An extra hour of sleep at night makes most people get up next morning on the right side of the bed. And according to a study published in today’s JAMA, people who habitually get that extra hour or more may have better cardiovascular health.

Longer sleep, according to research led by University of Chicago epidemiologist Dr. Diane Lauderdale, PhD, makes for substantial reduction in the risk of developing hardened, or calcified, arteries. Coronary artery calcification involves the accumulation of calcified plaques in artery walls. The new research has found an unexpected link between this condition and sleep.

“We have found a robust and novel association between objectively measured sleep duration, ” Lauderdale writes, “and 5-year incidence of coronary artery calcification. One hour more of sleep decreased the estimated odds of calcification by 33%.”