Purpose: it is well known that people with chronic obstructive pulmonary disease experience declines in functional performance, but little is known about the rate of decline. The purposes of this research were to describe the rate of decline in functional performance and to examine the contribution of disease severity, body composition, symptoms, and functional capacity. Functional performance was defined as the activities that people choose to engage in on a day-to-day basis.
Methods: people (n = 108) with chronic obstructive pulmonary disease were enrolled and followed yearly for 3 yr with self-reported functional performance (Functional Performance Inventory), spirometry, lung volumes, diffusion capacity, body composition (dual-energy x-ray absorptiometry), dyspnea and fatigue (Chronic Respiratory Disease Questionnaire), and functional capacity (6-min walk distance (6MWD), isokinetic strength of knee flexors and extensors, handgrip strength, and maximal inspiratory pressure). A total of 88 subjects completed a (mean ± SD) of 2.7 ± 0.9 yr of follow-up.
Results: significant negative slopes were observed for functional performance (P = 0.001), spirometry (the ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC), P < 0.0001), diffusion capacity (P < 0.0001), and muscle strength (P < 0.0001)). The slopes for dyspnea, fatigue, and functional capacity were not significantly different from zero, but there was a wide individual variation. Hierarchical regression demonstrated that 31% of the variance in the slope of functional performance was accounted for by the hierarchical model, and the primary predictors were the slopes of the FEV1/FVC, 6MWD, and muscle strength (knee flexors/extensor and handgrip).
Conclusions: subjects experienced a slow decline in functional performance, associated with declines in functional capacity and increases in body fat. Symptoms were relatively stable and not associated with declines in functional performance.