A large study presented by the American Heart Association found that adults with chronic insomnia who took melatonin supplements for a year or longer had a 90% higher risk of developing heart failure over five years compared to non-users. The analysis drew on health records for 130,828 adults (average age 55.7) from the TriNetX Global Research Network, matching 65,414 long-term melatonin users against an equal number of non-users across 40 demographic and health factors.
Heart failure occurred in 4.6% of melatonin users versus 2.7% of the control group. Melatonin users were also 3.5 times more likely to be hospitalized for heart failure (19.0% vs. 6.6%) and nearly twice as likely to die from any cause over the five-year period (7.8% vs. 4.3%). A sensitivity analysis limited to people with at least two melatonin prescriptions 90 or more days apart still showed an 82% higher heart failure risk.
"Melatonin supplements may not be as harmless as commonly assumed," said lead author Dr. Ekenedilichukwu Nnadi. "If our study is confirmed, this could affect how doctors counsel patients about sleep aids." The findings are observational and don't prove melatonin causes heart problems, but researchers say they raise questions about the safety of long-term use of one of the world's most popular sleep supplements.