People with chronic insomnia who used melatonin over extended periods faced a roughly 90% higher risk of developing heart failure within five years, according to a large preliminary study reported this week. The findings do not establish that melatonin causes heart problems, but researchers said the association warrants closer scrutiny of a supplement widely assumed to be benign.
The study drew on a large patient cohort and tracked outcomes over a five-year window. Researchers compared heart failure incidence among chronic insomnia patients who used melatonin long-term against those who did not, controlling for established cardiovascular risk factors. The 90% elevated risk remained significant after adjustments for age, sex, body mass index, blood pressure, diabetes status, and other variables.
Melatonin is a hormone produced naturally by the pineal gland that regulates the sleep-wake cycle. It is sold over the counter in the United States and many other countries, typically without prescription, and is used by millions of adults for sleep difficulties, jet lag, and shift-work disruptions. Long-term use has been considered low-risk by much of the public and many clinicians, though rigorous safety data for extended supplementation have been limited.
Study investigators emphasized that the results are preliminary and have not yet been peer-reviewed in a final published form. The research was presented at a scientific meeting, a format that allows findings to be disseminated ahead of full publication but does not permit the same level of independent scrutiny as a peer-reviewed journal article.
Heart failure, the condition at the center of the study, affects an estimated 6.7 million adults in the United States and many more worldwide, according to federal health data. It occurs when the heart muscle cannot pump blood efficiently enough to meet the body’s needs, leading to fatigue, breathlessness, fluid retention, and, in advanced cases, death.
Analysis:
The size of the reported risk increase — 90% — is large enough to demand replication in independent cohorts before altering clinical guidance. Observational studies of this kind cannot rule out confounding: patients prescribed or choosing long-term melatonin may differ from non-users in ways that themselves drive cardiovascular risk, including severity of insomnia, underlying mental health conditions, or concurrent medication use.
The supplement industry has operated with relatively thin post-market safety surveillance for chronic use. Unlike prescription drugs, over-the-counter supplements in the United States are not required to demonstrate long-term safety in randomized trials before reaching consumers. A signal of this magnitude, if confirmed, would expose a regulatory gap that has persisted for decades.
The findings also complicate the common framing of melatonin as a “natural” and therefore inherently safer alternative to pharmaceutical sleep aids such as benzodiazepines or Z-drugs. Natural origin is not a safety certification, and dose-response data for supplemental melatonin have historically been poor.
For patients currently using melatonin long term, the researchers stopped short of recommending discontinuation but urged individuals to discuss extended use with their physicians, particularly those with existing cardiovascular risk factors or established heart disease.
The study’s authors disclosed funding sources and institutional affiliations in the presentation materials; independent replication in a peer-reviewed setting will be the critical next step.
Analysis: Public-health messaging around dietary supplements has consistently lagged behind emerging safety signals because post-market surveillance is voluntary and fragmented. If this association holds in further research, it would represent one of the more substantial cardiovascular risks linked to a widely available over-the-counter product in recent memory.
Analysis: Clinicians treating chronic insomnia may need to weigh the cardiovascular findings against the well-documented harms of untreated sleep disruption, which itself is a recognized risk factor for hypertension, obesity, and heart failure. The emerging evidence argues for more structured sleep-medicine referrals rather than open-ended melatonin continuation, but a full risk-benefit reassessment will require the peer-reviewed dataset.
Sources
Science Daily: https://www.sciencedaily.com/releases/2026/08/260829035228.htm
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Story synopsis gathered from: Science Daily — source
