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 CKD patients 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: 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 (ISRCTN 87066351), a prospective observational mixed methods study of physical activity in patients with CKD. 450 CKD patients not requiring RRT, aged 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 GP Physical Activity Questionnaire (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 DASI was 0.51 (95% CI, 0.30-0.88) while a 1-unit increase in DASI was associated with SHR 0.97 (0.95-0.99). The adjusted SHRs of mortality were 0.48 (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 hours per week, 3 respectively, compared to no walking. Walking pace >3mph was associated with reduced risk of mortality [SHR 0.37 (0.20-0.71)] compared to walking pace <3mph. Conclusions: Physical function and walking behaviours were independently associated with survival in CKD and may help to identify patients at risk for adverse events.