Logistic regression was performed to investigate the role of the APOE ε4 allele as a possible confounder, with the different types of dementia compared to controls as dependent variables and the described ABCB1 SNPs (as wild-type, heterozygous and homozygous mutants) and APOE (as ε4 allele carriers vs. non-carriers) as independent variables. The gene discussed is APOE; the disease is dementia.