Simple nutritional indicators as independent predictors of mortality in hemodialysis patients

Abstract

A strong association exists between nutritional status and morbidity and mortality in patients with end-stage renal disease who are treated with hemodialysis. Described here is the predictive value for mortality over 5 years of follow-up of a number of risk factors, recorded at baseline, in a national sample of 3,607 hemodialysis patients. Among the variables studied were case-mix covariates, caregiver classifications of nutritional status, serum albumin concentration, and body mass index (BMI). The Case Mix Adequacy special study of the United States Renal Data System (USRDS) provided these measurements as of December 31, 1990. The USRDS patient standard analysis file provided follow-up data on mortality for all patients through December 31, 1995, by which time 64.7% of the patients had died. BMI is a simple anthropometric measurement that has received little attention in dialysis practice. Caregiver classification refers to documentation in a patient's dialysis facility medical records that stated an individual to be "undernourished/cachectic," "obese/overweight," or "well-nourished." The mean serum albumin was 3.7 +/- 0.45 (SD) g/dL, and the mean BMI was 24.4 +/- 5.3 (SD) kg/m2. By caregiver classification, 20.1% of patients were undernourished, and 24.9% obese. In hazard regression models, including but not limited to the Cox proportional hazards model, low BMI, low serum albumin, and the caregiver classification "undernourished" were independently and significantly predictive of increased mortality. In analyses allowing for time-varying relative mortality risks (ie, nonproportional hazards), the greatest predictive value of all three variables occurred early during follow-up, but the independent predictive value of baseline serum albumin and BMI measurements on mortality risk persisted even 5 years later. No evidence of increasing mortality risk was found for higher values of BMI. Serum albumin was confirmed to be a useful predictor of mortality risk in hemodialysis patients; BMI was established as an independently important predictor of mortality; both serum albumin and BMI, measured at baseline, continue to possess predictive value 5 years later; the subjective caregiver classification of nutritional status "undernourished" has independent value in predicting mortality risk beyond the information gained from two other markers of nutritional status--BMI and serum albumin.