New research shows taking melatonin for long periods of time could be a sign of underlying heart issues. Data released by the American Heart Association found that long-term use of the popular sleep aid is actually linked to a higher risk of heart failure and early death in adults with insomnia. Now, there is no evidence that the supplements themselves cause this, but experts say the need to take these supplements on a regular basis could mean that something more serious is going on with your. ...