Among the participants in the study, those who slept an average of one hour longer each night had a lower incidence of coronary artery calcification than those who slept an average of one hour shorter, according to a study in the Dec. 24/31 issue of the Journal of the American Medical Association (JAMA). And coronary artery calcification is a predictive pointer to the development of future heart disease. Risk factors for coronary calcification (i.e., aggregation of calcified plaque seen on computed tomography) include established risk factors for heart disease, such as being male, older age, poor glucose tolerance, tobacco use, dyslipidemia (lipoprotein metabolic disorders, which include hypercholesterolemia), hypertension, obesity, increased inflammatory markers, and low levels of education. Recent data suggest that the quantity and quality of sleep is associated with several of these risk factors. Christopher Ryan King and colleagues at the University of Chicago conducted a test to see if guest-observed sleep duration could predict the occurrence of coronary artery calcification over a 5-year follow-up period. The study included 495 participants from the Coronary Artery Risk Development in Young Adults (CARDIA) study, who were black and white men and women between the ages of 35 and 47. At the start of the study in 2000-2001, no detectable coronary artery calcification was found in these participants on computed tomography. The researchers used sleep measures (e.g., wrist dynamometer) to detect associations between sleep duration and intermittent sleep, daytime sleepiness, overall sleep quality, self-reported sleep duration and new-onset coronary artery calcification. The study was based on the results of computed tomography scans made during 2005-2006. At year 5, the incidence of coronary artery calcification in these participants was 12.3% (for 61 participants). After correcting for age, gender, ethnicity, education level, smoking status and risk of apnea, the researchers found that an extra hour of sleep per night reduced the estimated incidence of coronary artery calcification by 33 percent. The magnitude of this correlation observed by the researchers was similar to the considerable differences that exist in identified risk factors for coronary heart disease (e.g., the risk reduction from an extra hour of sleep is similar to a 16.5 mmHg reduction in systolic blood pressure). There are no possible mediators that could slightly alter the magnitude of the effect of sleep or its significance. There was no significant association between alternative sleep measures and coronary artery calcification. We found a strong and novel association between guest-observed sleep duration and the incidence of coronary artery calcification at 5 years,” the authors of the article write. This study further demonstrates a simple objective measure of sleep that can be used at home.”