Yang (34) found that RBC, Hb, HCT, MCHC, RDW-SD, and RDW-CV were all higher in the elderly hypertension group than in the control group (P < 0.05), suggesting that secondary erythrocytosis occurs in hypertensive patients and may induce an increase in blood viscosity. This evidence concerns the gene GSTM1 and Hypertension.