Determinants of gait speed in COPD.

BACKGROUND: Measures of physical function, daily physical activity, and exercise capacity have been proposed for the care of patients with COPD but are not used routinely in daily office care. Gait speed is a powerful and simple measure of physical function in elderly patients and seems to be a promising measure for the daily care of patients with COPD. The objective of this study was to comprehensively evaluate the determinants and factors influencing gait speed in COPD, particularly the association of gait speed with objectively measured physical activity and the most used exercise capacity field test in cardiopulmonary disease: the 6-min walk test (6MWT). METHODS: One hundred thirty patients with stable COPD performed two different 4-m gait speed protocols (usual and maximal pace). We modeled gait speed using demographics, lung function, dyspnea, quality of life, physical activity monitoring, exercise capacity, mood, cognitive function, and health-care use. RESULTS: Gait speed was independently associated with 6MWT but not with daily physical activity. The correlation between gait speed and 6MWT was high regardless of protocol used (r = 0.77-0.80). Both 6MWT and gait speed shared similar constructs. Gait speed had an excellent ability to predict poor (≤ 350 m) or very poor (≤ 200 m) 6MWT distances (areas under the curve, 0.87 and 0.98, respectively). Gait speed was not independently associated with quality of life, mood, or cognitive function. CONCLUSIONS: Gait speed is more indicative of exercise capacity (6MWT) than daily physical activity in COPD. Despite its simplicity, gait speed has outstanding screening properties for detecting poor and very poor 6MWT performance, making it a useful and informative tool for the clinical care of patients with COPD.