Sleep disruptions may increase heart disease risk

By Michelle Rizzo

NEW YORK (Reuters Health) - Relatively healthy individuals who experience sleep disruptions at night appear to have an increased risk activity of factors associated with the development of a blood clot, also referred to as a thrombus.

"There is an extensive literature demonstrating that sleep disruption is associated with increased coronary artery disease risk, but the possible mechanism for that association has been unclear," lead author Dr. Joel E. Dimsdale, of the University of California San Diego, told Reuters Health.

"In previous work, we have found that sleep disruption was associated with pro-coagulant activity in patients with obstructive sleep apnea and in patients facing major life stress," he continued. "The current study reports similar findings even in a relatively healthy population."

Dimsdale and colleagues examined whether sleep disruptions, verified by polysomnography, were associated with increased levels of prothrombotic factors previously shown to predict the risk of coronary artery disease. The findings are published in the medical journal Chest.

A polysomnograph, conducted in a sleep laboratory, involves the measurement of brain waves to record sleep cycles and stages, plus monitoring muscle activity, eye movement, breathing rate, blood pressure, blood oxygen levels and heart rate. The patient is also directly observed during sleep.

A total of 135 unmedicated subjects, an average of 37 years old, without a history of sleep disorders underwent full-night polysomnography. The researchers also recorded blood levels of factors associated with blood clotting and oxygen saturation. In their analyses, they accounted for the effects of age, gender, ethnicity, body mass index, blood pressure, and smoking history.

The investigators found that a higher score on total arousal index and longer periods of wakefulness interrupting sleep were associated with higher levels of the von Willebrand Factor antigen and soluble tissue factor antigen, respectively, both of which are linked with blood coagulation.

An association was also observed between average oxygen saturation levels of less than 90 percent and the plasminogen activator inhibitor antigen, also involved in coagulation, although this relationship was not statistically significant.

"Our findings suggest that sleep disruptions, even in a relatively healthy population, are associated with a prothrombotic state that might contribute to coronary artery disease," the authors conclude.

SOURCE: Chest, March 2007.