The prevalence of obstructive sleep apnea (OSA) is high in patients who have asthma, according to a new study, and OSA appears to be an important factor that gives rise to severe exacerbations.
Patients with asthma who have OSA are 14 times as likely to have severe exacerbations as those who do not have OSA, the results show.
Previous studies have shown that the incidence of OSA is higher in patients with asthma, but whether OSA affects severe exacerbations in patients with asthma remained unclear. This cross-sectional study of 146 patients with asthma and 157 matched-controlled patients investigated the prevalence of OSA in asthma and examined prospectively the significance of the effect of OSA on severe asthma exacerbations, stated the researchers, led by Dr Ke Hu of the Division of Respiratory Disease at Renmin Hospital, Wuhan University, in Wuhan, China.
The researchers prospectively studied the patients for 1 year, identifying exacerbation episodes based on the patients’ medical histories. They determined lung function and the percentages of eosinophils in induced sputum samples and evaluated the frequencies of severe asthma exacerbations during the previous year in the group of patients who had asthma.
The patients had full-night polysomnography, and the researchers recorded severe asthma exacerbations among the patients over a 4-year period.
The rates of OSA were 19.2% (28 of 146 patients) among those with asthma and 9.6% (15 of 157 patients) among the controls.
“The frequency of severe asthma exacerbations was significantly higher among the asthma patients with OSA compared with those who did not have OSA,” the researchers stated. The relative risk of OSA in patients with asthma was 2.25. Patients with asthma who had OSA also had more severe exacerbations, with a relative risk of 14.23.
The apnea–hypopnea index (AHI) correlated significantly with the number of severe asthma exacerbations. Logistic regression analyses determined that the AHI was significantly associated with the occurrence of severe asthma exacerbations.
“These are novel findings that highlight the importance of OSA assessments for patients with asthma who present with OSA indicators, such as snoring, obesity, and daytime sleepiness,” the researchers stated.
They suggested that repeated episodes of hypoxia and reoxygenation that occur during OSA may lead to systemic inflammation that affects the airway and aggravates asthma. “It remains unclear whether OSA alters pulmonary function, which is a risk factor for acute exacerbations,” they stated. “Further studies are needed to determine whether the observed increase in acute exacerbations arose as a consequence of differing incidences of OSA in asthma patients or whether OSA reduces lung function in asthma patients.”
The clinical significance of the findings, the researchers stated, is that “inattention to OSA evaluations in these patients may lead to diagnostic and treatment delays and to increases in the frequency of severe acute exacerbations. Thus, we hope that the findings from our study encourage practitioners to consider screening for OSA and to consider the clinical outcomes.”
The researchers published their results online September 29, 2016 in Sleep Medicine.