Sleeping an extra hour may do your heart good, according to a new study. Every extra hour of sleep observed by researchers was associated with a 33% drop in participants' odds of developing coronary artery calcification over five years.
In the long run that might cut their risk of heart attack or other heart "events," though longer studies are needed to check on that, the researchers note in the Journal of the American Medical Association.
The study tracked new cases of coronary artery calcification among nearly 500 middle-age U.S. adults over a five-year period. The coronary arteries supply oxygen-rich blood to heart muscles. In coronary artery disease, plaque builds up inside coronary arteries' walls, narrowing the arteries. Calcium is one of the components of this plaque. The more plaque that is present, the more calcium is present in the walls of heart arteries. So measuring coronary calcium can be used as a surrogate for measuring plaque.
At the beginning of the study, participants got their coronary arteries scanned using computed tomography at the beginning and end of the study.
Participants also wore devices on their wrists for six days at the study's start to measure their activity, and they provided information on their sleep habits.
The group averaged about six hours of nightly sleep. Few people slept for more than eight hours per night, report the University of Chicago's Christopher Ryan King, and colleagues.
Participants got another coronary artery CT scan at the end of the five-year study. About 12% had developed coronary artery calcification.
People who slept longer -- as confirmed by their wrist monitors -- were less likely to have developed coronary artery calcification.
"One hour more of sleep decreased the estimated odds of calcification by 33%," King's team writes.
Those findings take into consideration participants' age, sex, race, education level, smoking, and sleep apnea risk.
King and colleagues call for further studies to confirm the results, to learn how sleep duration is linked to coronary artery calcification, and to figure out exactly how much sleep is best for reducing coronary artery calcification risk.
[This report reprinted with permission of WebMd Medical News | December 29, 2008 | By Miranda Hitti | Reviewed by Louise Chang, MD]