JAMA: Longer sleep duration linked with less of calcification in coronary arteries
Study participants who slept on average an hour longer per night than other participants had an associated lower incidence of coronary artery calcification, according to research published in the Dec. 24/31 issue of Journal of the American Medical Association.

Recent data suggest that sleep quantity and quality are connected to several 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 wrote.

Christopher Ryan King, BS, of the University of Chicago, 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 CARDIA (Coronary Artery Risk Development In young Adults) study, who were black and white men and women age 35-47 years. At the start of the study in 2000-2001, the researchers said that participants had no evidence of detectable coronary calcification on CT scans.

Potential confounders and mediators were measured at both the start of the study and at five-year follow-up. The investigators examined sleep metrics (wrist actigraphy measured sleep duration and sleep fragmentation, daytime sleepiness, overall sleep quality, self-reported sleep duration) for association with new calcification, based on CT performed in 2005-2006.
King and colleagues found that the incidence of calcification at five years was 12.3 percent. After adjusting for age, sex, race, education, smoking and apnea risk, they found that one hour more of sleep per night decreased the estimated odds of calcification by 33 percent.

The magnitude of the observed association was similar to sizable differences in established coronary risk factors (e.g., one additional hour of sleep reduced risk similarly to a reduction of 16.5 mm Hg in systolic blood pressure), according to the authors. The researchers said that no potential mediators appreciably altered the magnitude or significance of sleep. Alternative sleep metrics were not significantly associated with calcification.

“This study further demonstrates the utility of a simple objective measure of sleep that can be used at home,” the authors wrote. “Future studies will be needed for crucial extensions to these results. First, these results need confirmation in other cohorts. Second, does sleep moderate the rate at which calcification accumulates? Third, will objective sleep tie to coronary disease event outcomes over the long term? While calcification predicts such outcomes, it is difficult to know how and if the predictors of calcification themselves will determine outcomes, or if their impact will be purely mediated by their effect on calcification. Finally, if this association is born out, interventional studies will be needed to guide clinical advice.”