Our examination of subgroups with the APOE ε4 gene revealed that educational levels (OR = 0.871, 95% confidence interval: 0.810–0.938, p < 0.001), BMI (OR = 0.913, 95% confidence interval: 0.847–0.985, p = 0.019), and tea consumption (OR = 0.548, 95% confidence interval: 0.339–0.886, p = 0.014) correlated with a reduced likelihood of MCI; age (OR = 1.145, 95% confidence interval: 1.061–1.236, p = 0.001) was linked to an increased risk of dementia, whereas hypertension (OR = 0.157, 95% confidence interval: 0.047–0.527, p = 0.003) correlated with a decreased risk of dementia. This evidence concerns the gene APOE and dementia.