Extremely hot and cold temperatures both increased the risk of death among people with cardiovascular diseases, such as ischemic heart disease (heart problems caused by narrowed heart arteries), stroke, heart failure and arrhythmia, according to new research published in the American Heart Association’s flagship journal ‘Circulation’. While the researchers don’t know the reason, this may be explained by the progressive nature of heart failure as a disease, rendering patients susceptible to temperature effects. Researchers suggest targeted warning systems and advice for vulnerable people may be needed to prevent cardiovascular deaths during temperature extremes.