Obstructive sleep apnea -- the sleep disorder characterized by pauses in breathing during sleep -- has been linked with a number of health woes, including obesity, heart disease, depression and even cancer. And now, a new study suggests people with sleep apnea may also face a higher risk of pneumonia.
The study, conducted by researchers from Taipei Veterans General Hospital in Taiwan, included 34,100 people, 6,816 of whom had sleep apnea, and 27,284 who did not have the sleep disorder. The participants were followed over an 11-year period.
At the end of the study, researchers found that people with sleep apnea had a 1.20-fold increased risk of developing pneumonia, compared with people without the sleep disorder. Specifically, 638 out of the 6,816 people with sleep apnea developed pneumonia, while 2,119 out of the 27,284 people without sleep apnea developed pneumonia.
In addition, the researchers found that the more severe the sleep apnea, the higher the risk of pneumonia.
While the study did not examine reasons for why sleep apnea could lead to pneumonia, the researchers noted in the study that one explanation could be "increased aspiration risk and impaired immunity."
"Following episodes of apnea-hypopnea, resultant hypoxemia may stimulate patients to breath against a closed airway, therefore causing the intrathoracic pressure to become more negative. The more-negative intrathoracic pressure induces a higher pressure gradient and a vacuum pressure through the upper airway," they wrote in the study.
Another possible reason, they said, was the notion that sleep apnea patients may have an "impaired swallowing reflex" due to decreased upper airway sensation. This could "facilitate aspiration of pathogen-containing pharyngeal secretions, saliva or oral contents into the lower respiratory tract."
Plus, they noted, sleep apnea leads to frequent arousal for sleep, which could have an impact on the immune system -- and its ability to fend off pneumonia.
The study is published in the Canadian Medical Association Journal.