Background: FEV1 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 FEV1 and asthma outcomes during long-term follow-up. Objective: We explored the relationship between the percent predicted FEV1 (FEV1%) and subsequent asthma attacks in a longitudinal study of pediatric lung health. Methods: 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 FEV1 recorded at the field survey 1 year earlier. Results: A progressive decrease in the proportion of individuals reporting an attack was associated with increasing decile of FEV1%. Two categorization schemes for FEV1% 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, FEV1% 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 FEV1% < 60% and FEV1% of 60% to 80% compared with FEV1% > 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 FEV1% < 60% and FEV1% of 60% to 80% compared with FEV1% > 80%, respectively. With the alternative classification scheme, the relationship was similar, but the difference in risk between categories of FEV1% decreased. Conclusion: The strong association between FEV1% 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.
- Percent predicted FEV