Epidemiology of asthma exacerbations.

Exacerbations of asthma sufficient to require urgent medical intervention are often, but not always, associated with viral infection, especially rhinovirus, with significant interaction with allergen sensitization and exposure. Seasonal patterns of exacerbations are seen especially in children, and may be aggravated by lack of adequate maintenance anti-inflammatory drug treatment during the high-risk viral season most well described in the Northern Hemisphere after school return in September. Age and sex differences in the epidemiology of exacerbations remain less than fully explained, but hormonal influences are demonstrable. Frequent exacerbations may be an indication of greater severity of disease, significant comorbidities, or poor compliance with therapy. Recognizing risk factors for exacerbations and implementing appropriate long-term management strategies coupled with improved compliance should reduce morbidity and mortality associated with asthma exacerbations.