Age and anemia management: relationship of hemoglobin levels with mortality might differ between elderly and nonelderly hemodialysis patients

The elderly hemodialyzed population is growing. However, little is known about the relationship between hemoglobin level and survival according to age. We investigated the effect of age on the relationship between hemoglobin and survival within the Japan Dialysis Outcomes and Practice Patterns Study (DOPPS) cohort. We enrolled the entire Japan DOPPS phases 3 and 4 population. Patients were divided by the age of 75 years into two groups. Cox's proportional hazard model was used with hemoglobin at every 4 months treated as a time-dependent variable. The interaction of age and hemoglobin was analyzed. We included 3341 patients in the analyses. The primary outcome occurred in 567 patients during the median follow-up of 2.64 years. Hemoglobin of entire population was 10.3 +/- 1.3 g/dL. The median of epoetin dose was 3000 IU/week. Interaction was found between ages stratified by the age of 75 years and hemoglobin values (P = 0.045) with use of Cox's proportional hazard model. The nonelderly population had poorer prognosis with hemoglobin < 10 g/dL, while elderly population only with hemoglobin < 9 g/dL. For both hemoglobin strata < 9, a parts per thousand yen9 and < 10 g/dL, interactions between age and hemoglobin were significant. Subgroup analysis indicated that interaction between age and Hb levels was observed only in the nondiabetic nephropathy group. Several sensitivity analyses demonstrated a similar trend with the original analyses and reinforced the robustness. The elderly population might tolerate low hemoglobin levels. Our findings open the way for further investigation of individualized anemia management.