Longitudinal limits of normal decline in lung function in an individual

Objectives: The objectives of this study were to propose a method of calculating longitudinal limits Of normal decline (LAD) in forced expiratory volume in I second to identify individuals with an excessive decline in lung function and to compare the method with other published LAD methods. Methods: We used longitudinal data from 11 workplace-based spirometric monitoring programs conducted from 1987 to 2001 on 12,729 workers to evaluate effectiveness of each LAD method in identifying a true excessive decline in forced expiratory volume in I second defined using two criteria: slope > 60 mL/year or > 90 mL/year estimated over 5 or more Years of follow up. Results: In. comparison to the LAD proposed by the American College of Occupational and Environmental Medicine, the proposed method had 5.0 to 2.7 times higher sensitivity over years I through 5 for the > 60-mL/yr criterion. Conclusions: The proposed LAD method was more effective than the other methods for identifying excessive declines.