Sleep irregularity -- chronically disrupted sleep and highly variable sleep durations night after night -- may increase the risk for atherosclerosis, according to a study led by Kelsie Full, PhD, MPH, of Vanderbilt University Medical Center.

The multicenter study followed 2,032 older, racially and ethnically diverse participants from six communities across the US. When monitored over a seven-day period, participants with greater irregularity in their sleep duration were more likely to have a higher burden of coronary artery calcium, more plaque in their carotid arteries, and greater systemic atherosclerosis and stiffness in their blood vessels - i.e., "hardening of the arteries."

"These results suggest that maintaining regular or habitual sleep durations, or sleeping close to the same total amount of time each night, may play an important role in preventing cardiovascular disease," said Full. Health professionals who encourage their patients to maintain regular sleep patterns can help them reduce their risk of cardiovascular disease.

Disruption of the body’s circadian rhythm may be the link between disrupted sleep and cardiovascular disease, the researchers suggest. "Almost all major cardiovascular functions, including heart rate, blood pressure, vascular tone, and endothelial functions, are regulated by circadian clock genes."

"Disruption or misalignment of circadian rhythms," they wrote, "can interrupt these important cardiovascular functions, resulting in the promotion of chronic inflammation, alterations in glucose metabolism, heightened sympathetic nervous system activation, and increases in arterial pressures, all predisposing to the risk of atherosclerosis progression."

The study excluded shift workers, who are likely to have irregular sleep patterns, and those with existing heart disease and obstructive sleep apnea, a known risk factor for coronary artery disease.

Read the full study, published February 15 in the Journal of the American Heart Association, here