Is sleeping good for the heart?

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Just one extra hour of sleep a day appears to lower the risk of developing calcium deposits in the arteries, a precursor to heart disease, according to ABC News.
A study published this week in the Journal of the American Medical Association by Christopher King and colleagues from the University of Chicago has found a relationship between sleep quantity (hours spent asleep) and calcium build up -- or calcification -- in the arteries that supply the heart muscle with blood.
For each additional hour of sleep, the risk of calcification of the coronary arteries decreased by 33 per cent -- an outcome equal to reducing blood pressure by 16 point elevations.
Moreover, the sleep relationship did not change even when the researchers controlled for certain traditional risk factors for heart disease, such as cholesterol, weight and diabetes.
The results were part of the ongoing Coronary Artery Risk Development in Young Adults Study (CARDIA), which is being carried out at four cities nationally.
This report focused on nearly 500 patients at the Chicago CARDIA site.
Participants were black and white men and women aged 35-47 years, measured initially in 2000-2001 and followed up in 2005-2006.
Sleep was measured by a wrist band recording wrist movement on an initial Wednesday through Saturday night period.
This wrist recorder is a very good measurement of time spent asleep -- nearly as good as sleep measured in a sophisticated sleep laboratory.
However, the wrist band is less disruptive to normal sleep than sleeping in a sleep lab, because there is no "first-night" effect -- the disruption of the normal sleep structure of a subject that is often seen with more intrusive testing.
The amount of calcium in the coronary arteries was measured by CT scanning of the heart.