Interesting and importantly both groups were those who had insomnia and those who had previously been diagnosed with heart failure were excluded.

I don't have access to the actual study but I wonder if they had access to any metrics for the individuals that could quantify the intensity of the insomnia. Chronic insomnia/sleep deprivation is already correlated with heart disease. Could it be that the people with worse insomnia were more likely to take melatonin but also more likely to have heart issues due to the insomnia alone?

> “Worse insomnia, depression/anxiety or the use of other sleep-enhancing medicines might be linked to both melatonin use and heart risk,” Nnadi said. “Also, while the association we found raises safety concerns about the widely used supplement, our study cannot prove a direct cause-and-effect relationship. This means more research is needed to test melatonin’s safety for the heart.”

This seems pretty critical, no? I would assume that melatonin use increases with the severity of insomnia, and persistent lack of sleep has a whole host of long-term health implications. So insomnia a priori seems highly likely to cause both increased melatonin consumption and heart disease. Given how obviously confounded this causal system is, it's practically negligent to not at least control for severity of insomnia or something. Ideally they should have done a matched study or DID or something, but without any attempt to account for the confounding this study is just clickbait.

melatonin is an awsome dream drug great for a midwinter cleanup of the unconsious attic but looses its zap, quickly

"People who are concerned enough about their insomnia to get a prescription from their doctor and take it regularly are more likely than other people to have heart problems and other health issues"

Good to know but maybe not particularly compelling?