Sleep Apnea Could Lower Aerobic Capacity, Study Finds

People with obstructive sleep apnea (OSA) already experience difficulty in getting a good night’s rest, but they may also tend to take in less oxygen during waking activities such as exercise, a new study has found.

Sleep apnea is a condition that causes the upper airway to become blocked by the soft tissue at the back of the throat during sleep. This results in irregular breathing manifested by symptoms such a snoring and gasping.

It’s known that people with sleep apnea are more likely to be overweight or obese, and therefore less fit aerobically and more prone to cardiovascular conditions such as heart disease. Cardiopulmonary exercise testing (CPET) is a commonly used tool for of heart disease, and a group of researchers noted “there is rising interest in using the procedure for cardiovascular risk stratification of patients with OSA.” Yet, not much is known about the relationship between OSA and exercise capacity. With that in mind, a group of researchers sought to look at the effectiveness of using a VO2max measurement to identify sleep apnea patients at increased risk for heart attack and stroke. This testing could be used to identify earlier, and therefore treat earlier, cases of sleep apnea among those most at risk of severe health complications.

That’s something the researchers sought to change by devising a test comparing the peak oxygen uptake (VO2max) between people with moderate to severe sleep apnea and those with mild – or no – sleep apnea.

To test their hypothesis that OSA is associated with impaired exercise capacity, the researchers followed 15 adults with moderate to severe obstructive sleep apnea and a comparison group of 19 adults with mild or no apnea. Participants pedaled a stationary bike at progressively greater resistance levels and were asked to continue to exhaustion.

The results showed that people with more severe cases of sleep apnea had poorer aerobic fitness as shown by VO2max than those in the comparison group, even if they were the same body size. The researchers found that, on average, those in the sleep apnea group scored 14 percent lower on a VO2 max measurement. Researchers were able to determine upon further analysis that the severity of sleep apnea alone accounted for just over 16 percent of this variability.

Although the study found an association between lower oxygen intake during exercise and sleep apnea, the researchers pointed out that it wasn’t designed show that sleep apnea was the definitive cause of the difference. The researchers said they believe that sleep apnea causes structural changes in muscle, thereby contributing to a more in efficient peak oxygen uptake, and they called for further study to evaluate the effectiveness of CPET for prognostic assessment of patients with OSA.

Reference:

1. Beitler, J. R., et al. "Obstructive Sleep Apnea Is Associated with Impaired Exercise Capacity: A Cross-Sectional Study." Journal of clinical sleep medicine: JCSM: official publication of the American Academy of Sleep Medicine (2014).

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