You’re likely referring to results of a study from South Korea. It concluded that young and middle aged adults who sleep too much or too little, or whose sleep is of poor quality, are at higher risk of heart disease than people in the same age range who slept seven hours a night and reported sleeping well.
The study included more than 47,000 individuals who completed a questionnaire about their sleeping habits and then had tests to assess their heart health. The researchers were looking for early coronary lesions indicated by the presence of calcium deposits on coronary artery walls as well as arterial stiffness. This was evaluated by measuring the velocity or speed of the pulse wave between the arteries in the upper arm and ankle.
Study participants who reported sleeping five or fewer hours had 50 percent more calcium in their coronary arteries than those who slept seven hours a night. Results were even worse in those who slept nine or more hours a day – they had 70 percent more coronary arterial calcium as those who reported sleeping seven hours. Individuals who reported poor quality sleep had more than 20 percent more calcium than those who considered the quality of their sleep to be good.
Participants reporting poor sleep quality also had stiffer arteries than those who slept seven hours a day or who had good sleep quality. Lowest levels of vascular disease were seen in participants who slept seven hours a day and described their sleep quality as good.
You should note that the study relied on self-reports of sleeping habits, which may not be as accurate as objective laboratory assessments of how long and how well the individuals slept, but the researchers concluded that the self-reports might underestimate the cardiovascular risk seen in the study.
Study co-author Chan-Won Kim was quoted in news reports as saying that “coronary calcium develops way before heart attack symptoms occur, and a greater amount of calcium in the coronary arteries predicts future development of heart disease.”
Earlier studies have linked heart problems to poor sleep but this is the first one to look for early signs of heart disease and relate them to too much, too little or poor quality sleep.
According to the National Sleep Foundation, not getting enough sleep puts you at higher risk of heart disease regardless of age, weight, smoking and exercise habits. A study from the University of Pennsylvania published in 2013 found that people who slept less than five hours a night are more likely to be obese and to have high blood pressure, high cholesterol, and diabetes.
Andrew Weil, M.D.
Chan-Won Kim and Yoosoo Chang et al, “Sleep Duration, Sleep Quality, and Markers of Subclinical Arterial Disease in Healthy Men and Women.” Arteriosclerosis, Thrombosis and Vascular Biology, doi:10.1161/ATVBAHA.115.306110
Michael A. Grandner et al, “Habitual sleep duration associated with self-reported and objectively determined cardiometabolic risk factors.” Sleepmedicine, DOI: http://dx.doi.org/10.1016/j.sleep.2013.09.012