Figure 1. Distribution of patient population according to patient age.

Of the 5,244 subjects included in the Clinical Research Center for end-stage renal disease (CRC-ESRD) registry, 1,835 subjects were excluded due to lack of information regarding age or hemoglobin (Hb) concentration. Therefore, 3,409 patients were included: 488 were younger than 40 years of age, 1,650 were between 40 and 60 years of age, and 1,271 were 60 years of age or older.