Washington (IANS): Participants who slept an hour longer than others had a lower incidence of coronary artery calcification, linked with future heart disease.

Risk factors for coronary artery calcification (calcified plaques visible by computed tomography) include established heart disease risk factors like male sex, older age, glucose intolerance, tobacco use, high cholesterol levels and BP, obesity, raised inflammatory markers and the like.

Recent data suggest that sleep quantity and quality are connected to several of these risk factors. "However, some of these correlations have only been documented in studies in which sleep is measured by self-report, which may be biased or insufficiently accurate," the authors write.

Christopher Ryan King, of the University of Chicago (UC) and colleagues tested whether objectively measured sleep duration predicted the development of calcification over five-years of follow-up.

The study included 495 participants from the Coronary Artery Risk Development in Young Adults (CARDIA) study, who were black and white men and women age 35-47 years.

At the start of the study in 2000-2001, the participants had no evidence of detectable coronary calcification on computed tomography scans.

The incidence of calcification at five years was 12.3 percent. After adjusting for age, sex, race, education, smoking and apnea risk, the researchers found that one hour more of sleep per night decreased the estimated odds of calcification by 33 percent.

"We have found a robust and novel association between objectively measured sleep duration and 5-year incidence of coronary artery calcification," the authors write.

"This study further demonstrates the utility of a simple objective measure of sleep that can be used at home. Future studies will be needed for crucial extensions to these results, said an UC release.

These findings were published Wednesday in the Journal of American Medical Association.