BackgroundContinuous positive airway pressure (CPAP) in asthma patients with concomitant obstructive sleep apnea syndrome (OSAS) seems to have a favorable impact on asthma, but data are inconsistent due to methodological limitations of previous studies. MethodsProspective, multicenter study. We examined asthma outcomes after 6 months of CPAP in 99 adult asthma patients (mean age 57 years) with OSAS (respiratory disturbance index 20). Asthma control and quality of life were assessed with the Asthma Control Questionnaire (ACQ) and the Mini Asthma Quality of Life Questionnaire (MiniAQLQ), respectively. Data were analyzed by intention-to-treat basis. ResultsThe mean SD score of the ACQ decreased from 1.39 +/- 0.91 at baseline to 1.0 +/- 0.78 at 6 months (P = 0.003), the percentage of patients with uncontrolled asthma from 41.4% to 17.2% (P = 0.006), and the percentage of patients with asthma attacks in the 6 months before and after treatment from 35.4% to 17.2% (P = 0.015). The score of the mAQLQ increased from 5.12 +/- 1.38 to 5.63 +/- 1.17 (P = 0.009). There were also significant improvements in symptoms of gastroesophageal reflux and rhinitis, bronchial reversibility, and exhaled nitric oxide values (all P < 0.05). No significant changes were observed in drug therapy for asthma or their comorbidities nor in the patients' weight. ConclusionsAsthma control (both actual and future risk), quality of life, and lung function improved after starting continuous positive airway pressure in asthmatics with moderate to severe obstructive sleep apnea syndrome.