Is Long-Term Melatonin Use Putting Your Heart at Risk? Insights, Limitations & Practical Takeaways

R.E. Hengsterman
4 days ago
3 min read

What the recent research found

A recent large-scale analysis presented at the American Heart Association (AHA) Scientific Sessions 2025 examined health-record data for more than 130,000 adults with chronic insomnia to assess long-term use (≥ 12 months) of melatonin supplements. The key findings were:

Among those with documented melatonin for 12 months or more, the incidence of new-onset heart failure over five years was ~4.6 % vs ~2.7 % in matched non-users — a ~90 % relative increase.
Hospitalisation for heart failure was ~19.0 % in the “melatonin” group vs ~6.6 % in the non-user group (~3.5× higher).
All-cause mortality over the follow-up: ~7.8 % for melatonin users vs ~4.3 % for non-users (~2× higher).

The authors emphasise that the findings raise safety concerns given the widespread OTC use of melatonin, and suggest that the assumption of “harmlessness” for long-term use may need revisiting.

Why this is important for nurses and healthcare leaders

As a registered nurse, medical writer and educator crafting content around evidence-based practice and leadership, here are key implications:

Many patients assume “natural” = “safe”. This study challenges that assumption for a common sleep aid in a population with insomnia.
Sleep disturbances and insomnia are themselves major cardiovascular risk factors; distinguishing the effect of the supplement from the underlying sleep disorder is critical.
From a leadership perspective: clinicians, educators and policy-makers should be alert to emerging evidence around supplement use, patient education and long-term safety monitoring.

Interpreting the study: key limitations & caution flags

Observational design — correlation ≠ causation (long-term melatonin use heart risk)

This study is observational, based on electronic health-record data from the TriNetX Global Research Network.
Because of its design, it can only demonstrate an association between long-term melatonin use heart risk and cardiovascular outcomes — it cannot prove that melatonin caused heart failure or death.

Possible confounding & misclassification

The “non-melatonin” group may include many patients in the U.S. who used over-the-counter melatonin that wasn’t recorded in medical records (thus misclassified as non-users).
Severity of insomnia, presence of other sleep disorders (e.g., sleep apnea), psychiatric comorbidity (e.g., depression/anxiety), and use of other sleep aids were not fully accounted for. These may confound the relationship.
Dose, formulation, brand/purity (especially given OTC supplement variability) and actual usage adherence were unknown. Under-documentation is likely.
The study population comprised adults already diagnosed with chronic insomnia — findings may not generalise to people using melatonin short-term, for jet-lag, or without diagnosed insomnia.

Peer-review status & preliminary nature

The work is presented as a conference abstract, not yet a full, peer-reviewed manuscript. This means conclusions are preliminary and should be interpreted with caution.
Because of this stage, other relevant variables or analyses may appear in future full publication that could modify interpretation.

Balanced perspective: what we can and cannot say

We can say

Among a large sample of adults with insomnia, long-term documented melatonin use correlated with higher incidence of heart failure, hospitalisations and death vs non-users.
This raises the question of whether extended use of melatonin merits more caution, especially in populations with cardiovascular risk.
In clinical practice or patient education, it supports the message: use supplements thoughtfully, monitor for long-term safety, and treat root causes of insomnia rather than assuming benign chronic use.

We cannot say

That melatonin causes heart failure, hospitalisation or death.
That the same risk applies to short-term or intermittent melatonin use in otherwise healthy individuals.
That every brand or formulation of melatonin has the same risk profile (given supplement heterogeneity).
That insomnia itself is not contributing to the observed increased risk (it very likely is).

Actionable take-aways for nursing professionals

Educate patients and learners: Emphasise that “natural” doesn’t equal risk-free; the assumption of benign long-term use needs re-evaluation.
Screen for underlying issues: Especially for patients using melatonin long-term, assess severity of insomnia, look for obstructive sleep apnea, depression/anxiety, and cardiovascular risk factors.
Promote sleep hygiene and non-pharmacologic interventions: Cognitive behavioural therapy for insomnia (CBT-I), stimulus control, sleep environment optimisation, circadian hygiene—these remain first-line.
Use supplements judiciously: Guide patients toward short-term use under supervision and review long-term necessity.
Stay current: As an educator and writer, track the full peer-reviewed publication when available, note changes or confirmations of findings, and integrate into leadership or informatics curricula.
Frame content with nuance: Acknowledge both the signal of concern and the limitations of the evidence.

Final thoughts

While this study does not prove that long-term melatonin use causes heart failure, it sends a clear signal: we cannot assume extended use of an OTC “natural” sleep aid is always safe, especially in populations with insomnia and cardiovascular risk.

Author: R.E. Hengsterman, MSN, MA, M.E., RN

Registered nurse, night-shift administrator, and author of The Shift Worker’s Paradox

Nursewhowrites.com

For educational purposes only. Not medical advice.