Common Supplement [melatonin] Shows Concerning Link to Heart Failure

People who are prescribed melatonin have seen a doctor for sleep or other health disturbances.

Heart failure is strongly associated with sleep disturbances, see e.g.: https://www.nature.com/articles/nrcardio.2016.71

So all of this could be putting the cart before the horse. People who see the doctor for sleep issues -- or related health issues -- are more likely to die of heart failure for reasons that have absolutely nothing to do with their melatonin prescription in itself.

You've got to run an analysis in healthy people who take melatonin via unprescribed supplements or from dietary sources. I'd bet it finds no increased morbidity.

I'd also bet that you find increased morbidity in people who take other prescription soporifics.