Therefore, our current investigation studies larger cohorts in memory clinic settings, mainly aimed to (1) investigate the distribution characteristics of APOE ε4 alleles in different demography and cognitive impairment groups diagnosed based on updated criteria (SCD-I) (Jessen et al., 2014) and Jak-Bondi (Edmonds et al., 2015); (2) analyze the association of APOE ε4 and scores of SCD-Q9 reflecting cognitive impairment; and (3) assess the discriminatory powers of APOE ε4 alleles themselves and their combination with scores of SCD-Q9 for diagnosing cognitive impairment. The gene discussed is APOE; the disease is Cognitive impairment.