Hemoglobin A1c and Survival in Maintenance Hemodialysis Patients

Abstract

Objective: The optimal target for glycemic control has not been established in diabetic dialysis patients.

Research Design and Methods: To address this question, the national database of a large dialysis organization (DaVita) was analyzed via time-dependent survival models with repeated measures.

Results: Of 82,933 patients undergoing maintenance hemodialysis (MHD) in DaVita outpatient clinics over 3 yrs (7/01-6/04), 23,618 diabetic MHD patients had hemoglobin A1c (HbA1c) measurements at least once. Unadjusted survival analyses indicated paradoxically lower death hazard ratios (HR) with higher HbA1c values. However, after adjusting for potential confounders (demographics, dialysis vintage and dose, comorbidity, anemia and surrogates of malnutrition and inflammation), higher HbA1c values were incrementally associated with higher death risks. Compared to HbA1c in 5-6% range, the adjusted all-cause and cardiovascular death HR for HbA1c≥10% was 1.41 (95% confidence interval [CI]: 1.25-1.60) and 1.73 (95%CI: 1.44-2.08), respectively (p<0.001). The incremental increase in death risk for rising HbA1c values was monotonic and robust in non-anemic patients (Hb>11.0 g/dL). In subgroup analyses, the association between HbA1c>6% and increased death risk was more prominent among younger patients, those who had undergone dialysis >2 yrs, and those with higher protein intake (>1 gm/kg/day), blood hemoglobin (>11 g/dl) or serum ferritin values (>500 ng/ml).

Conclusions: In diabetic MHD patients, the apparently counterintuitive association between poor glycemic control and greater survival is explained by such confounders as malnutrition and anemia. . All things equal, higher HbA1c is associated with increased death risk. Lower HbA1c levels not related to malnutrition or anemia appears associated with improved survival in MHD patients.