Lead: A preliminary, non–peer-reviewed analysis presented at an American Heart Association meeting finds a higher five‑year rate of heart failure among adults with insomnia who had records of long‑term melatonin prescriptions compared with those without such prescriptions. The research used international electronic health records and reported 4.6% incidence in chronic melatonin users versus 2.7% in non‑users over five years. Investigators from SUNY Downstate characterized the results as an indicator for more study, while cardiologists emphasize the limits of observational data and advise patients to consult their doctors rather than stop melatonin abruptly.
Key takeaways
- The study analyzed international electronic health records of adults diagnosed with insomnia and with a melatonin prescription consistent with at least one year of use.
- Over five years, 4.6% of patients with chronic melatonin prescriptions developed heart failure versus 2.7% of insomnia patients without melatonin records (an absolute difference of 1.9 percentage points).
- The analysis was presented at an American Heart Association meeting and has not completed peer review, limiting conclusions about causality.
- The study did not report melatonin dosages and may miss over‑the‑counter use in countries where melatonin is available without a prescription, including the U.S.
- Experts quoted (Emory and Northwestern) caution against alarm and recommend doctors discuss sleep strategies and individual risk with patients.
- U.S. dietary supplements are not subject to premarket approval, so product content and dosing can vary across brands and countries.
Background
Melatonin is an endogenous hormone that helps regulate the sleep–wake cycle; levels normally rise after dark and promote drowsiness. In many countries people also take laboratory‑made melatonin to ease insomnia, shift work, jet lag or circadian rhythm problems. Regulatory frameworks differ: several nations require a prescription for melatonin, while in the United States it is widely sold over the counter as a dietary supplement.
Sleep deprivation and fragmented sleep are established risk factors for cardiovascular disease, including heart failure, so clinicians have long weighed the risks and benefits of sleep aids. Observational health records can reveal associations across large populations but cannot by themselves prove that one factor causes another, because unmeasured factors linked to both insomnia and heart disease may confound results.
Main event
The SUNY Downstate team reported their analysis at the American Heart Association meeting, describing an elevated five‑year heart‑failure incidence among adults whose records indicated they had a melatonin prescription consistent with at least a year’s use. The researchers extracted diagnostic and prescription data from several countries’ electronic health records to compare outcomes in people diagnosed with insomnia who did and did not have melatonin prescriptions.
Across the cohort, 4.6% of the chronic‑prescription group developed heart failure within five years, compared with 2.7% among those without melatonin prescriptions—a 1.9 percentage‑point absolute increase and about a 70% relative increase. The presenters framed this as a signal warranting further investigation rather than definitive evidence of harm.
Investigators acknowledged limitations in the dataset: the study did not capture over‑the‑counter usage where that occurs, did not record product dosages, and could not fully account for severity of insomnia or other cardiovascular risk factors that might differ between groups. These caveats were central to experts’ cautions about interpreting the results.
Analysis & implications
First, the distinction between association and causation is critical. Observational designs can identify correlations but are vulnerable to confounding. For example, patients using long‑term melatonin may have more severe, chronic sleep disorders or comorbidities that independently increase heart‑failure risk.
Second, the absence of dosing information and the variability in supplement formulations complicate any attempt to generalize findings to over‑the‑counter melatonin commonly used in the U.S. Without standardized dosing or product testing, one registry’s ‘‘prescription’’ cohort may differ substantially from consumers taking variable preparations.
Third, the reported absolute risk difference—1.9 percentage points over five years—should be interpreted alongside baseline risk. For an individual with low cardiovascular risk, the absolute increase is small; for higher‑risk patients, even modest increases in incidence may be clinically meaningful. This nuance argues for individualized discussions between patients and clinicians, rather than population‑level mandates to stop use.
Comparison & data
| Group | 5‑year heart‑failure incidence |
|---|---|
| Insomnia with ≥1 year melatonin prescription | 4.6% |
| Insomnia without melatonin prescription | 2.7% |
That table summarizes the headline numbers presented. The dataset’s international composition and the study’s observational nature both affect how broadly the figures can be applied to different health systems and consumer behaviors. Analysts caution that unmeasured variables—severity of underlying sleep disorder, comorbid conditions, concomitant medications—could explain part or all of the observed gap.
Reactions & quotes
“We should not raise the alarm and tell patients to stop taking all their melatonin,”
Dr. Pratik Sandesara, interventional cardiologist, Emory Healthcare
Sandesara, not involved in the research, emphasized clinical context and advised that clinicians guide patients on sleep strategies and short‑term melatonin use where appropriate.
“The study does not prove long‑term melatonin causes heart failure, and U.S. over‑the‑counter use may not be captured in this dataset,”
Dr. Clyde Yancy, chief of cardiology, Northwestern University
Yancy highlighted the limits of international prescription records for countries where melatonin is available without a prescription and noted the lack of dosage information in the analysis.
Unconfirmed
- Whether melatonin itself causes the higher heart‑failure incidence is unproven; the study shows association, not causation.
- The degree to which unrecorded over‑the‑counter melatonin use in the U.S. affected group assignment is unknown.
- Dosage and product formulation for the recorded users were not reported, leaving dosing‑related risk unanswered.
- Potential confounders such as insomnia severity, lifestyle factors or other medications may partly explain the observed differences.
Bottom line
The reported 4.6% versus 2.7% five‑year heart‑failure rates merit attention as a signal that should prompt deeper, controlled research rather than immediate clinical alarm. For individuals, the absolute increase—1.9 percentage points—should be weighed against baseline cardiovascular risk and the reason melatonin is being used.
Clinicians and patients are advised to discuss sleep problems and treatment options together. Short‑term melatonin for specific indications (for example, jet lag) remains standard practice in many settings, while long‑term use should prompt periodic reassessment, attention to sleep hygiene, and consideration of underlying conditions that may drive both insomnia and cardiovascular risk.
Sources
- The Associated Press — original coverage and corrected item (news)
- American Heart Association — conference/meeting of record (professional organization)
- SUNY Downstate Health Sciences University — research institution (academic)
- Emory Healthcare — clinical institution (commenting clinicians)
- Northwestern Medicine — clinical institution (commenting clinicians)