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.