People who suffer from sleep apnoea face an increased risk of developing pneumonia, a large epidemiological study indicates.
The association was independent of other known risk factors for pneumonia and might be explained by aspiration of secretions or by impaired immunity in people with apnoea, the authors suggest.
Kun-Ta Chou (Taipei Veterans General Hospital, Taiwan) and co-workers used a national health insurance database to identify 6816 adults with sleep apnoea and 27,284 controls without sleep apnoea between 2000 and 2010.
None of the participants had a history of respiratory infection. During an average 4.5 years of follow-up there were 638 (9.36%) incident pneumonia infections in the sleep apnoea group and 2119 (7.77%) infections in the control group.
This translated into incidence rates of 20.90 and 17.22 per 1000 person–years, respectively, which was a statistically significant difference.
Patients with and without sleep apnoea differed in several respects, particularly in prevalence of comorbidities and medication use. After adjusting for potential confounders, sleep apnoea was a significant, independent risk factor for incident pneumonia, with an adjusted hazard ratio of 1.19.
Subgroup analysis suggested that there was an exposure–response relationship, such that the risk of pneumonia rose in line with the severity of sleep apnoea. The adjusted hazard ratio was 1.32 for people with sleep apnoea who needed continuous positive airway pressure (CPAP) and 1.15 for apnoea patients who did not require CPAP.
Writing in the Canadian Medical Association Journal, Chou and colleagues say that possible explanations include a higher likelihood of pathogen-containing pharyngeal secretions, saliva or oral contents being aspirated into the lower respiratory tract.
“[S]leep apnoea may involve hypercapnia, which has been linked to impaired lung neutrophil function, which could render patients susceptible to pneumonia,” they add.
The researchers conclude: “Sleep apnoea may be a risk factor for pneumonia, and the risk probably increases in accordance with sleep apnoea severity.”
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