Specifically, two APOE-ε4 alleles carriers were at greatest risk of dementia followed by one-ε4 allele carriers compared with non-carriers, with an adjusted hazard ratio (HR) of 7.63 (95% confidence interval [CI] 6.46–9.01) and 2.47 (95% CI 2.22–2.76), respectively (Table 2). This evidence concerns the gene APOE and dementia.