A preliminary study presented at the American Heart Association conference in New Orleans, United States, analyzed medical records of more than 130,000 adults with chronic insomnia. Researchers found that using melatonin for at least one year is associated with a 90% higher risk of developing heart failure over five years.
The research, led by Ekenedilichukwu Nnadi, a resident in internal medicine at SUNY Downstate in New York, compared groups of users and non-users of the supplement, adjusting for factors such as age, sex and pre-existing conditions.
The results indicate that participants in the melatonin group had a 4.6% rate of heart failure diagnosis, compared to 2.7% in non-users. Experts emphasize that the analysis only shows correlation, without proving direct causality.
Research methodology and main findings
The data came from global electronic records on the TriNetX platform, covering patients with an average age of 56 years diagnosed with insomnia.
Researchers excluded individuals with a prior history of heart failure or use of other sleep aids, such as benzodiazepines, to isolate the effect of melatonin.
- UsageMelatonin levels: 90% more risk of heart failure; 3.5 times greater chance of hospitalization (19% vs. 6.6%); almost twice as likely to die from any cause (7.8% vs. 4.3%).
- Non-users: Lower basal rates, but still relevant for monitoring in chronic insomnia.
The analysis adjusted variables such as body mass index, blood pressure and use of cardiovascular medications, maintaining the significant association.
Limitations that question causality
The study relies on registered prescriptions, which may underestimate over-the-counter use common in countries such as the United States and Brazil.
There is a lack of details about dosages and severity of insomnia, factors that influence heart risks, according to experts such as Phyllis Zee, from Northwestern Medicine.
Severe insomnia or underlying conditions such as undiagnosed sleep apnea may explain the results, acting as confounders.
Doctors like Sujay Kansagra of Duke Health point out that the absolute risk remains low in both groups, suggesting caution without panic.
What is heart failure and its prevalence
Heart failure occurs when the heart does not pump enough blood to supply organs with oxygen, affecting 6.7 million adults in the United States, according to statistics from the American Heart Association in 2025.
In Brazil,Data from the Ministry of Health indicate that the condition accounts for around 10% of annual cardiovascular hospital admissions, with an increase in populations with sleep disorders.
Factors such as hypertension, diabetes and chronic insomnia worsen the condition, highlighting the need for integrated approaches to heart health and sleep.
The condition progresses silently in many cases, with symptoms such as fatigue and shortness of breath appearing late, which reinforces the importance of regular assessments in supplement users.
Safe alternatives to treat insomnia
Cognitive behavioral therapies for insomnia represent the first line of treatment, with proven efficacy in randomized studies to improve sleep patterns without medication risks.
Establishing nighttime routines, such as avoiding caffeine after noon and maintaining a fixed sleep schedule, reduces symptoms in up to 70% of cases, according to guidelines from the American Academy of Sleep Medicine.
Moderate daily exercise and exposure to natural light during the day help regulate circadian rhythms, reducing dependence on supplements.
In specific situations, such as jet lag, low doses of melatonin can help, but always under medical supervision to avoid interactions.
Melatonin regulation in Brazil
Since 2021, Anvisa classifies melatonin as a food supplement, allowing sale without a prescription in pharmacies and specialized stores.
The agency recommends dosages of up to 0.21 mg for adults, but the market offers higher variations, which raises concerns about self-medication.
Monitoring of adverse effects is mandatory, with annual reports to Anvisa, but experts are calling for more local studies on cardiovascular impacts in Brazilian populations.
Use should prioritize professional guidance, especially for those with a family history of heart disease or persistent insomnia.
Future research perspectives
Randomized controlled clinical trials are essential for testing causality, assigning melatonin or placebo to groups and measuring long-term cardiac outcomes.
Nnadi plans to submit the work for publication in 2026, aiming to expand the sample and include variable dosages.
Contradictory previous studies, such as a March 2025 analysis that showed benefits in patients with heart failure, demand reconciliation of evidence.
The research could influence global guidelines on supplements, promoting a balance between sleep benefits and cardiovascular safety.
