New research suggests that people with chronic insomnia who take melatonin for extended periods face a substantially higher risk of developing heart failure within five years. The study, described by its authors as large and preliminary, reported an association corresponding to roughly a 90% increase in risk over that timeframe. The finding is presented as an observational association rather than proof that the supplement causes cardiac problems.
The analysis tracked outcomes over a five-year period and compared those who used melatonin long term with people who did not. While the reported elevation in risk is sizeable, the research team underscored the limits of observational data: confounding factors, differences in underlying health, or other medications could influence the observed relationship. The study does not provide mechanistic evidence tying melatonin directly to heart damage.
The results prompt questions about the safety of prolonged use of a substance commonly taken to manage sleep problems. For people with persistent sleep disorders, including chronic insomnia, the study highlights uncertainty about long-term outcomes associated with nightly supplements. Clinicians and patients may need to weigh potential benefits for sleep against unresolved risks and consider non-pharmacological approaches where appropriate. The research also points to the importance of careful medical review for patients using the supplement continuously.
Further investigation is necessary to determine whether the association holds across different populations and dosing regimens and to explore whether dose, duration or coexisting medical conditions account for the elevated risk. Additional studies — ideally with designs able to address causality and to control for confounders — will be required before firm clinical or regulatory conclusions can be drawn. In the meantime, the study adds a new dimension to the evidence base on long-term melatonin use and its possible cardiovascular implications.
