The melatonin heart failure headline comes from an American Heart Association conference abstract (November 2025): among 65,414 adults with insomnia who had used melatonin for at least a year, 4.6% were diagnosed with heart failure within 5 years, against 2.7% of 65,414 matched adults who had not (hazard ratio 1.89). It is an observational health-record comparison that was not peer reviewed when presented, and it cannot show that melatonin caused anything: people who take melatonin differ from those who do not in exactly the ways that also raise heart risk. A 2026 NHANES analysis found no significant link between recent melatonin use and heart failure, and also said that this does not prove long-term safety. If you take melatonin and have a heart condition or take heart medicines, the useful step is to tell your prescriber or pharmacist.
The headline reached two kinds of readers. One has taken melatonin most nights for a couple of years and just saw the news. The other is a relative who saw the same headline and called. Both deserve the actual numbers, and the actual limits.
In November 2025 a conference abstract reported melatonin linked to heart failure: people with insomnia who used it long term were diagnosed with heart failure more often. Below is what it measured, why it cannot show cause, what a 2026 reality check using a national survey found, and what that leaves for someone who takes melatonin.
What does the melatonin heart failure abstract actually say?
The abstract is titled "Effect of Long-term Melatonin Supplementation on Incidence of Heart Failure in Patients with Insomnia" and was published in the Circulation conference supplement for the American Heart Association Scientific Sessions 2025. The authors searched the TriNetX Global Research Network, a pool of electronic health records, for adults with an insomnia diagnosis. The melatonin group needed at least one melatonin prescription and at least 365 days of exposure. The comparison group had no melatonin. People who already had heart failure or who took other prescription sleep drugs were left out.
After matching one-to-one on demographics, 15 other conditions, heart and metabolism drugs, lab values, vitals and health-care use, each group held 65,414 people. Over 5 years, heart failure was newly diagnosed in 3,021 melatonin users (4.6%) and in 1,797 comparison patients (2.7%), a hazard ratio of 1.89 (95% CI 1.78 to 2.00) and an absolute difference of 1.9 percentage points. Hospitalization for heart failure was recorded in 19.0% of users against 6.6% of controls (HR 3.44), and death from any cause in 7.8% against 4.3% (HR 2.09). Requiring at least two melatonin fills 90 days apart gave a heart failure HR of 1.82.
Nnadi et al. Abstract 4371606: Effect of Long-term Melatonin Supplementation on Incidence of Heart Failure in Patients with Insomnia. Circulation 2025 (AHA Scientific Sessions supplement). DOI 10.1161/circ.152.suppl_3.4371606
The authors' own wording is careful: melatonin was "associated with" these outcomes, and the findings "underscore the need for randomized trials". The abstract also leaves one thing open. More than four times as many users were hospitalized for heart failure (12,411) as were newly diagnosed with it (3,021), and the abstract does not say how those two counts relate. That is a reason to wait for the full paper before leaning on the hospitalization figure.
Why a link in health records is not a cause
A trial hands melatonin to some people at random. A health-record comparison cannot, so it compares people who ended up taking melatonin with people who did not, and those groups were different before the first pill. Matching on more than 40 recorded variables helps, but it can only balance what the records contain.
A commentary from Vanderbilt University published in 2026 in Open Heart lists the weak points of this design. Melatonin use reflects why a person is taking it: insomnia, stress, depression or anxiety symptoms, medicines that disturb sleep. Those reasons are tied to heart risk and to how often someone sees a doctor (confounding by indication). Reverse causality is plausible too, because early, undiagnosed heart trouble can worsen sleep and lead someone to try melatonin, so the supplement appears before the diagnosis without having caused it. Melatonin bought over the counter is often missing from records, and dose, formulation and timing are rarely known. The commentary cites independent analyses showing large gaps between labelled and measured melatonin content in supplements, which muddies any dose question.
There is a quieter problem as well. The abstract does not list insomnia severity among the matched variables. The commentary notes that insomnia symptoms have been linked to later heart failure in prospective cohorts, and that depression and anxiety symptoms push people toward melatonin. If severity drives both melatonin use and heart failure, the gap between the two groups can appear without the melatonin doing anything.
Khan B, Lima BB. Melatonin and cardiovascular risk: an NHANES reality check after recent heart failure concerns. Open Heart 2026. PMID 42167796
What a second look at survey data found
The Open Heart authors asked a related question in a different dataset: NHANES, the US National Health and Nutrition Examination Survey, in adults aged 20 and older between 1999 and 2018. They counted anyone who reported melatonin use in the past 30 days (267 users against 50,662 non-users, unweighted) and looked at self-reported cardiovascular disease and heart failure. Their first finding is the baseline gap. Melatonin users reported sleep disturbance far more often than non-users (57.9% against 20.5%), and depression too (13.3% against 5.5%), and they were older with more high blood pressure (40.6% against 30.6%).
After adjusting for age, sex, race and ethnicity, body mass index, smoking, high blood pressure and diabetes, recent melatonin use was not significantly linked to cardiovascular disease overall (odds ratio 0.90, 95% CI 0.58 to 1.40) or to heart failure (0.88, 0.43 to 1.80). Adding depression and sleep disturbance moved the estimates to 0.72 (0.46 to 1.11) and 0.67 (0.33 to 1.38). All of those intervals include 1, which means no significant difference, and they are wide because few melatonin users had heart disease.
The authors do not read this as good news. They write that the estimates "should not be interpreted as evidence that melatonin is cardioprotective, nor do they establish long-term safety". NHANES measures only recent use and a snapshot of disease, so it cannot see years of nightly use. They describe their analysis as hypothesis-generating.
Why two studies can look so different
The comparison below shows why the two results do not contradict each other.
| AHA abstract (TriNetX) | NHANES analysis (Open Heart) | |
|---|---|---|
| Who | Adults with a recorded insomnia diagnosis | General US adult population, 20 and older |
| Melatonin exposure | At least 365 days, from prescription records | Any use in the past 30 days, self-reported |
| Outcome | New heart failure diagnosis within 5 years | Heart failure or other heart disease already present |
| Size | 65,414 users, 65,414 matched controls | 267 users, 50,662 non-users |
| Result | HR 1.89 for incident heart failure | OR 0.88 (0.43 to 1.80) in the core model |
| Review status | Conference abstract, not peer reviewed when presented | Published commentary with a new analysis |
The first study followed people who have insomnia and long melatonin exposure forward in time. The second looked at a snapshot of the general population and recent use. A signal in one and none in the other fits both studies being right about their own population, and it fits confounding in the first. The Open Heart authors call this "methodological heterogeneity rather than a direct contradiction". The AHA authors ask for randomized trials, and the Open Heart authors say better evidence is still to be developed.
What the broader safety reviews cover
The heart failure signal lands on top of a safety literature that was never built for long-term questions. A systematic review of 50 controlled studies of oral melatonin found that 26 reported no statistically significant adverse events and 24 reported at least one. The adverse events were generally minor and short-lived, mostly fatigue, mood or reduced psychomotor and cognitive performance, and a few studies noted effects on blood pressure and heart rate that seemed to depend on dose, timing and interactions with blood pressure drugs.
Foley HM, Steel AE. Adverse events associated with oral administration of melatonin: A critical systematic review of clinical evidence. Complement Ther Med 2019. PMID 30670284
A second review of 37 placebo-controlled trials in people with sleep disorders found daytime sleepiness (1.66%), headache, dizziness and other sleep-related events as the most frequent complaints, with no life-threatening events. Its caveat matters here: participants were followed for up to 29 weeks, most for 4 weeks or less, so the scarcity of long-term trials "limits the conclusions regarding the safety of continuous melatonin therapy over extended periods".
Besag FMC, Vasey MJ, Lao KSJ, Wong ICK. Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review. CNS Drugs 2019. PMID 31722088
The US National Center for Complementary and Integrative Health sums it up on its melatonin page (opened 2 November 2026): short-term use "appears to be safe for most people", and "information on the long-term safety of supplementing with melatonin is lacking" (nccih.nih.gov). The AHA abstract starts from the same gap. For a fuller look at the general question, see Is melatonin safe?. For melatonin as a sleep aid, see Melatonin for sleep. And one contrast worth knowing: a 2025 meta-analysis of four studies in people who already had heart failure reported improved quality of life with melatonin, and no significant change in ejection fraction (mean difference 2.39, 95% CI -1.82 to 6.59). That asks whether it helps an existing condition, a different question from whether it causes one.
Daliri AS, Goudarzi N, Harati A, Kabir K. Melatonin as a Novel Drug to Improve Cardiac Function and Quality of Life in Heart Failure Patients: A Systematic Review and Meta-Analysis. Clin Cardiol 2025. PMID 40026259
What this means if you take melatonin
No study here tells you to stop, and none tells you it is fine to carry on indefinitely. What the evidence supports is smaller. Tell the person who prescribes your other medicines, or your pharmacist, that you take melatonin, how often, and for how long. Over-the-counter supplements are easy to leave out of a medication list, and the Open Heart commentary urges clinicians to record them. If you have heart failure, high blood pressure or take heart medicines, that conversation matters more.
Swelling in the ankles, breathlessness when you lie flat, or breathlessness on stairs that is new for you are reasons to see a doctor now, whatever you take for sleep. They can point to a heart or lung problem that deserves its own check.
The second point is the one both papers share. Melatonin is usually taken because sleep is bad, and the commentary advises prioritizing evaluation and treatment of the underlying sleep disorder. Insomnia has causes with their own fixes, and sleep apnea is one that sound recordings can hint at. Sleep apnea risk factors explains who is most likely to have it.
Where SleepTrace fits
The question behind a worrying headline is usually "what is actually going on in my nights?". SleepTrace listens through the phone's microphone while you sleep and shows what it heard: snoring, talking and coughing come with a short clip you can play back, and possible breathing pauses are marked with a timestamp but no clip. It also gives a sleep apnea indicator as a screening estimate, not a diagnosis, and estimates sleep phases from sound alone. The free plan covers nightly tracking and 3 playable clips a month, on iPhone and Android. The app has to stay open with the screen dimming, and the phone belongs on the charger.
It cannot tell you whether melatonin affects your heart, and it does not see your heart rate unless you also wear an Apple Watch. What it can do is give you something concrete to bring to an appointment: how restless the nights were, whether snoring or pauses show up, and how that changes over weeks.
Frequently asked questions
That has not been shown. In the AHA abstract, adults with insomnia who had used melatonin for a year or more were diagnosed with heart failure more often within 5 years (4.6% against 2.7%) than matched adults who had not used it. The authors call it an association and ask for randomized trials. A 2026 commentary points out that melatonin users in the US survey NHANES reported far more sleep disturbance (57.9% against 20.5%) and depression (13.3% against 5.5%) than non-users, which is the kind of difference that can produce a false signal.
130,828 adults with an insomnia diagnosis in the TriNetX database, split into 65,414 who had used melatonin for at least 365 days and 65,414 matched controls who had not used it. People who already had heart failure or took other prescription sleep drugs were excluded. The data were presented as an abstract at the AHA Scientific Sessions 2025 and were not peer reviewed at that time.
The study cannot answer that for you. Nothing in it shows that stopping lowers anybody's risk. Whether to continue is a conversation for your doctor or pharmacist, who know your heart history and your other medicines, and it helps to mention melatonin by name because it is sold without a prescription and often does not appear in records.
Short-term use appears safe for most people according to the US National Center for Complementary and Integrative Health, and the same page states that information on long-term safety is lacking. Reviews of controlled trials found mostly mild effects such as sleepiness and headache, but most of those trials ran for weeks, not years. The heart failure abstract is one reason the long-term question is being asked again.
A 2025 meta-analysis of four studies in people with heart failure reported improved quality of life, while the change in ejection fraction was not statistically significant (mean difference 2.39, 95% CI -1.82 to 6.59). That asks a different question from the abstract above, and four studies are not a basis for treatment decisions.
SleepTrace is a wellness app, not a medical device. This article is general information, not medical advice. If your symptoms are frequent, severe or worrying, please talk to a doctor.
A conference abstract is not a reason to stop on your own, and it is not a reason to ignore your heart either. Talk to the doctor who treats you; SleepTrace records sound only and shows your estimated sleep phases, snoring and possible breathing pauses, which gives that visit a description of your actual nights. It does not measure your heart or tell you whether melatonin is right for you.
Hear your own night. SleepTrace turns a night of audio into your sleep phases, the sounds you made, and how it all trends. Works without a wearable, better with one. Your phone on the nightstand is enough to start. Get it for iPhone or Android →