IL-6 Levels, Nutritional Status, and Mortality in Prevalent Hemodialysis Patients

Background and objectives The influence of serum IL-6 levels on nutritional status in chronic hemodialysis (HD) patients remains to be elucidated. The present report describes a prospective longitudinal study of IL-6 levels and nutritional parameters to determine whether high IL-6 levels are independently associated with nutritional status over time in a cohort of prevalent hemodialysis patients. Design, setting, participants, & measurements 85 clinically stable hemodialysis patients (37.6% women), with a mean age of 66.5 +/- 10.6 years, were studied after exclusion of patients with BMT < 20 kg/m(2) and/or serum albumin <35 g/L. IL-6, dietary energy and protein intake, and biochemical markers of nutrition and body composition (anthropometry and bioimpedance analysis) were measured at baseline and at 6, 12, 18, and 24 months following enrollment. Observation of this cohort was continued over 2 additional years. Results IL-6 levels increased with time in both unadjusted (linear estimate: 2.57 +/- 0.44 pg/ml per 2 yrs; P = 0.001) and adjusted models (linear estimate: 2.35 +/- 0.57 pg/ml per 2 yrs; P = 0.049). Significant reductions of daily energy intake, laboratory markers (albumin, transferrin, cholesterol, creatinine), and body composition (fat mass) with higher IL-6 levels were observed over the duration of the longitudinal observation period. However, none of the studied parameters were associated with changes in IL-6 levels over time (IL-6-by-time interactions were NS). Furthermore, cumulative incidences of survival were correlated with the baseline serum IL-6 levels (P = 0.004 by log-rank test). Finally, for each pg/ml increase in IL-6 level, the hazard ratio for death from all causes was 1.06 (95% CI 1.01 to 1.10) after adjustment for demographic and clinical parameters. Conclusions Our results suggest that higher serum IL-6 levels are associated with all-cause mortality without additional changes in clinical and laboratory markers of nutritional status in clinically stable HD patients. Clin J Am Soc Nephrol 6: 2253-2263, 2011. doi:10.2215/CJN.01770211