FEV(1) is endorsed by the National Asthma Education and Prevention Program as a means for grading asthma severity. However, few data exist on the relationship between FEV(1) and asthma outcomes during long-term follow-up. We explored the relationship between the percent predicted FEV(1) (FEV(1)%) and subsequent asthma attacks in a longitudinal study of pediatric lung health. A retrospective cohort of 13,842 children (100,292 observations) seen annually over a 15-year interval was analyzed for measurement of pulmonary function, and a respiratory questionnaire was completed. Up to grade 9, a standard questionnaire was completed by a parent or guardian; thereafter it was completed by the patient. For each observation, the report of an attack during the past year was paired with FEV(1) recorded at the field survey 1 year earlier. A progressive decrease in the proportion of individuals reporting an attack was associated with increasing decile of FEV(1)%. Two categorization schemes for FEV(1)% were examined: a scheme based on the National Asthma Education and Prevention Program recommendations (<60%, 60%-80%, and >80%), and an alternative scheme (<80%, 80%-100%, and >100%). In multivariate models, FEV(1)% was an independent predictor of attacks: among the parental report group, the odds ratios were 2.1 (95% CI, 1.3-3.4) and 1.4 (95% CI, 1.2-1.6) for FEV(1)% < 60% and FEV(1)% of 60% to 80% compared with FEV(1)% > 80%, respectively; and among the self-report group, odds ratios were 5.3 (95% CI, 2.2-12.9) and 1.4 (95% CI, 1.2-1.7) for FEV(1)% < 60% and FEV(1)% of 60% to 80% compared with FEV(1)% > 80%, respectively. With the alternative classification scheme, the relationship was similar, but the difference in risk between categories of FEV(1)% decreased. The strong association between FEV(1)% and risk of asthma attack over the subsequent year supports an emphasis on objective measures of lung function in assessment of risk for adverse asthma outcomes.
