In addition, people of Tibetan have adapted to lower partial pressure of oxygen in the high altitude places and need not rely on increasing hemoglobin to supplement of oxygen.[10] Therefore, the adjustment values for Tibetan might be biased if we adjust the Hb concentrations only for altitude and take on account of difference of genetic background of Tibetan that make us overestimate the rate of anemia of Tibetan ethnic minority. Here, GSTM1 is linked to anemia (phenotype).