Sleep-disordered breathing and asthma

Asthma and obstructive sleep apnea are highly prevalent and often coexisting diseases. It has been hypothesized that a bidirectional relationship may exist between them, mediated by common risk factors, such as inflammation, obesity, rhinitis and gastroesophageal reflux. However, there is no firm evidence yet confirming a mutual influence between obstructive sleep apnea and asthma, and the relationships between obstructive sleep apnea severity and asthma severity or control of asthma remain unclear. This may be partly due to methodological issues of the available studies, for example the frequent use of questionnaires rather than objectively-based evaluation of both diseases. Many studies suggest that asthmatic patients are at increased risk for obstructive sleep apnea. On the other hand, some symptoms of obstructive sleep apnea such as excessive daytime sleepiness are frequent in asthmatic subjects and are associated with poor sleep quality or insomnia. Continuous positive airway pressure (CPAP) treatment, or adenotonsillectomy in children, appears to improve clinical symptoms or exacerbation frequency in asthmatic subjects, whereas use of continuous positive airway pressure in asthmatic patients without obstructive sleep apnea seems to exert no effect on asthma or bronchial hyperreactivity. Welldesigned and longitudinal studies on large samples are needed to better understand the interrelationships between asthma and obstructive sleep apnea, especially regarding patients with severe asthma.