“A large retrospective study of over 130,000 adults with chronic insomnia found that long-term melatonin use (≥1 year) was associated with an 89% higher risk of heart failure, threefold higher heart-failure-related hospitalizations, and double the all-cause mortality compared to non-users over a 5-year period." Accompanying image text:…”
Plain restatementA conference abstract using electronic health record data from 130,828 adults with an insomnia diagnosis reported that those with at least one year of recorded melatonin exposure had higher observed rates of incident heart failure, heart failure hospitalization, and death from any cause over five years than a matched group with no recorded melatonin exposure.
This claim accurately reports the numbers from a real study. Researchers analyzed health records for 130,828 adults with insomnia and found that those with at least a year of recorded melatonin use had an 89 percent higher hazard of heart failure, higher heart failure hospitalization rates, and about double the death rate over five years compared with matched non-users. However, the framing overstates it. The actual difference in heart failure was 4.6 percent versus 2.7 percent, a gap of under 2 percentage points, which is not a "massive" risk. It was also a conference abstract, not a peer-reviewed published paper, and the American Heart Association itself labeled the findings preliminary. A major flaw experts pointed out is that melatonin is sold over the counter in the United States, so many people in the "non-user" comparison group may have been taking melatonin without it showing up in their records. Randomized trials, which are stronger evidence, have generally found neutral or favorable cardiac effects from melatonin, so this result contradicts the existing evidence base rather than confirming it. It is a signal worth further research, not proof that melatonin damages the heart.
A [drifted from the evidence:] large retrospective study of over 130,000 adults with [drifted from the evidence:] chronic insomnia [drifted from the evidence:] found that [drifted from the evidence:] long-term melatonin use (≥1 year) was associated with [drifted from the evidence:] an 89% higher [drifted from the evidence:] risk of heart failure, [drifted from the evidence:] threefold higher heart-failure-related hospitalizations, and double the all-cause mortality compared to non-users over a 5-year period." Accompanying image text: "Melatonin use linked to a massive increased risk of heart failure" [drifted from the evidence:] Accompanying caption: "A [drifted from the evidence:] major study has linked melatonin [drifted from the evidence:] use to a 90% higher risk of heart failure, raising urgent safety questions about the 'natural' sleep aid.
A [added by the neutral restatement:] conference abstract using electronic health record data from 130,828 adults with [added by the neutral restatement:] an insomnia [added by the neutral restatement:] diagnosis reported that [added by the neutral restatement:] those with [added by the neutral restatement:] at least one year of recorded melatonin exposure had higher [added by the neutral restatement:] observed rates of [added by the neutral restatement:] incident heart failure, heart failure [added by the neutral restatement:] hospitalization, and death from any cause over five years than a [added by the neutral restatement:] matched group with no recorded melatonin [added by the neutral restatement:] exposure.
Red-tinted words in the claim drifted from the evidence. Green-tinted words are what a neutral restatement needs.
The trace / claim to source
- The study exists, is correctly attributed to the American Heart Association's 2025 Scientific Sessions, and was published as an abstract in a Circulation supplement.
- The sample size figure (over 130,000 adults with an insomnia diagnosis) is correct: 130,828, matched 65,414 to 65,414.
- The 89% figure is correct and correctly labeled as a hazard, matching HR 1.89.
- The "threefold higher heart-failure-related hospitalizations" figure matches HR 3.44.
- The "double the all-cause mortality" figure matches HR 2.09.
- The five-year follow-up period is correct.
- The claim correctly uses "was associated with" rather than causal language.
- The post's own body text correctly discloses that this is observational, shows association not causation, and could not control for dosage, insomnia severity, or mental health conditions. These caveats match what the AHA and independent experts said.
- Exaggeration (image headline): "a massive increased risk" overstates the finding. The absolute risk difference was 1.9 percentage points over five years (4.6% versus 2.7%). An 89% relative increase on a small baseline is not a "massive" absolute risk. The claim body reports the relative figure without the absolute figure, which is the single most important missing number for a reader assessing personal risk.
- Omitted qualifier (source citation): the post's source line, "American Heart Association. (2025). ... Circulation," presents this as a Circulation journal article. It is a non-peer-reviewed conference abstract in a meeting supplement. The AHA explicitly labels such abstracts preliminary. The post's caption calls it "a major study" without noting it has not been peer-reviewed or published as a full manuscript.
- Exposure misclassification not disclosed: the claim says "melatonin use," but exposure was defined by prescription records. Because melatonin is sold over the counter in the US, an unknown share of the "non-user" control group likely used melatonin. This would be expected to bias results, and the post does not mention it despite listing other limitations.
- Confounding by indication not disclosed: people who are prescribed melatonin for a year or more plausibly have more severe or more refractory insomnia than those who are not, and insomnia severity is itself linked to cardiovascular risk. The post mentions insomnia severity as an uncontrolled factor but frames it as a minor caveat rather than a central alternative explanation.
- Omitted contradictory evidence: randomized trial evidence points in the opposite direction on cardiac function, and the post presents the abstract as if it stands alone.
- Whether melatonin causes any of these outcomes. The design cannot answer this, and no randomized long-term cardiovascular safety trial of melatonin exists.
- Whether the abstract has since been published as a full peer-reviewed manuscript. My searches did not locate a full publication, only the supplement abstract and subsequent commentary.
- The reliability of the heart failure hospitalization endpoint, given the internal inconsistency described above. Full methods are not available in an abstract.
- Dose, formulation, and adherence. None were captured.
- The proportion of controls who were actually unrecorded over-the-counter melatonin users. This is explicitly unknown.
The abstract exists and the numbers in the claim are reported correctly. The abstract states that during five-year follow-up, incident heart failure occurred in 3,021 melatonin users (4.6%) versus 1,797 controls (2.7%), an HR of 1.89 (95% CI 1.78 to 2.00) with an absolute risk difference of 1.9%; heart failure related hospitalization occurred in 12,411 users (19.0%) and 4,309 controls (6.6%), HR 3.44; and all-cause mortality was higher in melatonin users (7.8% vs 4.3%), HR 2.09. Results were consistent in a sensitivity analysis requiring two or more melatonin fills at least 90 days apart (HR for HF 1.82). The authors concluded that in a large multinational real-world cohort matched on more than 40 baseline variables, long-term melatonin supplementation in insomnia was associated with an 89% higher hazard of incident heart failure, a threefold increase in HF-related hospitalizations, and a doubling of all-cause mortality over five years. Critically, the AHA itself attached a preliminary-evidence warning: the study featured in the release is a research abstract, abstracts presented at AHA scientific meetings are not peer-reviewed, and findings are considered preliminary until published as full manuscripts in a peer-reviewed journal.
Complete reasoning
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