Severity Of Obstructive Sleep Apnea Linked To Sedentary Lifestyle

Main Category: Sleep / Sleep Disorders / Insomnia
Article Date: 23 Jan 2009 - 4:00 PDT

email to a friend   printer friendly   opinions  

Not only is Obstructive Sleep Apnea linked to insulin resistance and liver disease independent of obesity, but at least one risk factor is also common to obesity and Obstructive Sleep Apnea: prolonged daytime sitting or standing. Even when the sedentary lifestyle does not lead to obesity, it may still lead to Obstructive Sleep Apnea and its concomitant health risks, according to another research article in the first issue for February of the American Journal of Respiratory and Critical Care Medicine.

"Overnight fluid displacement from legs, related to prolonged sitting, may play a previously unrecognized role in the pathogenesis of Obstructive Sleep Apnea," wrote principle investigator, T. Douglass Bradley, M.D., professor of medicine and director of the Centre for Sleep Medicine and Circadian Biology at the University of Toronto,

The research also found that the volume of fluid shift was directly linked to the hours in a day that the subject reported sitting or standing and was independent of the excess weight that often accompanies sedentary lifestyles.

"In more recent years, the introduction of modern technologies into the workplace has greatly reduced the need for physical activity and increased the number of jobs requiring prolonged sitting, during which absence of the contraction of calf muscles leads to dependent fluid accumulation in the legs that is proportional to the time spent in that position," explained Dr. Bradley. "When assuming the recumbent position at bedtime, the fluid retained in the legs during the day in redistributed to the upper body. It is therefore plausible that some of the displaced fluid might reach the neck and predispose to upper airway constriction."

To determine whether that, in fact, was the case, the researchers recruited 23 nonobese subjects who were being evaluated for suspected Obstructive Sleep Apnea and performed standard sleep studies that assessed each subject for sleep stages and number of arousals, as well as oxygen saturation of the blood. The circumferences of their calves and necks were also measured at bedtime and upon awakening, before they got up.

Indeed, they found that the only significant correlate factor with respect to severity of Obstructive Sleep Apnea was the overnight change of fluid volume in the leg, which explained 67% of the variance in Obstructive Sleep Apnea severity. The change in fluid in the leg was, in turn, directly related to the amount of time the subject reported sitting each day.

"An important implication of our observations is that sedentary living may predispose to Obstructive Sleep Apnea not only by promoting obesity, but also by causing dependent fluid accumulation in the legs, which can shift rostrally to the neck overnight," said Dr. Bradley.

This finding may also help explain why 40 percent of patients with Obstructive Sleep Apnea are not obese, and why a reduction in Obstructive Sleep Apnea has been described when subjects begin exercise programs, even in the absence of weight loss.

This news briefing is based on an article published in the American Thoracic Society's peer-reviewed journal, the American Journal of Respiratory and Critical Care Medicine.

About the ATS

Founded in 1905, the American Thoracic Society is the world's leading medical association dedicated to advancing pulmonary, critical care and sleep medicine. The Society has more than 15,000 members who prevent and fight respiratory disease around the globe, through research, education, patient care and advocacy.

American Thoracic Society

• Additional
• References
• Citations