Overview
- An analysis of more than 130,000 adults with chronic insomnia found those with at least one year of recorded melatonin use had about a 90% higher risk of heart failure, a 3.5-fold higher risk of hospitalization for heart failure, and nearly double the all-cause mortality over five years.
- The results were presented at the American Heart Association Scientific Sessions and have not been published or peer reviewed; the lead author plans to submit the manuscript in early 2026, and experts emphasize this shows association, not causation.
- Key limitations include potential undercounting of over-the-counter use, lack of dosing data, and absent measures of insomnia severity, with experts noting the absolute risk of heart failure remained low in both groups.
- Independent voices suggest underlying sleep disorders such as insomnia or undiagnosed sleep apnoea may explain the observed risks, and they call for randomized controlled trials to test causality.
- Separate European testing by Öko‑Test found many melatonin sprays deviated from label claims, highlighting product variability and differing regulations, while clinical reviews report only modest sleep benefits and encourage CBT‑I and sleep‑hygiene measures over chronic supplement use.