Association of physical activity with mortality in the US dialysis population

Background: It is unclear whether the protective benefits of regular physical activity on mortality extend to patients with end-stage renal disease (ESRD). We tested this hypothesis in a national cohort of new patients with ESRD in the United States. Methods: Data for a subset of patients (n = 2,507; 62%) from the Dialysis Morbidity and Mortality Wave 2 study were used to explore the associations of exercise and limitations in physical activity with mortality. Results: Overall, 56% of patients exercised less than once a week, whereas the remainder reported more frequent physical activity; 2 to 3 times/wk in 18%, 4 to 5 times/wk in 6%, and daily exercise in 20%. Severe limitations in vigorous and moderate physical activities were reported by 75% and 42%, respectively. Mortality risks were greatest for those with severe limitations in either moderate (relative risk [RR], 1.72; 95% confidence interval [CI], 1.44 to 2.05) or vigorous physical activities (RR, 1.51; 95% CI, 1.20 to 1.90) compared with those reporting minimal or no limitations. Conversely, mortality risks were lower for patients who exercised 2 to 3 (RR, 0.74; 95% CI, 0.58 to 0.95) or 4 to 5 times/wk (RR, 0.70; 95% CI, 0.47 to 1.07), whereas no advantage was associated with daily exercise (RR, 1.06; 95% CI, 0.86 to 1.30). Conclusion: Although limitations in physical activity are common among new patients with ESRD in the United States and correlate highly with increased mortality risk, this study shows an association of frequent exercise of up to 4 to 5 times/wk with improved survival. The surprising lack of association of daily exercise with increased survival deserves additional study.