Copyright nytimes
What were its limitations? One of the study’s major drawbacks is that it only counted people with documented melatonin prescriptions. In the United Kingdom and several European Union countries, getting melatonin requires a prescription, but in the United States and some other countries, anyone can buy melatonin supplements over the counter without consulting a doctor. This means that some of the participants in the study’s non-melatonin group may actually have been taking the supplements too, even if it wasn’t reported in their medical records. This muddies the comparison, said Dr. Andrew W. McHill, a sleep and circadian rhythm scientist at Oregon Health & Science University. It also lacked information about melatonin dosage and insomnia severity, said Dr. Phyllis Zee, a sleep doctor and researcher at Northwestern Medicine who was not involved with the study. Both of these factors could affect heart risks. Dr. Kansagra also noted that the risk of heart failure was quite low in both groups. To understand whether melatonin increases heart failure risks, researchers would need to conduct randomized controlled trials assigning people to receive either melatonin supplements or placebos, said Dr. Akinbolaji Akingbola, a sleep medicine physician at the University of Minnesota, who was also not involved in the study. Dr. Nnadi acknowledged the need for further study. One of his goals in conducting the study, he said, was to drum up more research into over-the-counter supplements like melatonin.
