Determinants of physical performance in ambulatory patients on hemodialysis

Background. Physical performance measures, particularly gait speed, have been useful as predictors of loss of independence. institutionalization, and mortality in older nonuremic individuals. Gait speed has not been evaluated as a predictor of these important outcomes in patients on hemodialysis, nor have the determinants of gait speed in the dialysis population been studied. Methods. We performed a cross-sectional analysis to determine whether demographic, clinical, or nutritional status variables were related to physical performance in a group of 46 hemodialysis patients treated at three University of California San Francisco-affiliated dialysis units. Three physical performance measures were examined, including gait speed, time to climb stairs. and time to rise from a chair five times in succession. Forward stepwise linear-regression analysis was performed with each physical performance measure as the dependent variable and the following candidate predictor variables: age, gender, body mass index. dialysis vintage, Kt/V, albumin. blood urea nitrogen, creatinine, hematocrit, lean body mass, phase angle, ferritin, and the following comorbidities: hypertension, diabetes mellitus. coronary artery disease, peripheral vascular disease. and cerebrovascular disease. Results. Subjects included 31 men and 15 women aged 22 to 87 years (mean +/- SD, 52 +/- 17). The mean gait speed for the group was 113.1 +/- 34.5 cm/s (low compared with norms established for persons of similar age). Results of multivariable regression showed that age, albumin, and Kt/V were important determinants of gait speed in this population. Overall, the model explained 52% of the variability in gait speed (r = 0.72, P < 0.0001). Qualitatively similar results were obtained using stair-climbing time or chair-rising time as the dependent variables. except that comorbidity was more important than age for stair climbing. The addition of physical activity level to the models did not eliminate the associations of albumin or Kt/V with physical performance. Conclusions. Physical performance is significantly impaired in ambulatory hemodialysis patients and is related to age, serum albumin, and dialysis dose. Prospective studies are needed to determine whether modification of dialysis dose or nutritional interventions can improve physical performance in patients on hemodialysis.