Objective: To estimate the incidence of work disability among adults with asthma and to evaluate a clinically based illness severity score as a predictor of such disability.
Design: Baseline and follow-up telephone interviews and medical record review.
Setting: University-based outpatient pulmonary specialty practice.
Patients: Fifty-six patients interviewed at baseline; 42 reinterviewed 2 years later.
Measurements: Work disability ascertained by interview report and defined as change in job duties, reduction in pay, or change in job or employment status attributed to asthma. Severity of asthma score derived from medical records and based on respiratory symptom frequency, asthma history, and prescribed medications. Pulmonary function by routine testing. Logistic regression analysis of the 5-year incidence of work disability on severity score and forced expiratory volume in 1 s (FEV1).
Results: The 5-year work disability cumulative incidence was 19 percent for change in duties, 17 percent for reduction in pay, 20 percent for change in job or work status, and 36 percent for any of these measures. The median asthma score was 10 (range, 2 to 26). The mean FEV1 as a percent predicted (FEV1 percent) was 88 +/- 25 percent. Score and FEV1 percent were statistically correlated (r = -0.6, p < 0.0001). Severity of asthma score statistically predicted each measure of work disability (p < 0.01). Addition of FEV1 percent added little additional explanatory power to the logistic regression model (maximum chi 2 = 1.3, p > 0.2).
Conclusions: Work disability is common among adults with asthma. A severity of asthma score based on clinical variables is statistically correlated with lung function but appears to be a stronger predictor of disability than airflow measured at one point in time.