Obstructive and restrictive lung disease and functional limitation: data from the Third National Health and Nutrition Examination

Objective. To determine functional limitations in adults with obstructive or restrictive lung disease or respiratory symptoms. Design. Cross-sectional study. Subjects. Adult participants in phase 2 of the Third National Health and Nutrition Examination Survey, 1991-94. Methods. We classified subjects using spirometric criteria into the following mutually exclusive categories using the forced expiratory volume in 1 s (FEV1), the forced vital capacity (FVC), the FEV1/FVC ratio and the presence of respiratory symptoms: severe obstruction, moderate obstruction, mild obstruction, respiratory symptoms only, restrictive lung disease and no lung disease. We developed regression models to predict functional limitations (unable to walk a quarter of a mile, unable to lift 10 pounds, needs help with daily activities) that controlled for age, race, sex, education, smoking status, body mass index and comorbid conditions. Results. Severe and moderate obstruction were associated with an increased risk of being unable to walk a quarter of a mile [odds ratio (OR) 8.4, 95% confidence interval (CI) 3.6, 19.9 and OR 2.4, 95% CI 1.4, 4.0]. Restrictive lung disease and the presence of respiratory symptoms in the absence of lung function impairment were also associated with an increased risk of this outcome (OR 2.8, 95% CI 1.4, 5.6 and OR 2.8, 95% CI 2.0, 3.9). Similar results were obtained for the outcomes of being unable to lift 10 pounds or needing help with daily activities. Conclusions. The presence of obstructive or restrictive lung disease, or respiratory symptoms in the absence of lung function impairment is associated with increased functional impairment.