14 DAY TRIAL // Regularly sleeping more or less than seven hours a day increases the risk of cardiovascular disease, a new study published in the August 1 edition of the journal SLEEP suggests. The research was carried out by principal investigator Anoop Shankar, MD, PhD, Associate Professor in the Department of Community Medicine at West Virginia University School of Medicine in Morgantown, West Virginia and lead author Charumathi Sabanayagam, MD.
Data from 30,397 adults that took part in the 2005 National Health Interview Survey was analyzed. The survey gathered information on socioeconomic and demographic characteristics, health and lifestyle. Participants were also asked how many hours of sleep they get in a 24-hour period. 2,146 cases of cardiovascular disease were reported, including angina, coronary heart disease, stroke or heart attack.
Eight percent of the study population reported sleeping five hours a day or less (naps included) and analysis showed that they had twice as much risk of having cardiovascular disease than people who reported seven hours of daily sleep. Nine percent of the subjects reported sleeping nine hours or more a day, and they also had a high risk of cardiovascular disease. All the results were adjusted for race, sex, age, smoking, drinking alcohol, BMI, physical activity, hypertension, diabetes and depression.
Shankar said: “Our study findings suggest that abnormal sleep duration adversely affects cardiovascular health. Sleep disturbances may be a risk factor for cardiovascular disease even among apparently healthy subjects.”
People sleeping for six or eight hours a day also had a risk of cardiovascular disease, even if less serious. The link between sleeping five hours or less a day and cardiovascular disease was strongest in adults under 60 [years of age] and in women. After excluding from the results subjects suffering from diabetes, depression or hypertension, the higher risk of cardiovascular disease remained for people sleeping five hours or less and nine hours or more per day.
People that sleep five hours or less, usually suffer from sleep deprivation that might cause reduced insulin sensitivity, elevated blood pressure and increased sympathetic activity and lead to hardening of the arteries. People that sleep too much, nine hours or more, can cause an underlying sleep-related breathing disorder or poor sleep quality.
“Our study findings may have important clinical and public health implications, such as screening for changes in sleep duration by primary care physicians as a potential risk factor for cardiovascular disease, or initiating public health initiatives focusing on improving sleep quality and quantity,” Shankar said.
Normally, sleep needs vary from one individual to another, relates Science Daily; and as the study's authors did not established a causality between cardiovascular disease and sleep duration, they cannot certify the relationship between the two. Still they suggest that inquiring about sleep duration could help preventive medicine, and advise that most adults should sleep between seven and eight hours a day.