This study is the first large, prospective evaluation of the effects of early intervention with inhaled corticosteroids on asthma progression, as determined by the development of severe asthma-related events and changes in lung function. In this study, average duration of time since asthma diagnosis was < 1 year. The study demonstrated that treatment with low doses of inhaled budesonide improved both prebronchodilator and postbronchodilator FEV1, and this effect persisted over the 3 years of the study. However, despite the benefits of inhaled budes-onide, the postbronchodilator FEV1 declined in both treatment groups over the duration of the study. This article extends the description of the results previously described by focusing only on the effects of early intervention with inhaled corticosteroids on lung function, the distribution of the response, and the factors that may determine the response. website
Almost all the patient population studied had symptoms more than weekly but less than daily, with a mean baseline prebronchodilator FEV1 value > 85% and postbronchodilator value > 95%, which would characterize this group as having mild persistent asthma according to the revised Global Initiative on Asthma guidelines. However, a proportion of the patients has a prebronchodilator (but not post-bronchodilator) FEV1 <80% of predicted normal. The effects of the intervention with inhaled budes-onide were similar, in all respects, if these patients were considered as a separate group, when compared to the whole population. Despite the fact that asthma was new onset, the mean baseline postbron-chodilator FEV1 was reduced by 3.7%, suggesting that airway structural changes that result in a decline in FEV1 begin early in asthma.
This information is consistent with a longitudinal birth cohort, initially studied at aged 9 years, which has demonstrated that pulmonary function was consistently lower in individuals with persistent wheezing than in those without persistent wheezing and that tracking of lung function occurred, with those with the lowest lung function in adulthood having the lowest values in childhood, suggesting that the changes occur early in the disease process.
Another explanation for the lower baseline FEV1 may be imprecision in calculating the percentage of predicted normal values. For this reason, the baseline values were recalculated using prediction equations produced by Knudson et al and Hankinson et al for white subjects. For other races, the same race correction factors as given above were used. Now the baseline postbronchodilator FEV1 values for the population were 97.5% (SD 13.9%) and 95.5% (SD 14.9%), respectively. Thus, the baseline reduction in postbronchodilator FEV1 is unlikely to be explained by predicted value equation.