Patients without the apolipoprotein E4 allele (APOE e4), being a factor contributing to AD development, but with the allele T of the -1562C/T polymorphism in the MMP-9 gene were at a lower risk of dementia development when compared to carriers of the allele C [OR = 0.6 (95% CI, 0.3–1.0), p = 0.05] (Helbecque et al., 2003). This evidence concerns the gene MMP9 and dementia.