APOE and Alzheimer disease: Our results also reveal that APOE ε3 and APOE ε4 heterozygotes show an intermediate OR value (OR = 3.43; 95%CI [2.95–3.99], p < 0.0001) between APOE ε3 (OR = 0.47; 95% CI [0.33–0.67], p < 0.0001) and APOE ε4 homozygotes (OR = 7.08; 95% CI [4.22–11.86], p < 0.0001), suggesting a dose-dependent association among the number of APOE ε4 alleles and the risk of AD in the Italian population.