New AHA Study Links Long-Term Melatonin to Heart Failure Risk — What Athletes Should Know

If you've been reaching for a melatonin gummy before bed, a study presented at the American Heart Association's 2025 Scientific Sessions gives you reason to reconsider. Researchers analyzing data from over 130,000 adults found that long-term melatonin users — taking it for at least 365 days — had an 89% higher hazard of developing heart failure compared to matched controls. They also faced roughly three times the rate of heart failure hospitalizations and double the all-cause mortality over five years.

The study was on people with chronic insomnia, not athletes. But it makes a point that's hard to sidestep: melatonin was never the right tool for training recovery — and this research makes that harder to ignore.

The study, presented by Dr. Ekenedilichukwu Nnadi and colleagues from SUNY Downstate/Kings County Primary Care, used data from the TriNetX Global Research Network — an international database of de-identified medical records covering 130,828 adults diagnosed with chronic insomnia.

Researchers compared 65,414 long-term melatonin users (at least one prescription, taken for 365+ days) against 65,414 matched controls, balanced on demographics, 15 comorbidities, medications, labs, and vitals. Over five years:

• Heart failure incidence: 4.6% in melatonin users vs. 2.7% in controls — an 89% higher hazard ratio

• Heart failure hospitalizations: approximately 3× higher in melatonin users

• All-cause mortality: approximately 2× higher in melatonin users

This is an observational study — association, not causation. The lead author acknowledged that worsening insomnia, depression, or concurrent use of other sleep medications could be confounding factors. But 130,000+ subjects with propensity-matched controls and 15 adjusted comorbidities is a meaningful signal, significant enough for AHA presentation and ACC coverage. The assumption that melatonin is consequence-free long-term no longer holds.

The study population was adults with chronic insomnia averaging 55.7 years old. The cardiovascular risk data doesn't transfer directly to a healthy athlete in their 30s or 40s — don't misread it that way.

But a significant number of athletes have adopted melatonin as a nightly recovery supplement, treating it like magnesium or protein. The logic: it's natural, it helps you sleep, sleep supports recovery. Each link is technically true. The conclusion isn't.

Melatonin is a chronobiotic — a hormone that signals your brain it's dark outside. Its most evidence-supported uses are narrow: jet lag, shift work, delayed sleep phase syndrome. The American Academy of Sleep Medicine's clinical practice guideline advises clinicians against using melatonin to treat sleep onset or sleep maintenance insomnia in adults — the exact application most people are reaching for nightly.

It doesn't do anything specific for the physical rebuilding that happens during deep sleep. That's the part athletes actually need.

The AHA data adds a cardiovascular safety question to an already narrow functional case. If you're using melatonin nightly as a recovery tool, this is reason to reassess — not because the risk data applies to you directly, but because it removes the assumption that long-term daily use is consequence-free.

Recovery sleep isn't just getting enough hours. It's what happens during those hours.

The physiological work your body does while you sleep:

• Growth hormone secretion — peaks during slow-wave (deep) sleep in the first half of the night; critical for muscle repair and tissue adaptation

• Protein synthesis — muscle protein turnover accelerates overnight, particularly during deeper sleep stages

• Nervous system recovery — reduction in cortisol load and restoration of HRV

• Connective tissue repair — collagen synthesis is elevated during sleep, when inflammation is lower and anabolic hormones are higher

Melatonin doesn't meaningfully influence any of these. Here's what does:

Magnesium bisglycinate — not oxide, not citrate. The bisglycinate form supports GABA receptor activity, muscle relaxation, and nervous system downregulation. Published research at 250mg shows measurable improvements in sleep quality and efficiency.

L-theanine at 200mg promotes alpha brain wave activity — the calm state that supports smooth sleep onset without next-day grogginess. It also attenuates stress-induced cortisol response, which matters on high-load training days.

GABA at 300mg supports sleep onset speed and slow-wave sleep depth — the stage where growth hormone is released and the most significant physical repair occurs.

Hydrolyzed collagen peptides — this is what makes recovery sleep supplementation different for athletes. 10g of hydrolyzed collagen provides approximately 3g of glycine, an amino acid with published evidence for improving sleep quality, reducing sleep latency, and decreasing next-day fatigue. It also plays a direct structural role in connective tissue repair overnight. No other supplement category meaningfully addresses this.

Melatonin is one of the best-selling supplements in the United States. Most people take it because it seems natural and low-stakes. The AHA 2025 data doesn't prove it causes heart failure — but it disrupts the assumption that long-term daily use is consequence-free.

For athletes, the more fundamental issue: melatonin was solving for the wrong problem. Your body doesn't need a stronger darkness signal. It needs the conditions for deep, restorative sleep — and the raw materials to rebuild connective tissue, clear metabolic waste, and reset the nervous system that absorbed today's training load.

Sleep is an active rebuilding process. The supplement stack should reflect that.

The 2025 AHA study found an 89% higher risk of heart failure in adults with chronic insomnia taking melatonin for 365+ days. The study population was older (avg. age 55.7) and clinically diagnosed with insomnia — so the cardiovascular findings don't apply directly to a healthy, fit adult. That said, the data challenges the assumption that nightly melatonin is consequence-free. More importantly, melatonin doesn't address the recovery mechanisms that matter after training — muscle repair, GH secretion, connective tissue rebuilding. If it's in your stack as a recovery tool, it's not earning its spot.

Fair point — the cardiovascular risk data isn't a direct warning for healthy athletes. But it's a legitimate safety signal that challenges the assumption melatonin is harmless long-term. And more importantly: athletes frequently use melatonin for reasons the evidence doesn't support. It signals darkness — it doesn't deepen sleep architecture, support GH secretion, or rebuild connective tissue. The study makes a weak functional case even weaker.

The ingredients with the strongest evidence for athletic sleep recovery are: magnesium bisglycinate (sleep efficiency, muscle relaxation, GABA support), L-theanine (alpha wave activity, stress cortisol attenuation), GABA (slow-wave sleep depth and onset speed), and glycine — most efficiently delivered through hydrolyzed collagen peptides. 10g collagen provides ~3g glycine, shown to improve sleep quality, reduce sleep latency, and decrease next-day fatigue. It also supports connective tissue repair overnight. These address what your body actually does while you sleep.

The AHA study defined long-term use as at least 365 continuous days of exposure — the threshold where the cardiovascular associations became statistically significant. Occasional use for jet lag, time zone shifts, or acute sleep disruption was not the study population. The concern is nightly, habitual use over a year or more.

Yes. Melatonin has strong evidence as a chronobiotic for resetting your circadian clock when crossing time zones, especially three or more eastward. Used strategically for jet lag, it's doing what it was designed to do. Nightly use as a general sleep and recovery supplement is a different application — and one the evidence, including this new AHA data, doesn't support.

No. Rest & Recover was formulated specifically without melatonin, CBD, or L-tryptophan. It contains 10g hydrolyzed collagen (~3g glycine), 300mg GABA, 250mg magnesium bisglycinate, and 200mg L-theanine — a stack built for sleep quality and overnight physical recovery. Informed Sport certified, made in the USA.