Background: Clinical practice guidelines for asthma care emphasize the use of objective measures of asthma severity, and yet little data exist on the relationship between FEV(1) and asthma outcomes over long-term follow-up.
Methods: We explored the association between measures of FEV(1) percentage of predicted (FEV(1)% predicted) and subsequent asthma attacks over 3-year intervals. Subjects were identified from two longitudinal cohort studies conducted in the United States and the Netherlands. Persons were included in the analysis if they reported ever having an attack of wheezing with associated shortness of breath prior to or during the follow-up period.
Results: Over the course of longitudinal follow-up at 3-year intervals, 195 subjects in the Netherlands cohort contributed 510 observations, and 698 subjects in the US cohort contributed 1,268 observations (for each observation, the report of an attack since their last visit was paired with the subject's FEV(1) recorded 3 years prior). Overall, subjects in the Netherlands cohort experienced 114 attacks (22% of the observations) and subjects in the US cohort had 517 attacks (40.6% of the observations). FEV(1)% predicted was significantly associated with risk of an asthma attack over the 3 years following its measurement. After adjusting for current smoking and gender, FEV1% predicted remained an independent predictor of subsequent asthma attacks.
Conclusions: These findings support the use of spirometry as an objective measure of asthma severity and risk of adverse outcomes.