https://www.sciencedaily.com/releases/2025/11/251104012959.htm Skip to main content ScienceDaily --------------------------------------------------------------------- Your source for the latest research news Follow: Facebook X/Twitter Subscribe: RSS Feeds Newsletter New! Sign up for our free email newsletter. Science News from research organizations --------------------------------------------------------------------- Think melatonin is safe? New research reveals a hidden heart risk Long-term melatonin use may secretly strain the heart--raising the risk of failure, hospitalization, and death. Date: November 4, 2025 Source: American Heart Association Summary: Long-term melatonin use for sleep problems may come with unexpected heart dangers. Researchers found that chronic users were almost twice as likely to die and 3.5 times more likely to be hospitalized for heart failure. Though melatonin is widely regarded as harmless, experts now urge caution with extended use. Share: Facebook Twitter Pinterest LinkedIN Email FULL STORY --------------------------------------------------------------------- Melatonin's Hidden Heart Risk People using melatonin for more than a year faced dramatically higher risks of heart failure and death compared to non-users. Once considered a "natural" sleep fix, melatonin may pose hidden cardiovascular risks that call for closer scrutiny. Credit: Shutterstock Key Research Findings * A large review of health data from more than 130,000 adults with insomnia found that people who took melatonin for a year or longer were more likely to develop heart failure, be hospitalized for the condition, or die from any cause compared to those who didn't take the supplement. * While the study cannot prove that melatonin directly causes these outcomes, the strong association raises important safety questions about long-term use of this popular sleep aid. Researchers emphasize that more studies are needed to fully understand melatonin's impact on heart health and ensure it can be used safely. Long-Term Melatonin Use Linked to Higher Heart Failure Risk People who regularly take melatonin to improve sleep may face serious health risks. A preliminary study presented at the American Heart Association's Scientific Sessions 2025 found that adults with chronic insomnia who used melatonin for a year or longer were more likely to develop heart failure, be hospitalized for heart failure, and die from any cause than those who did not take the supplement. The findings will be discussed at the AHA's annual meeting, taking place Nov. 7-10 in New Orleans, a leading international event for cardiovascular science and clinical research updates. Melatonin is a hormone produced by the pineal gland that regulates the body's sleep-wake cycle. Its levels naturally rise in the dark and drop during daylight hours. Synthetic melatonin, which is chemically identical to the natural hormone, is widely used to treat insomnia (difficulty falling and/or staying asleep) and jet lag. In many countries, including the U.S., melatonin supplements can be purchased over the counter. However, because they are not regulated in the U.S., products can differ widely in purity and dosage. How the Study Was Conducted Researchers divided participants into two groups based on their medical records. Those who had taken melatonin for at least one year were classified in the "melatonin group," while individuals with no record of melatonin use were placed in the "non-melatonin group." "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. Investigating Heart Failure and Sleep Aid Safety Although melatonin is marketed as a safe and natural sleep remedy, little evidence exists on its long-term cardiovascular effects. The research team wanted to know whether long-term use could influence heart failure risk in people with chronic insomnia. According to the American Heart Association's 2025 Heart Disease and Stroke Statistics, heart failure occurs when the heart cannot pump enough oxygen-rich blood to sustain the body's organs. The condition affects about 6.7 million U.S. adults. To explore this question, scientists used data from the TriNetX Global Research Network, an international database of de-identified medical records. They reviewed five years of data on adults diagnosed with chronic insomnia who had documented melatonin use for more than a year. Each was matched with another person who also had insomnia but had never used melatonin. Individuals with a previous diagnosis of heart failure or who had been prescribed other sleep medications were excluded. The main analysis found: * Among adults with insomnia, those whose electronic health records indicated long-term melatonin use (12 months or more) had about a 90% higher chance of incident heart failure over 5 years compared with matched non-users (4.6% vs. 2.7%, respectively). * There was a similar result (82% higher) when researchers analyzed people who had at least 2 melatonin prescriptions filled at least 90 days apart. (Melatonin is only available by prescription in the United Kingdom.) A secondary analysis found: * Participants taking melatonin were nearly 3.5 times as likely to be hospitalized for heart failure when compared to those not taking melatonin (19.0% vs. 6.6%, respectively). * Participants in the melatonin group were nearly twice as likely to die from any cause than those in the non-melatonin group (7.8% vs. 4.3%, respectively) over the 5-year period. "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 other risk factors," Nnadi said. Expert Reactions and Caution From Sleep Researchers "I'm surprised that physicians would prescribe melatonin for insomnia and have patients use it for more than 365 days, since melatonin, at least in the U.S., is not indicated for the treatment of insomnia. In the U.S., melatonin can be taken as an over-the-counter supplement and people should be aware that it should not be taken chronically without a proper indication," said Marie-Pierre St-Onge, Ph.D., C.C.S.H., FAHA, chair of the writing group for the American Heart Association's 2025 scientific statement, Multidimensional Sleep Health: Definitions and Implications for Cardiometabolic Health. St-Onge, who was not involved in this study, is a professor of nutritional medicine in the division of general medicine and director of the Center of Excellence for Sleep & Circadian Research in the department of medicine at Columbia University Irving Medical Center in New York City. The study has several limitations. First, the database includes countries that require a prescription for melatonin (such as the United Kingdom) and countries that don't (such as the United States), and patient locations were not part of the de-identified data available to the researchers. Since melatonin use in the study was based only on those identified from medication entries in the electronic health record, everyone taking it as an over-the-counter supplement in the U.S. or other countries that don't require a prescription would have been in the non-melatonin group; therefore, the analyses may not accurately reflect this. Hospitalization figures were also higher than those for initial diagnosis of heart failure because a range of related diagnostic codes may be entered for the hospitalization, and they may not always include the code for a new diagnosis of heart failure. The researchers also lacked information on the severity of insomnia and the presence of other psychiatric disorders. "Worse insomnia, depression/anxiety or the use of other sleep-enhancing medicines might be linked to both melatonin use and heart risk," Nnadi said. "Also, while the association we found raises safety concerns about the widely used supplement, our study cannot prove a direct cause-and-effect relationship. This means more research is needed to test melatonin's safety for the heart." Study details, background and design: * The study included 130,828 adults (average age of 55.7 years; 61.4% women) diagnosed with insomnia. * The study data was from TriNetX, established in 2013, a growing global network of real-world, de-identified patient data available for research. * 65,414 participants had been prescribed melatonin at least once and reported taking it for at least a year. * A second group of people were examined for comparison (control group) -- those who had never been prescribed melatonin and were matched to the group taking melatonin on 40 factors including demographic information, health conditions and medications. * Participants were excluded if they had already been diagnosed with heart failure or had been prescribed other types of sleeping pills such as benzodiazepines. * The melatonin and control groups were matched for age, sex, race/ ethnicity, heart and nervous system diseases, medications for heart and nervous system diseases, blood pressure and body mass index. Researchers looked at electronic medical records from the five years after the matching date. * For the main findings, records were searched for codes related to an initial diagnosis of heart failure. Secondary findings included codes for hospitalization related to heart failure or death. * Following the initial analyses, researchers validated the credibility of their findings by conducting a sensitivity analysis. This involved slightly changing the criteria: they required participants in the melatonin group to have filled at least two melatonin prescriptions that were at least 90 days apart. This adjustment aimed to determine whether the extended duration of confirmed melatonin prescriptions influenced the outcomes. Note: The study featured in this article is a research abstract. Abstracts presented at American Heart Association's scientific meetings are not peer-reviewed, and the findings are considered preliminary until published as full manuscripts in a peer-reviewed scientific journal. * RELATED TOPICS + Health & Medicine o Mental Health Research o Today's Healthcare o Heart Disease o Diseases and Conditions o Pharmacology o Hypertension o Hormone Disorders o Chronic Illness * RELATED TERMS + Sleep apnea + Obstructive sleep apnea + Sleep + Sleep disorder + Circadian rhythm sleep disorder + Heart failure + Delayed sleep phase syndrome + Heart --------------------------------------------------------------------- Story Source: Materials provided by American Heart Association. Note: Content may be edited for style and length. --------------------------------------------------------------------- Cite This Page: * MLA * APA * Chicago American Heart Association. "Think melatonin is safe? New research reveals a hidden heart risk." ScienceDaily. ScienceDaily, 4 November 2025. . American Heart Association. (2025, November 4). Think melatonin is safe? New research reveals a hidden heart risk. ScienceDaily. Retrieved November 9, 2025 from www.sciencedaily.com/releases/2025/11 /251104012959.htm American Heart Association. "Think melatonin is safe? New research reveals a hidden heart risk." ScienceDaily. www.sciencedaily.com/ releases/2025/11/251104012959.htm (accessed November 9, 2025). Explore More from ScienceDaily --------------------------------------------------------------------- RELATED STORIES --------------------------------------------------------------------- Music Makes Us Move Even When We Don't Like It Feb. 11, 2025 The pleasurable urge to move to music -- to groove -- appears to be a physiological response independent of how much we generally enjoy music, according to a new article. That groove response is so ... Heart Attack Significantly Increases Risk of Other Health Conditions Feb. 16, 2024 Having a heart attack significantly increases the risk of developing other serious long-term health conditions, a major new study shows. Researchers analyzed more than 145 million records covering ... Changed Gene Expression After Heart Surgery Extends Cardiomyocyte Regeneration June 24, 2022 While lower vertebrates can repair their adult hearts after a heart attack, mammals -- including humans -- cannot. The ability to regenerate dead muscle tissue in mammalian hearts disappears just a ... How the Timing of Dinner and Genetics Affect Individuals' Blood Sugar Control Jan. 25, 2022 Eating dinner close to bedtime, when melatonin levels are high, disturbs blood sugar control, especially in individuals with a genetic variant in the melatonin receptor MTNR1B, which has been linked ... Undetected Early Heart Damage Raises Risk of Death in Hospitalized COVID-19 Patients May 10, 2021 First-phase ejection fraction, a possible indicator of heart failure, is a strong predictor of survival in hospitalized COVID-19 patients, according to a new study. Hospitalized patients who had ... Worms Reveal Why Melatonin Promotes Sleep Nov. 16, 2020 Melatonin is used as a dietary supplement to promote sleep and get over jet lag, but nobody really understands how it works in the brain. Now, researchers show that melatonin helps worms sleep, too, ... --------------------------------------------------------------------- TRENDING AT SCITECHDAILY.com --------------------------------------------------------------------- Thought to Be Impossible: Scientists Show Quantum Light Could Be Beamed Up to Space Concerning New Research Reveals That the Ground Beneath Arizona Is Collapsing Popular Diabetes Drug Metformin May Cancel Out Exercise Benefits, Study Warns Gray Hair May Be Your Body's Secret Cancer Defense Print Email Share --------------------------------------------------------------------- Breaking this hour --------------------------------------------------------------------- * Mysterious Gas Found in Deep Space * Dark Energy Might Be Changing * Microbes That Breathe Rust * Life Discovered Where Nothing Should Survive * The Desert Plant That Thrives at 120degF * 9,000-Year-Old Antarctic Ice Collapse * Hidden Heat Beneath Saturn's Moon Hints ... * A Crystal That Could Transform Quantum Tech * "Bizarre" Quantum Discovery Defies Physics * DNA Could Transform How We Make Medicines Trending Topics this week --------------------------------------------------------------------- HEALTH & MEDICINE Personalized Medicine Pharmacology Healthy Aging MIND & BRAIN Perception Behavior Child Development LIVING & WELL Healthy Aging Skin Care Behavior Strange & Offbeat --------------------------------------------------------------------- HEALTH & MEDICINE Rare Desert Berry Could Transform Diabetes Treatment Mini Llama Proteins Show Promise for Alzheimer's Treatment Scientists Just Found a Hidden Genetic Flaw That Slowly Steals Strength MIND & BRAIN Scientists Find Mind Trick That Unlocks Lost Memories It Sounds Creepy, but These Scientific Breakthroughs Could Save Lives Your IQ May Determine How Well You Hear in a Crowd LIVING & WELL Bananas Could Be Ruining Your Smoothie's Health Benefits Your Gut Microbes Might Be Turning Fiber Into Extra Calories Forget Fiber. Science Just Found the Foods That Really Help Constipation Toggle navigation Menu SD * SD + Home Page + + Top Science News + + Latest News * Home + Home Page + + Top Science News + + Latest News * Health + View all the latest top news in the health sciences, or browse the topics below: Health & Medicine o Allergy o Cancer o Cold and Flu o Diabetes o Heart Disease o ... more topics Mind & Brain o ADD and ADHD o Alzheimer's o Headaches o Intelligence o Psychology o ... more topics Living Well o Parenting o Child Development o Stress o Nutrition o Fitness o ... more topics * Tech + View all the latest top news in the physical sciences & technology, or browse the topics below: Matter & Energy o Chemistry o Fossil Fuels o Nanotechnology o Physics o Solar Energy o ... more topics Space & Time o Black Holes o Dark Matter o Extrasolar Planets o Solar System o Space Telescopes o ... more topics Computers & Math o Artificial Intelligence o Mathematics o Quantum Computers o Robotics o Virtual Reality o ... more topics * Enviro + View all the latest top news in the environmental sciences, or browse the topics below: Plants & Animals o Agriculture and Food o Biology o Biotechnology o Extinction o Microbes and More o ... more topics Earth & Climate o Climate o Earthquakes o Geology o Global Warming o Pollution o ... more topics Fossils & Ruins o Anthropology o Archaeology o Dinosaurs o Evolution o Paleontology o ... more topics * Society + View all the latest top news in the social sciences & education, or browse the topics below: Science & Society o Arts & Culture o Economics o Privacy Issues o Public Health o Sports o ... more topics Business & Industry o Computers & Internet o Energy & Resources o Engineering o Medical Technology o Transportation o ... more topics Education & Learning o Creativity o Educational Psychology o Infant & Preschool o Learning Disorders o STEM Education o ... more topics * Quirky + Top News + + Human Quirks + Odd Creatures + Bizarre Things + Weird World Keyword:[ ]Search Free Subscriptions --------------------------------------------------------------------- Stay informed with ScienceDaily's free email newsletter, updated daily and weekly. Or view our many newsfeeds in your RSS reader: * Email Newsletter * RSS Feeds Follow Us --------------------------------------------------------------------- Keep up to date with the latest news from ScienceDaily via social networks: * Facebook * X / Twitter Have Feedback? --------------------------------------------------------------------- Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions? * Leave Feedback * Contact Us About This Site | Staff | Contribute | Advertise | Privacy Policy | Editorial Policy | Terms of Use Copyright 1995-2025 ScienceDaily or by other parties, where indicated. All rights controlled by their respective owners. Content on this website is for information only. It is not intended to provide medical or other professional advice. Views expressed here do not necessarily reflect those of ScienceDaily, contributors or partners. Financial support for ScienceDaily comes from advertisements and referral programs.