(CNN) — Long-term use of melatonin supplements may be linked with a higher risk of heart failure, according to new research — but does that mean people taking it as a sleep aid should stop using it now?
In a review of electronic medical records, thousands of adults who had chronic insomnia and took melatonin for a year or longer had a 90% higher chance of heart failure over the next five years, compared with participants who had the same health factors but didn’t take melatonin. Melatonin users were also more than three times as likely to be hospitalized for heart failure and about twice as likely to die from any cause.
But experts suggest holding off on seeing melatonin as a definite danger. The research had significant limitations, was not designed to be able to prove cause and effect, and contradicts previous studies that indicated positives for heart health.
The research also hasn’t yet been peer-reviewed or published in a journal but will be presented at the American Heart Association’s Scientific Sessions 2025 meeting taking place November 7-10.
“Melatonin supplements are widely thought of as a safe and ‘natural’ option to support better sleep, so it was striking to see such consistent and significant increases in serious health outcomes, even after balancing for many factors,” Dr. Ekenedilichukwu Nnadi, lead research author and chief resident in internal medicine at SUNY Downstate/Kings County Primary Care in Brooklyn, said in a news release.
However, “while the association we found raises safety concerns about the widely used supplement, our study cannot prove a direct cause-and-effect relationship,” Nnadi said. “This means more research is needed to test melatonin’s safety for the heart.”
Naturally occurring melatonin in the brain is a hormone produced by the pineal gland in response to darkness, to help the body wind down for sleep.
The melatonin in supplements can be extracted from the pineal glands of animals or synthetically produced via a chemical process.
In the United States, because melatonin is sold as a dietary supplement, manufacturers aren’t subject to the level of scrutiny involved in the US Food and Drug Administration’s safety measures and approval processes for drugs. This means melatonin supplements can contain significantly more of the active ingredient than advertised or necessary, as well as harmful hidden additives.
Chronic insomnia, experienced by 10% of the global population, is defined by taking more than 30 minutes to fall asleep or fall back to sleep up to three times weekly for more than three months. It can lead to problems with memory, daytime energy, mood, thinking and concentration, work or school performance, and one’s social life.
A doctor can help one determine whether insomnia is occurring on its own or because of an underlying factor, such as a medical condition or stressful life circumstance, and therefore determine the best ways to treat it — whether that’s adjusting your sleep routine, undergoing therapy for mental or emotional distress or cognitive behavioral therapy for insomnia, taking medication, or treating a medical condition.
Melatonin use and heart health
Melatonin supplements are often marketed as a safe sleep aid, but there hasn’t been sufficient data on long-term safety for cardiovascular health, the authors said.
The research team assessed more than 130,000 adults with health records in the TriNetX Global Research Network, a large international electronic database. They were about 55 years old on average, and 61.4% were women. Participants with melatonin use documented in medication entries in their health records for more than a year were classified as the melatonin group, whereas those without any record of melatonin use were in the “non-melatonin group.”
These factors lend themselves to a few important limitations, the authors and independent experts pointed out.
The database includes patients in countries that require a prescription for melatonin, such as the United Kingdom, and those that don’t, including the United States — so the control group may unknowingly include adults who take melatonin without a prescription, which wouldn’t be reflected in their medical records, Dr. Carlos Egea, who wasn’t involved in the research, said in a statement provided by the Science Media Centre. Egea is president of the Spanish Federation of Sleep Medicine Societies.
The researchers also didn’t have details on the severity of participants’ insomnia or whether they had any mental health issues, both of which can influence melatonin use and heart health risks, Nnadi said.
Insomnia has been associated with a higher risk of having a heart attack or stroke. Disrupted circadian rhythms — our body clocks in which melatonin plays a role — and insufficient sleep have been linked with greater odds of cardiovascular issues including heart failure.
Other limitations include a lack of information on dosage, the Council for Responsible Nutrition, a trade association for the dietary supplement and functional food industry, said in a statement. “Decades of consumer experience and multiple clinical studies indicate that low-dose, short-term supplementation is safe for healthy adults when used as directed,” the association added.
The research challenges previous studies, including a March analysis of four studies that found melatonin supplementation improved heart failure patients’ quality of life and cardiac function, Egea said.
Melatonin is also an antioxidant, and antioxidants help protect against damage to DNA by oxidative stress, an imbalance between free radicals and antioxidants in the body.
Before you take sleep aids
Many people turn to melatonin as a short- or long-term solution to sleep woes. But for some people, the supplement has been linked to various side effects including headaches, nausea, dizziness, drowsiness, stomach aches, confusion or disorientation, tremors, low blood pressure, irritability, mild anxiety and depression.
Before resorting to supplements, “speak to your doctor first about, for one, getting a proper diagnosis for your sleep difficulty and then discussing the appropriate course of treatment,” Dr. Marie-Pierre St-Onge, director of the Center of Excellence for Sleep & Circadian Research in the department of medicine at Columbia University Irving Medical Center, said in the American Heart Association news release. “People should be aware that (melatonin) should not be taken chronically without a proper indication.”
Healthy sleep hygiene involves limiting light exposure, screen time and consumption of food and alcohol in the few hours before bed. Your bedroom should be dark, cool and quiet.
If you still choose to supplement melatonin, pharmaceutical grade melatonin is best, experts told CNN in a 2022 report — look for a stamp showing that the independent nonprofit US Pharmacopoeia’s Dietary Supplement Verification Program has tested the product.