Vintage, nutritional status, and survival in hemodialysis patients

Background. The link between dialysis "vintage" (length of time on dialysis in months to years) and survival has been difficult to define. largely bec ause of selection effects. Endstage renal disease (ESRD) is thought to be a wasting illness, but there are no published reports describing the associa tions between vintage and body composition in hemodialysis patients. Methods. We explored the relationships among vintage, nutritional status, a nd survival in a 3009 patient cohort of prevalent hemodialysis patients. Bo dy weight, total body water, body cell mass. and phase angle by bioelectric al impedance analysis were the body composition parameters of interest. We examined vintage as an explanatory variable in multiple linear regression a nalyses (adjusted for age, gender, race, and diabetes) using body compositi on parameters and biochemical indicators of nutritional status as dependent variables. Proportional hat ards regression was used to evaluate the assoc iation of vintage and survival with and without adjustment for case mix and laboratory variables. Results. Dialysis vintage was 3.8 +/- 3.7 (median 2.6) years. Body composit ion parameters tended to be lower after dialysis year 2. Linear estimates p er year of vintage beyond year 2 include -0.66 kg body wt (P < 0.0001) -0.1 7 kg total body water (P = 0.0003), -0.14 kg body cell mass (P < 0.0001). a nd -0.07 degrees phase angle (P < 0.0001). In unadjusted analyses, vintage was not associated with survival, either as a linear or higher order term. The adjustment for case mix yielded a vintage term associated with an incre ased relative risk (RR) of death (RR 1.04 (95% CI, 1.01 to 1.07 per year). A further adjustment for laboratory data yielded a RR df 1.06 (95% CI, 1.03 to 1.09 per year). Conclusion. Dialysis vintage is related to nutritional status in hemodialys is patients, with vintage of more than years associated with a significant decline in all measured nutritional parameters. Cross-sectional analyses pr obably underestimate these effects. A year accrued on dialysis is associate d with a 6% increase in the risk of death, all else equal. Longitudinal ass essments of nutritional status, including body composition, are required to better understand the natural history of wasting with ESRD and its implica tions for long-term survival.