It’s easy to jump to conclusions when you read a headline that suggests the buzzy sleep supplement melatonin is linked with heart failure. While recent research presented at the American Heart Association’s Scientific Sessions did find a link between long-term melatonin use and a higher risk of heart failure, the exact reason for this is muddled.
Melatonin is a hormone that your brain makes in response to darkness, according to the National Center for Complementary and Integrative Health (NCCIH). It helps to regulate your circadian rhythm (your internal clock), and can help you to fall asleep. But melatonin also comes in supplement form, which is designed to help gear your body up to go to sleep.
Melatonin use has exploded in the US over the past few years, with research finding that use of the supplement quintupled between 1999 and 2018. Now about two in every 100 people say they take melatonin supplements to help them sleep.
Doctors stress that the findings don’t mean that people who take melatonin will develop heart failure, but they do say this is a good time to check in about your own melatonin use and what it means for your health. With that in mind, here’s what the study found, plus why it should make you rethink your relationship with the supplement.
What did the study find?
For the study, which has not yet been published, researchers analyzed data from nearly 131,000 adults with an average age of 55.7 years who had been diagnosed with insomnia. Of those, 65,414 had been prescribed melatonin supplements at least once and said they took it for at least a year.
After crunching the data, the researchers discovered that people who took melatonin for 12 months or more had about a 90% higher risk of developing heart failure over five years compared to those who didn’t take the supplement. (Worth noting: Overall numbers were still low. Researchers found that 4.6% of people taking melatonin developed heart failure compared to 2.7% of those who didn’t take melatonin.)
The researchers also discovered that there was an 82% higher risk of developing heart failure in people who had at least two melatonin prescriptions filled at least 90 days apart. (In the U.K., melatonin is only available by prescription, while it’s commonly taken OTC in the U.S.)
A few more things worth pointing out: People who took melatonin were nearly 3.5 times as likely to be hospitalized for heart failure compared to those who didn’t take melatonin. People in the melatonin group were also nearly twice as likely to die from any cause during the five-year study period vs. those who didn’t take melatonin.
“Since there was very little large-scale data on melatonin’s long-term effects on the heart, it felt like an important question to study,” Ekenedilichukwu Nnadi, MD, lead study author and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn, New York, tells SELF.
Doctors say it’s tough to draw conclusions from this.
It’s easy to interpret these findings as taking melatonin will give you heart failure. But even Dr. Nnadi says that’s not the case. “Right now, we can’t say for sure whether melatonin itself is causing harm,” he says. “Our study only shows an association, not causation.”
Christopher Winter, MD, sleep specialist at Charlottesville Neurology and Sleep Medicine and author of The Sleep Solution: Why Your Sleep Is Broken and How to Fix It, agrees. “There are lots of associations,” he tells SELF. “There is a clear association between carrying a lighter and developing lung cancer, but that doesn’t mean that lighters cause lung cancer.”
Dr. Winter points out that people who are more likely to use melatonin—shift workers, international travelers, and those who struggle with sleep—are already at an increased risk for heart issues. Cheng-Han Chen, MD, an interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, agrees. “Poor sleep quality is definitely associated with future risk of cardiovascular disease,” he tells SELF. “Just taking melatonin could be a marker for people who have worse sleep quality and more sleep disturbances.”
People who exercise regularly tend to sleep better and have a lower risk of heart disease, making them unlikely to use melatonin regularly, Dr. Winter notes. People who rely on melatonin to sleep may also have a condition like sleep apnea, which Dr. Winter says is a “massive cardiovascular risk factor and often mimics insomnia.”
At least one study published in 2020 found that melatonin had a positive effect on people with heart failure, making things even more confusing, Jamie Alan, PhD, an associate professor of pharmacology and toxicology at Michigan State University, tells SELF.
Ultimately, it’s important to dive into why people need help sleeping in the first place—because that may be driving the increased risk of heart failure, Alan says. “Is it stress? And is it the stress that has an impact rather than the melatonin?” she says.
“My guess is the risk is coming from the circadian disruption and not the chemical itself,” Dr. Winter says.
Still, this is a solid time to rethink your own melatonin use.
While a lot more work needs to be done to explore this link, doctors say it’s a good reminder to revisit your melatonin use if you’re taking the supplement on a regular basis.
Practice guidelines from the American Academy of Sleep Medicine (AASM) clearly state that there’s not enough evidence on the effectiveness or safety of using melatonin supplements for chronic insomnia to recommend its use. Instead, AASM recommends using melatonin to help with sleep timing, like struggling with jet lag or having trouble getting used to sleep after late-night shift work. “In the short term, it’s perfectly fine,” Dr. Chen says.
“I generally don’t recommend using it every night for years,” Dr. Nnadi says. “It’s best to use the lowest effective dose, for the shortest possible time, and ideally under medical guidance.” An effective dose can be as low as 0.5 milligrams, even though melatonin usually comes in 5 milligram and 10 milligram doses for adults, Alan says.
But if you’re having trouble conking out on a regular basis and have been popping melatonin to try to help, Dr. Nnadi recommends taking a different tactic. “The most effective and sustainable approach is improving sleep habits—things like keeping a consistent sleep schedule, avoiding screens before bed, limiting caffeine and alcohol, and creating a calm bedtime routine,” he says. “Cognitive behavioral therapy for insomnia is also highly effective and often works better than medication in the long run.”
