The natural sleep aid you’ve trusted for years might be silently damaging your heart.
Quick Take
- A major study of 130,000 insomnia patients found long-term melatonin users faced nearly double the risk of heart failure and death compared to non-users
- The research, presented at the American Heart Association’s 2025 Scientific Sessions, challenges the widespread belief that melatonin is a harmless supplement
- Experts emphasize the study shows association, not causation, and call for rigorous follow-up research before changing clinical practice
- Millions of Americans regularly use melatonin, making these findings potentially significant for public health and supplement regulation
The Study That Changed Everything About Sleep Supplements
A multinational research team analyzing health records from over 130,000 adults with chronic insomnia discovered something alarming: those who took melatonin supplements for at least one year showed a 89 percent higher risk of developing heart failure.
The association grew even more troubling when researchers examined hospitalization rates for heart failure, which were roughly three and a half times higher in long-term melatonin users. All-cause mortality over the five-year study period was also significantly elevated at 109 percent higher risk. These numbers represent one of the largest examinations of melatonin’s long-term cardiovascular effects ever conducted.
Why This Matters Now
Melatonin has occupied a unique space in American medicine since the 1990s. It’s natural, available without prescription, affordable, and widely promoted as a safe alternative to habit-forming sleep medications. During the COVID-19 pandemic, melatonin use exploded as sleep problems intensified and people sought gentler solutions.
The supplement industry has capitalized on this perception, marketing melatonin as virtually risk-free. Yet until this November 2025 study presentation at the American Heart Association’s Scientific Sessions, robust long-term safety data simply didn’t exist. Most research focused on short-term use, leaving a critical knowledge gap about what happens when millions of people take melatonin night after night for years.
Understanding the Numbers Behind the Headlines
The raw statistics are striking. Among melatonin users in the study, 4.6 percent developed heart failure compared to 2.7 percent of non-users. For hospitalizations related to heart failure, the gap widened dramatically: 19 percent of long-term melatonin users versus 6.6 percent of non-users. All-cause mortality showed 7.8 percent of melatonin users died during the study period against 4.3 percent of non-users.
Researchers calculated these associations as hazard ratios, statistical measures that account for various factors. The data came from TriNetX Global Research Network, a massive international health database spanning multiple countries and healthcare systems, lending credibility to the findings’ scope and diversity.
The Critical Limitation Everyone’s Discussing
Here’s where the story becomes more complex. This was an observational study, meaning researchers watched what happened to people who already chose to take melatonin versus those who didn’t. They didn’t randomly assign people to melatonin or placebo groups. This distinction matters enormously. Association is not causation. People with severe insomnia who turn to melatonin might already have underlying cardiovascular vulnerabilities. Chronic insomnia itself is independently linked to heart disease, heart failure, and early death. Researchers cannot definitively say melatonin caused the problems; they can only say the two conditions occurred together more often than expected. This ambiguity is why cardiologists and sleep specialists are urging caution before changing how they recommend melatonin to patients.
What Sleep Doctors Are Saying
Sleep medicine specialists acknowledge the study’s significance while emphasizing its preliminary nature. The findings highlight the lack of understanding about what long-term melatonin does to the cardiovascular system, raising legitimate safety concerns that warrant investigation. However, experts stress that the study hasn’t undergone peer review yet, and the observational design prevents definitive conclusions about melatonin’s direct effects. Many point out that insomnia patients face elevated heart failure risk regardless of treatment choice. The question becomes whether melatonin worsens that existing risk or merely correlates with it. Most experts agree: we need rigorous, randomized controlled trials where researchers randomly assign participants to melatonin or placebo and follow them over years, measuring cardiovascular outcomes carefully.
The Industry Response and What It Means
The Council for Responsible Nutrition, representing supplement manufacturers, responded quickly to the study’s presentation. Industry representatives urged stakeholders to interpret the findings cautiously, emphasizing its observational nature and preliminary status. They noted that jumping to conclusions could unnecessarily alarm millions of people using melatonin safely. This response reflects legitimate industry concerns about potential regulatory action or public backlash. Yet it also highlights the tension between protecting consumer interests and protecting business interests. Regulatory agencies like the FDA will likely scrutinize these findings closely, potentially requiring updated labeling or further investigation before making any policy changes.
What This Means for Your Medicine Cabinet
For the millions of Americans currently taking melatonin, this study doesn’t mandate immediate action. Experts recommend consulting with your doctor before making changes to your sleep regimen. If you’re using melatonin short-term for occasional sleep issues, the risk profile appears different from long-term chronic use. If you have existing heart disease, heart failure risk factors, or chronic insomnia requiring ongoing melatonin use, a conversation with your physician becomes essential. Your doctor can weigh your individual cardiovascular risk factors against the benefits of melatonin versus exploring alternative sleep interventions. Behavioral approaches like sleep hygiene improvements, cognitive behavioral therapy for insomnia, or other medications might offer safer options depending on your specific situation.
The Bigger Picture for Supplement Safety
This melatonin study illuminates a broader problem: dietary supplements in America operate under different regulatory frameworks than prescription medications. The FDA doesn’t require the same rigorous testing before supplements hit store shelves. Long-term safety data often lags years behind widespread consumer use. Melatonin represents just one example. This research may catalyze more thorough investigation of other popular supplements’ long-term effects. It also underscores why observational studies, while valuable for generating hypotheses and raising red flags, cannot replace gold-standard randomized trials for establishing causation. The scientific community’s next move will be crucial: designing prospective studies that can definitively answer whether melatonin itself causes cardiovascular harm or whether the association reflects underlying health differences between users and non-users.
Sources:
Parkview: A New Warning About Melatonin and Heart Health
American College of Cardiology: Melatonin Study Presentation
University of Rochester Medical Center: Can Melatonin Cause Heart Failure
Baptist Health: Long-Term Use of Sleep Supplement Melatonin Linked to Potential Heart Risks
American Heart Association Newsroom: Long-Term Use of Melatonin Supplements
TIME: Melatonin and Heart Failure Sleep Supplement
Council for Responsible Nutrition: Response to Melatonin Study
