Functional Performance in Chronic Obstructive Pulmonary Disease Declines with Time

Purpose. It is well known that people with chronic obstructive pulmonary disease (COPD) experience declines in functional erformance, but little is known about the rate of decline. The purpose of this research was 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 COPD were enrolled and followed yearly for three years 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 (six-minute 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 years of follow-up. Results. Significant negative slopes were observed for functional performance (P=0.001), spirometry (the ratio of forced expiratory volume in one second 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 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.