Exploring how peak leg power and usual gait speed are linked to late-life disability: Data from the National Health and Nutrition Examination Survey (NHANES), 1999-2002

OBJECTIVE: To investigate the relation of both peak leg power and usual gait speed in their association with varying domains of late-life disability. DESIGN: Participants (?60 yrs of age, n = 1753) were from the National Health and Nutrition Examination Survey, 1999-2002. Disability in activities of daily living, instrumental activities of daily living, leisure and social activities, lower limb mobility, and general physical activities was obtained by self-report. Peak muscle power was the product of isokinetic peak leg torque and peak force velocity. Functional limitations were evaluated via usual gait speed, which was obtained from a 20-foot timed walk. RESULTS: Low usual gait speed was associated with disability independent of basic demographics, cognitive performance, co-morbidities, health behaviors, and inflammatory markers. The odds ratios for disabilities in activities of daily living, instrumental activities of daily living, leisure and social activities, lower limb mobility, and general physical activities for each standard-deviation increase in walking speed were 0.72 (95% confidence interval [CI], 0.59-0.87), 0.63 (95% CI, 0.52-0.77), 0.57 (95% CI, 0.45-0.72), 0.56 (95% CI, 0.47-0.67), and 0.74 (95% CI, 0.64-0.85), respectively. The odds ratios for disabilities in activities of daily living, instrumental activities of daily living, leisure and social activities, lower limb mobility, and general physical activities for each standard-deviation increase in leg power were 0.70 (95% CI, 0.55-0.89), 0.67 (95% CI, 0.53-0.86), 0.62 (95% CI, 0.47-0.83), 0.58 (95% CI, 0.47-0.72), and 0.73 (95% CI, 0.61-0.87), respectively. Supplementary adjustment for walking speed mildly attenuated the relation of leg power to disability. CONCLUSION: Peak leg power and habitual gait speed were associated with varying domains of late-life disability. The association between peak leg power and disability seems to be partially mediated through usual gait speed. Copyright ? 2006 by Lippincott Williams & Wilkins.