Role of nutritional status and inflammation in higher survival of African American and Hispanic hemodialysis patients

Background: Observational studies indicate greater survival in African American and Hispanic maintenance hemodialysis patients compared with their non-Hispanic white counterparts, although African Americans have shorter life expectancy than whites in the general population. We hypothesized that this apparent survival advantage is due to a more favorable nutritional/inflammatory profile in minority hemodialysis patients.

Study design: We examined the association between race/ethnicity and 5-year survival before and after adjustment for case-mix and surrogates of the malnutrition-inflammation complex syndrome (MICS) using Cox regression with or without matched sampling in a large cohort of adult hemodialysis patients.

Setting & participants: 124,029 adult hemodialysis patients, including 16% Hispanics, 49% non-Hispanic whites, and 35% African Americans.

Predictors: Race/ethnicity before and after adjustment for MICS, including values for body mass index, serum albumin, total iron-binding capacity, ferritin, creatinine, phosphorus, calcium, bicarbonate, white blood cell count, lymphocyte percentage, hemoglobin, and protein intake.

Outcomes: 5-year (July 2001 to June 2006) survival.

Results: In dialysis patients, blacks and Hispanics had lower mortality overall than non-Hispanic whites after traditional case-mix adjustment. However, after additional control for MICS, Hispanics had mortality similar to non-Hispanic whites, and African Americans had even higher mortality. Unadjusted, case-mix-, and MICS-adjusted HRs for African Americans versus whites were 0.68 (95% CI, 0.66-0.69), 0.89 (95% CI, 0.86-0.91), and 1.06 (95% CI, 1.03-1.09) in the unmatched cohort and, 0.95 (95% CI, 0.90-0.99), 0.89 (95% CI, 0.84-0.94), and 1.16 (95% CI, 1.07-1.26) in the matched cohort, and for Hispanics versus whites, 0.66 (95% CI, 0.64-0.69), 0.84 (95% CI, 0.81-0.87), and 0.97 (95% CI, 0.94-1.00) in the unmatched cohort and 0.89 (95% CI, 0.84-0.95), 0.88 (95% CI, 0.83-0.95), and 0.98 (95% CI, 0.91-1.06) in the matched cohort, respectively.

Limitations: Adjustment cannot be made for unmeasured confounders.

Conclusions: Survival advantages of African American and Hispanic hemodialysis patients may be related to differences in nutritional and inflammatory status. Further studies are required to explore these differences.