Lack of Exercise Linked to Increased Mortality in Chronic Kidney Disease
By Laurie Barclay, MD
Medscape Medical News
October 19, 2009 — Lack of exercise is linked to increased mortality rates in chronic kidney disease (CKD), according to the results of an observational study reported in the October 9 Online First issue of the Clinical Journal of the American Society of Nephrology.
"...CKD is associated with impaired physical activity," write Srinivasan Beddhu, MD, from Salt Lake City VA Healthcare System and University of Utah, and colleagues. "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."
The study cohort consisted of 15,368 adults enrolled in the National Health and Nutrition Examination Survey III, of whom 5.9% had CKD, defined as an estimated glomerular filtration rate of less than 60 mL/minute/1.73 m2. A questionnaire regarding frequency and intensity of leisure time physical activity allowed categorizing the participants into inactive, insufficiently active, and active groups. Cox models were used to determine time to mortality. Average duration of follow-up was 7 to 9 years.
Of the non-CKD participants, 13.5% were inactive vs 28.0% of the CKD groups (P < .001). Compared with the physically inactive group, the insufficiently active and active groups had hazard ratios (HRs) of mortality of 0.60 (95% confidence interval [CI], 0.45 - 0.81) and 0.59 (95% CI, 0.45 - 0.77) in the non-CKD subpopulation and 0.58 (95% CI, 0.42 - 0.79) and 0.44 (95% CI, 0.33 - 0.58) in the CKD subpopulation, respectively, in 2 separate multivariable Cox models. These HRs were not statistically significantly different between the CKD and non-CKD subpopulations (P > .3).
Limitations of this study include observational design using existing data, possible unmeasured residual confounding, and self-reported physical activities.
"Physical inactivity is associated with increased mortality in CKD and non-CKD populations," the study authors write. "As in the non-CKD population, increased physical activity might have a survival benefit in the CKD population....This is particularly important as most patients with stage III CKD die before they develop end stage renal disease."
The Dialysis Research Foundation of Utah supported this study. The study authors have disclosed no relevant financial relationships.
Clin J Am Soc Nephrol. Published online October 9, 2009.