Melatonin Linked to Higher Heart‑Failure Risk

A preliminary study presented at the American Heart Association Scientific Sessions 2025 found adults with chronic insomnia who used melatonin for a year or more had higher rates of heart‑failure diagnosis, heart‑failure hospitalization and all‑cause death over five years compared with nonusers. Researchers reviewed electronic health records for 130,828 adults (mean age ~56) and reported that 4.6% of chronic melatonin users developed heart failure versus 2.7% of nonusers, while hospitalization rates were about 19% versus 6.6% and overall mortality was also higher among users. The study is observational and presented as a research abstract, not yet peer‑reviewed, so it does not prove melatonin causes heart disease. Limitations include reliance on medical‑record documentation of prescribed melatonin (over‑the‑counter use may be missed) and the possibility that long‑term melatonin use signals underlying cardiac problems or more severe insomnia rather than being the direct cause. Researchers call for peer‑reviewed study before changing clinical recommendations, and clinicians advise caution interpreting the findings.