Inhaled corticosteroids: Impact on asthma morbidity and mortality

Inhaled corticosteroids are now recommended as first-line therapy for asthm a, Although these drugs clearly improve the symptoms of the disease and the associated physiologic abnormalities, epidemiologic studies provide import ant information on their effectiveness in preventing asthma morbidity and m ortality. We review the evidence regarding the role of inhaled corticostero ids in the prevention of asthma fatality and hospitalization. In the proces s, we discuss the methodologic complexities of the nonexperimental studies and the implications of the methodologic issues on the evaluation of the im part of these drugs. Eight of the cohort and ecologic studies conducted to date strongly suggest that inhaled corticosteroids. when taken regularly, d ecrease the number of hospitalizations for asthma by up to 80%. For asthma death, the results of 11 investigations appear less consistent, especially those of several cohort and case-control studies whose principal objective was to examine not the benefit of inhaled corticosteroids but the adverse e ffects of other drug classes, Much of the inconsistency in the results, how ever, can be explained by weaknesses in study design and analysis-in partic ular, the failure to consider exposure in terms of regular use of inhaled c orticosteroids. When the most recent study involving the use of the Saskatc hewan databases is considered, it is evident that regular treatment with co nventional or low-dose inhaled corticosteroids results in a significant red uction in fatalities due to asthma, In all, the evidence to date strongly i ndicates that regular use of inhaled corticosteroids, even at low doses, wo uld prevent the major portion of asthma hospitalizations and deaths.