. However, the AHA study is a research abstract, and the findings should be considered preliminary until a scientific journal publishes them.

“This is a first study showing an association, meaning, not necessarily cause and effect, but it is showing when they studied melatonin for chronically used for a year versus non-melatonin,” Rockville High School nurse Joan Grocki said.

Melatonin is a naturally produced hormone produced in the body in the pineal gland, which helps regulate the night-day cycle. A chemically similar synthetic version is widely available for purchase over the counter.

“It is not approved by the FDA, the Food and Drug Administration, meaning they are not checking it for quality and strength,” said Grocki. “Anybody could make anything and put it in there and sell it over the counter.”

With the popular belief that melatonin is a safe supplement for those with insomnia, the data on its long-term cardiovascular effects are lacking.

Researchers from the AHA found that adults who have taken melatonin long-term (over 1 year) had about a 90% higher chance of heart failure over 5 years compared to people who didn’t. (4.6% vs. 2.7%) They also found that in the United Kingdom, people who had two prescriptions filled at least 90 days apart had an 82% higher chance of heart failure. Moreover, people who took melatonin were found to be 3.5 times more likely to be hospitalized for heart failure compared to people who didn’t. (19.0% vs. 4.3%)

Melatonin, contrary to popular belief, is not indicated for the treatment of insomnia, nor should it be taken habitually without a proper doctor’s indication.

“If you’re really having trouble [sleeping], then you need to do two things. I would recommend talking to a sleep specialist,” said Grocki. “But also start with your PCP (primary care physician) to see what other, if any, underlying issues you have.”