Difficult-to-control asthma and ohstructive sleep apnea

This study tested the hypothesis that asthma can promote obstructive sleep apnea (OSA) by looking at the prevalence of OSA among patients with difficult-to-control asthma receiving long-term oral corticosteroid (CS) therapy and examined some possible etiological factors. The study design was a prospective cohort study and was conducted in the pulmonary outpatient clinic of a tertiary care center in Haifa, Israel. Twenty-two consecutive patients with severe unstable asthma, 14 on continuous and 8 on bursts of oral CS, in addition to their standard therapy for a mean of 8.9 +/- 3.3 years, underwent a night polysomnography in a sleep laboratory regardless of sleep complaints. A standard questionnaire was completed upon attending the sleep laboratory. The OSA was defined as respiratory disturbance index (RDI) of greater than or equal to5 and typical complaints. The correlation between RDI to asthma and morphometric parameters was tested. All but one patient had OSA [95.5% prevalence], with mean RDI of 17.7 +/- 2.5. The RDI values were significantly higher in the continuous CS therapy subgroup (21.4 +/- 3.4 vs. 11.1 +/- 1.6, p < 0.05]. The study group had above normal neck circumferences and body mass index. The former increased by 12.1% +/- 3.1% to 29.8% +/- 1% during the oral CS therapy interval but had no significant effect on RDI as a covariant. This study showed an unexpectedly high prevalence of OSA among patients with unstable asthma receiving long-term chronic or frequent burst of oral CS therapy. It may be assumed that prolonged and especially continuous oral CS therapy in asthma increases airway collapsibility.