Melatonin is widely used as a sleep aid, with its regulatory status varying between countries. That made a conference abstract presented at the American Heart Association’s 2025 Scientific Sessions particularly alarming. The researchers reported that adults with insomnia whose medical records indicated at least a year of melatonin use had an 89 percent higher hazard of developing heart failure over the following five years.
The abstract analyzed 130,828 adults with insomnia using electronic health records from the TriNetX Global Research Network. Half had at least 365 days of recorded melatonin exposure, while the other half had no melatonin exposure recorded. Heart failure occurred in 4.6 percent of the melatonin group compared with 2.7 percent of the comparison group. The researchers also reported higher rates of heart failure hospitalization and death from any cause among people with recorded melatonin use.
The numbers are striking, but because the analysis was observational, they cannot establish that melatonin caused the higher rate of heart failure. The findings also raise questions about how accurately the recorded exposure reflects actual melatonin use and whether the two groups differed in ways that the researchers could not account for.
What the abstract could not tell us
The researchers matched the two groups across numerous characteristics, including medical conditions, medications, laboratory results, vital signs, and health care use. This can reduce differences between the groups, but it cannot account for information that was never recorded.
The analysis identified melatonin exposure through prescription and other recorded data. That means it could not show whether participants actually took the melatonin, and the abstract does not give enough detail about dose or how consistently it was used.
The TriNetX database uses health records from different countries, where melatonin is not accessed in the same way. In the United States, it is available without a prescription, while in the United Kingdom it is prescription-only. A person taking melatonin in the U.S. could therefore have no prescription record at all, meaning that some actual users may have been classified as having no recorded exposure.
All of the participants had insomnia, which is itself associated with cardiovascular problems, including heart failure.
Insomnia already has cardiovascular consequences
Chronic insomnia can affect the cardiovascular system in several ways. Persistent sleep disruption can keep the body in a state of heightened stress, with increased sympathetic nervous system activity, higher blood pressure, and changes in the hormones involved in the stress response.
Over time, these effects can place additional strain on the heart and blood vessels and contribute to cardiovascular disease, including heart failure. The longer sleep problems persist, the more relevant this cumulative effect may become.
Cardiovascular disease can also interfere with sleep. Symptoms and physiological changes associated with cardiovascular problems can disrupt normal sleep, sometimes before the condition has been diagnosed. This means that insomnia can precede cardiovascular disease, follow it, or develop alongside it.
The finding does not fit neatly with other cardiovascular research
A 2025 systematic review and meta-analysis examined four randomized trials involving patients with heart failure. Although the evidence was limited, the authors reported improvements in quality of life, NT-proBNP, and some measures of cardiac function, and concluded that melatonin might have a role as an adjunctive treatment for heart failure.
An even broader systematic review published in 2026 included 14 randomized trials and 1,027 participants with cardiovascular disease. Melatonin was associated with a significant improvement in the change in left ventricular ejection fraction, particularly among patients undergoing coronary artery bypass surgery. The results were not consistently positive across all cardiovascular outcomes, however, and the authors emphasized substantial differences between the trials.
The results were encouraging, particularly because some of the trials involved people who already had heart failure. Although the evidence is not yet definitive, the findings raise the possibility that melatonin could have beneficial cardiovascular effects, which is difficult to reconcile with the idea that it substantially increases the risk of heart failure.
What should melatonin users make of this?
The AHA abstract does not provide enough evidence to conclude that melatonin causes heart failure. However, its findings raise a legitimate question about long-term use that deserves further investigation, particularly in research that can measure dose, duration, and actual exposure more accurately.
For people taking melatonin, the findings are also a reason to pay attention to the insomnia being treated. Persistent insomnia has itself been associated with cardiovascular problems, so treating sleep difficulties should not be reduced to taking a sleep aid. If insomnia continues over time, it may be worth discussing other approaches with a health professional rather than relying indefinitely on melatonin.
Clinicians may also want to ask specifically about melatonin when reviewing a patient’s medications and supplements. People do not always mention it because they may think of it as a supplement rather than a medication, and its use may therefore be absent from the medical record.
For now, the 2025 abstract is best viewed as a signal that warrants further research, not as evidence that melatonin increases the risk of heart failure. The available cardiovascular research, including randomized trials in people with heart disease, does not point in a single direction of harm. That makes the question of long-term melatonin use worth investigating without turning one preliminary finding into a reason for alarm.