RESEARCHERS SHOW WEAKENED DIAPHRAGM MUSCLES MAY CONTRIBUTE TO SLEEP APNEA IN THE OBESE
CINCINNATI -- Research on the respiratory system being conducted at the University at Buffalo may shed new light on the causes of sleep apnea, brief episodes during the night when breathing ceases, depriving the brain of oxygen.
Results of the research were presented here today (May 30, 1996) at the annual meeting of the American College of Sports Medicine.
Sleep apnea occurs most often among people between the ages of 30 to 40 years who are overweight. It can cause excessive sleepiness during the day, which can disrupt work and social life.
Using rats as an animal model, Gaspar Farkas, Ph.D., UB associate professor of physical therapy and exercise science, and colleagues showed that weakened diaphragm muscles, the muscles most responsible for breathing, may be one of the factors contributing to the condition.
The researchers measured diaphragm function in lean and obese rats over a normal 18-month lifetime, testing them when they were young (6-8 weeks), mature (10-12 months) and old (17-18 months). They found that diaphragm muscles in the obese animals lost their ability to respond forcefully as the animals aged. Diaphragm response in the obese young animals was not compromised.
Farkas said his group's earlier research on abnormalities of the respiratory system showed that obese rats respond in much the same way as morbidly obese humans, making this a good model for studying impaired human respiratory mechanisms.
"The diaphragm is the only respiratory muscle that is active during REM sleep, and in obese people it is already overloaded," Farkas said. "We have shown that these muscles become weakened with age, at a time when load and stress on these muscles are already great, so it's a double deficit.
"This finding helps to explain why an obese person may not have problems with sleep apnea at 20, but may have problems at 50," he added. Farkas and his group will continue their research by looking at different factors and their effects on the respiratory systems in obesity.
Researchers from the University of Florida at Gainesville and the University of South Dakota also participated in the study.