According to a study from Vanderbilt University Medical Center, irregular sleep — chronically interrupted sleep and highly fluctuating sleep duration night after night — may increase the risk of atherosclerosis. The study, published in the Journal of the American Heart Association on Feb. 15, looked at 2,032 elderly, socially and ethnically diverse participants from six communities across the United States.

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When participants with more irregular sleep duration were observed for seven days, they were more likely to have higher levels of coronary artery calcium, more plaque in their carotid arteries, and more systemic atherosclerosis and stiffness in their blood vessels, commonly referred to as “arteriosclerosis.”

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“These findings suggest that sticking to regular sleep times or sleeping in the same length of night may play an important role in preventing cardiovascular disease,” said the assistant professor of medicine in the Department of Epidemiology at the Vanderbilt Faculty.

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Shift workers, who are likely to have irregular sleep patterns, and people with existing heart conditions and obstructive sleep apnea, a known risk factor for coronary heart disease, were excluded from the study.

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Disrupting the body's circadian rhythm could be the link between disturbed sleep and cardiovascular disease.

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“Almost all major cardiovascular functions, including heart rate, blood pressure, vascular tone, and endothelial functions, are regulated by circadian clock genes,” the researchers report.

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“A disturbance or maladjustment of circadian rhythms,” they write, “can interrupt these important cardiovascular functions, leading to the promotion of chronic inflammation, changes in glucose metabolism, increased activation of the sympathetic nervous system, and an increase in arterial pressure, all of which promotes the risk of atherosclerosis progression.”

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Among study participants, those with irregular sleep duration had a higher risk of atherosclerosis in the coronary and peripheral arteries. These findings suggest that doctors who encourage their patients to sleep regularly may help reduce their risk of cardiovascular disease, Full said.