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December 10, 2025
Birgitta Dunckel
A new study on the long-term use of melatonin shows an increased risk of heart failure. What does this mean for heart health? All the facts about the sleep aid
With
Prof. Dr. Dr. Ferdinand Vogt
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Melatonin is considered one of the world's most popular natural sleep aids. The hormone, which regulates the sleep-wake cycle, comes in numerous forms of administration. As tablets and capsules, sprays and dragées, as gummy bears and as powder. The active ingredient is used to treat sleep disorders (insomnia).
Now new data is causing a stir: A new large-scale study, presented at the American Heart Association (AHA) Scientific Sessions 2025, questions the safety of the sleep hormone. The study shows clear evidence that long-term use of melatonin could increase the risk of heart failure and other cardiovascular problems.
In heart failure, the heart's pumping ability is impaired. The heart is therefore no longer able to supply the body, and thus organs like the brain, muscles, or kidneys, with sufficient blood and oxygen.
Until now, melatonin was considered rather positive for heart health. It was said that the body's own hormone, thanks to its antioxidant properties, lowers blood pressure, protects blood vessels, and regulates heart rate. However, the new data from the USA now question this thesis.
The presentation study led by Dr. Ekenedilichukwu Nnadi, chief resident of internal medicine at SUNY Downstate/Kings County Primary Care in New York, analyzed health data from 130,828 adults with chronic insomnia.
About half of the subjects regularly took melatonin for at least 12 months. Researchers excluded individuals with existing heart failure. Likewise, people who used other sleep aids besides melatonin.
Both groups – melatonin users and non-users – were matched based on more than 40 factors (including age, gender, comorbidities, blood pressure, BMI, and medication). Over five years, heart failure, hospitalizations, and mortality were examined.
• 90% higher risk of heart failure with long-term use.
• Hospital admissions due to heart failure:
o 19% in the melatonin group
o 6.6% in the control group
• Mortality almost twice as high (7.8% vs. 4.3%).
These data suggest that regular melatonin use is not as harmless as many consumers believe.
Prof. Dr. Ferdinand Vogt, Senior Consultant in Cardiac Surgery at Artemed Klinikum München Süd, however, says: "In principle, one must always ask whether such effects occur causally or coincidentally. Any long-term use of medication should be questioned and accompanied by a doctor. Regarding the "safety" of melatonin, I think of Paracelsus, who said: 'If something has no side effects, then it probably has no main effects either!'"
Despite the size of the investigation, experts emphasize: The study shows correlations but no causal cause. Exactly how melatonin could promote the development of heart failure is open. A direct causal link has not been demonstrated – the study is observational, not experimental.
The study does not know:
To address such reporting for patients, it is always helpful in cases of long-term sleep disorders and necessary medication to consult a doctor. Visiting a sleep laboratory and a thorough internal/cardiological examination are indispensable here.
Also important: Insomnia itself increases the heart risk. People with severe sleep disorders could automatically have a higher baseline risk — regardless of the melatonin taken. The international database used contains very heterogeneous health data. This makes clear statements about specific risk groups difficult. As the results have only been presented, not published, independent validation by other researchers is lacking.
In the short term, it can help — in the long term, it should be medically supervised. People with heart conditions should be particularly careful. Melatonin should therefore not be taken lightly or continuously without medical supervision.
Randomized clinical trials now need to clarify:
