Association of self-reported physical function with survival in patients with chronic kidney disease

Background: Reduced physical function is associated with an increased risk of mortality among patients with chronic kidney disease (CKD) not requiring renal replacement therapy (RRT). Assessments of physical performance can help to identify those at risk for adverse events. However, objective measures are not always feasible and self-reported measures may provide a suitable surrogate.

Methods: We performed a cohort study examining associations between self-reported physical function and walking behaviour with survival in patients with CKD not requiring RRT. Data were analysed from the QCKD study (Physical activity opinions in kidney disease) (ISRCTN 87066351), a prospective observational mixed methods study of physical activity in patients with CKD. A total of 450 patients with CKD not requiring RRT, ages 17-93 years, were followed up for a median of 43 months. Upon enrolment, participants completed two questionnaires: Duke Activity Status Index (DASI) (physical function) and General Practice Physical Activity Questionnaire (GPPAQ) (habitual activity). Mortality data were collected from electronic records in September 2016; RRT was considered a competing event.

Results: A total of 74 deaths occurred during follow-up and 101 participants were started on RRT. The adjusted subdistribution hazard ratio (SHR) of mortality in participants scoring >19.2 on the DASI was 0.51 [95% confidence interval (CI) 0.30-0.88] while a one-unit increase in the DASI was associated with an SHR of 0.97 (95% CI 0.95-0.99). The adjusted SHRs of mortality were 0.48 (95% CI 0.26-0.90), 0.25 (0.11-0.57) and 0.48 (0.23-0.80) for participants walking <1, 1-3 and ≥3 h/week, respectively, compared with no walking. A walking pace >3 mph was associated with a reduced risk of mortality [SHR 0.37 (95% CI 0.20-0.71)] compared with a walking pace <3 mph.

Conclusions: Physical function and walking behaviours were independently associated with survival in CKD and may help to identify patients at risk for adverse events.