Impairments in Systems Underlying Control of Balance in COPD

BACKGROUND: Although balance deficits are increasingly recognized in COPD, little is known regarding the disordered subcomponents underlying the control of balance. We aimed to determine the specific components of balance that are impaired in COPD and to investigate the association among balance, peripheral muscle strength, and physical activity. METHODS: Balance, physical activity, and lower extremity muscle strength were assessed in 37 patients with COPD and 20 age-matched healthy control subjects using the Balance Evaluation Systems Test (BESTest), the Physical Activity Scale for the Elderly, and an isokinetic dynamometer, respectively. A subset of subjects (20 patients with COPD and 20 control subjects) underwent a second testing session in which postural perturbations were delivered using a lean-and-release system. RESULTS: Subjects with COPD (age, 71 ± 7 years; FEV(1), 39% ± 16% predicted) exhibited significantly lower scores than did control subjects (age, 67 ± 9 years) on all of the BESTest subscales (all P < .001). In response to anterior perturbations, subjects with COPD showed a longer time to foot-off (P = .027) and foot contact (P = .018), and a longer duration anticipatory phase (P = .008) compared with control subjects. Muscle strength (P = .008) and self-reported physical activity (P = .033) explained 35% of the variance in balance in subjects with COPD. CONCLUSIONS: Individuals with COPD exhibit impairments in all balance subcomponents and demonstrate slower reaction times in response to perturbations. Deficits in balance are associated with reduced physical activity levels and skeletal muscle weakness.