Physical Activity and Mortality in Chronic Kidney Disease (NHANES III)

Abstract

Background and objectives: Chronic kidney disease (CKD) is associated with impaired physical activity. However, it is unclear whether the associations of physical activity with mortality are modified by the presence of CKD. Therefore, we examined the effects of CKD on the associations of physical activity with mortality. Design, setting, participants, & measurements: This was an observational study of 15,368 adult participants in the National Health and Nutrition Examination Survey III; 5.9% had CKD (eGFR < 60 ml/min per 1.73 m²). Based on the frequency and intensity of leisure time physical activity obtained by a questionnaire, participants were divided into inactive, insufficiently active, and active groups. Time to mortality was examined in Cox models, taking into account the complex survey design. Results: Inactivity was present in 13.5% of the non-CKD and 28.0% of the CKD groups (P < 0.001). In two separate multivariable Cox models, compared with the physically inactive group, hazard ratios (95% confidence intervals) of mortality for insufficiently active and active groups were 0.60 (0.45 to 0.81) and 0.59 (0.45 to 0.77) in the non-CKD subpopulation and 0.58 (0.42 to 0.79) and 0.44 (0.33 to 0.58) in the CKD subpopulation. These hazard ratios did not differ significantly between the CKD and non-CKD subpopulations (P > 0.3). Conclusions: Physical inactivity is associated with increased mortality in CKD and non-CKD populations. As in the non-CKD population, increased physical activity might have a survival benefit in the CKD population.