Long-term melatonin use linked to about 90% higher heart failure risk

Using the TriNetX Global Research Network, investigators compared adults diagnosed with chronic insomnia who had at least one year of recorded melatonin use to a matched cohort without any melatonin records. Over a five-year follow-up, the melatonin users experienced a roughly 90% increase in heart-failure diagnoses (4.6% versus 2.7%). When the analysis required two prescriptions spaced at least 90 days apart, the risk remained elevated at about 82%.

Hospitalizations for heart failure were nearly 3.5 times higher in the melatonin group, and all-cause death occurred in 7.8% of users compared with 4.3% of non-users. Lead author Ekenedilichukwu Nnadi emphasized that melatonin is often considered safe, yet the findings raise safety questions. Experts noted that over-the-counter availability and lack of dosage data limit the conclusions, and further research is needed to determine any causal link.