For normal nighttime sleepers, taking a midday snooze for more than one hour may hurt cardiovascular health, reports a surprising new study from Guangzhou Medical University, in China. After analyzing 20 studies of 313,651 people, researchers found those people that napped longer than 60 minutes after sleeping more than six hours at night had a 30 percent greater risk of death from any cause and a 34 percent higher risk of heart disease. However, for people sleeping less than six hours at night, naps of 30 to 45 minutes “might improve heart health,” says study author Zhe Pan. Napping, long thought to be healthy, is under increasing scrutiny, with some research linking it to high blood pressure, diabetes and poor overall physical health. A 2019 Swiss study, published in Heart, of 3,500 people concluded that napping once or twice a week reduces heart disease risk by 48 percent, but benefits decline with more frequent naps, perhaps because ongoing sleepiness can point to underlying health disorders.