Association of physical activity with mortality in chronic kidney disease

Background: Chronic kidney disease (CKD) is an important risk factor for all-cause mortality. In the general population, physical activity is associated with reduced mortality. We examined the association of level of physical activity with mortality in patients with predominantly nondiabetic CKD stage 3-4. Methods: We studied 811 patients with CKD enrolled in the Modification of Diet in Renal Disease (MDRD) Study, a multicenter clinical trial conducted between 1989 and 1993. Patients completed a survey of their physical activity at baseline, from which we derived 3 physical activity variables: indoor activity, exercise and outdoor activity, using standardized scores. We used Cox proportional hazards modeling to examine the relationship between baseline physical activity and all-cause mortality with long-term outcome ascertained through 2000. Results: The mean age of the study population was 52 years, and 61% were male. The mean glomerular filtration rate was 32.5 ml/min per 1.73 m(2). A total of 24.6% died during follow-up. After adjustment for other factors significantly associated with mortality, the hazard ratio for all-cause mortality for indoor activity was 0.94 (95% confidence interval [ 95% CI], 0.77-1.14), exercise 1.01 (95% CI, 0.84-1.10) and outdoor activity 0.94 ( 95% CI, 0.80-1.10). Conclusions: Higher levels of physical activity were not significantly associated with a reduction in long-term mortality in patients with CKD in this cohort. Additional prospective studies are needed to confirm our finding and determine whether physical activity improves outcomes in patients with CKD.