Not enough sleep can cause atherosclerosis — the hardening and narrowing of arteries — which is the usual cause of heart attacks and strokes.
Ordovas and the other researchers tracked nearly 4,000 Spanish adults whose average age was 46 and had no heart disease when the study began.
People who slept fewer than six hours a night were 27 percent more likely to have bodywide atherosclerosis than those who slept seven to eight hours, Ordovas and his team reported.
But too much sleep was shown to be problematic as well. Women in the study who slept more than eight hours a night also had an increased risk of atherosclerosis.
» Too much sleep linked to early death, disease risk
The study also found that participants with "poor-quality" sleep, meaning they awoke often during the night or had trouble falling asleep, were 34 percent more likely to have atherosclerosis.
"This is the first study to show that objectively measured sleep is independently associated with atherosclerosis throughout the body, not just in the heart," Ordovas said in a news release.
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