AR and posterior cortical atrophy: Earlier studies indicated that short CAG repeats (≤ 22) are more prevalent in African American males (75% with short alleles; median length, 18), less frequent in European-Americans (62% with short alleles; median length, 21), and least common in Asians-Americans (49% with short repeat alleles; median length, 22);[34] thus, an AR with shorter CAG repeat lengths is more prevalent in racial groups with higher PCa risk.