Association of physical activity with survival among ambulatory patients on dialysis: the Comprehensive Dialysis Study

Abstract

Background and objectives: Despite high mortality and low levels of physical activity (PA) among patients starting dialysis, the link between low PA and mortality has not been carefully evaluated.

Design, setting, participants, & measurements: The Comprehensive Dialysis Study was a prospective cohort study that enrolled patients who started dialysis between June 2005 and June 2007 in a random sample of dialysis facilities in the United States. The Human Activity Profile (HAP) was administered to estimate PA among 1554 ambulatory enrolled patients in the Comprehensive Dialysis Study. Patients were followed until death or September 30, 2009, and the major outcome was all-cause mortality.

Results: The average age was 59.8 (14.2) years; 55% of participants were male, 28% were black, and 56% had diabetes mellitus. The majority (57.3%) had low fitness estimated from the HAP score. The median follow-up was 2.6 (interquartile range, 2.2-3.1) years. The association between PA and mortality was linear across the range of scores (1-94). After multivariable adjustment, lower adjusted activity score on the HAP was associated with higher mortality (hazard ratio, 1.30; 95% confidence interval, 1.23-1.39 per 10 points). Patients in the lowest level of fitness experienced a 3.5-fold (95% confidence interval, 2.54-4.89) increase in risk of death compared with those with average or above fitness.

Conclusions: Low levels of PA are strongly associated with mortality among patients new to dialysis. Interventions aimed to preserve or enhance PA should be prospectively tested.

Figure 1.

Kaplan–Meier plots showing survival. (A) Kaplan–Meier plot showing survival by fitness category, estimated using the adjusted activity scale (AAS) of the Human Activity Profile. The solid line represents the low fitness group, the dotted line the fair fitness group, and the dashed line the group with average or above fitness. (B) Kaplan-Meier plot showing survival by tertiles within the low fitness category. The solid line represents the extremely low tertile, the dotted line the very low tertile, and the dashed line the low tertile.