Tuesday, May 08, 2012

New model gives a better way to study sleep apnea

Obstructive sleep apnea does more than just disrupt a good night’s sleep; it is also linked to an increased risk of stroke. But exactly how this disorder affects the cerebral, or brain, vessels is not known. Researchers at Baylor College of Medicine have created a rat model that mimics this disorder, revealing that after just 30 days of obstructive sleep apnea, cerebral vessels function is altered.

The findings were recently presented at the scientific meeting Experimental Biology 2012 in San Diego.

Model mimics disorder

Obstructive sleep apnea is a disorder in which there are recurring episodes of upper airway collapse during sleep that limits oxygen levels and disrupts sleep. It is estimated to affect 1 in 5 adults in America.

Researchers Randy F. Crossland, graduate student in molecular physiology and biophysics at BCM, David J. Durgan, Eric E. Lloyd, Sharon C. Phillips, associate professor Sean P. Marrelli, and professor Robert M. Bryan, all with the department of anesthesiology at BCM, created the model to mimic the disorder. Most models simply limit oxygen levels, while this model actually induces the closure of the airway.

Using their model, the researchers induced 30 apneas (10-second duration) per hour for eight hours during the sleep cycle for up to one month. After one month of apnea, cerebral vessel dilatory function was reduced by up to 22 percent.

Two important findings

"There are two important findings in these results," said Crossland. "The first is the model itself. The new model allows us to study the complete disease and better understand how repetitive exposure to apnea affects the body. The second is that only one month of moderate obstructive sleep apnea produces altered cerebrovascular function, which could result in a stroke. This finding highlights the detrimental impact the disorder can have on the body."

These results correlate with studies that show similar cell dysfunction in arteries and an increased risk of stroke in people. Damage to the vascular wall in brain arteries could be a factor predisposing an individual with obstructive sleep apnea to stroke.

Rates expected to rise

It is believed that up to 85 percent of patients with clinically significant sleep apnea have not been diagnosed. Obesity and aging are strongly associated with the sleep disorder.

"As the prevalence of obesity is rising and the population continues aging, we expect the rates to rise. It should also be noted that non-obese individuals and even children can have obstructed sleep apnea," Crossland said.

Signs, symptoms

The common signs and symptoms include habitual snoring, daytime sleepiness, enlarged neck size, morning headache, sexual dysfunction and mood and behavioral changes.
The study is supported by the American Physiological Society , which was also one of six scientific societies sponsoring the Experimental Biology 2012 conference

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