Changes in physical activity and risk of all-cause mortality in patients on maintence hemodialysis: a retrospective cohort study

BACKGROUND: A previous cohort study indicated a significant association of lower baseline level of physical activity in hemodialysis patients with elevated risks of mortality. However, there have been no reports regarding the association between changes in physical activity over time and mortality in hemodialysis patients. This study was performed to examine the prognostic significance of physical activity changes in hemodialysis patients. METHODS: This retrospective cohort study was performed in 192 hemodialysis patients with a 7-year follow-up. The average number of steps taken per non-dialysis day was used as a measure of physical activity. Forty (20.8%) patients had died during the follow-up period. The percentage change in physical activity between baseline and 12 months was determined, and patients were divided into three categories according to changes in physical activity. A decrease or increase in physical activity > 30% was defined as becoming less or more active, respectively, while decrease or increase in physical activity < 30% were classified as stable. RESULTS: Forty seven (24.5%), 51 (26.6%), and 94 (49.0%) patients were classified as becoming less active, becoming more active, and stable, respectively. The hazard ratio on multivariate analysis in patients with decreased physical activity was 3.68 (95% confidence interval, 1.55–8.78; P < 0.01) compared to those with increased physical activity. CONCLUSIONS: Reductions in physical activity were significantly associated with poor prognosis independent of not only patient characteristics but also baseline physical activity. Therefore, improved prognosis in hemodialysis patients requires means of preventing a decline in physical activity over time.