Subsequently, the analysis of TOMM40’650 SNP showed that in AD patients with A/A genotype the level of Hcy was significantly increased (p<0.01 vs. UC and RC), while GSH/Hcy ratio (p<0.001 vs. UC and p<0.01 vs. RC), 8-oxo2dG (p<0.05 vs. UC and p<0.001 vs. RC) and 8-oxo2dG/OGG1 ratio (p<0.01 vs. UC and RC) were significantly reduced, as compared to controls with the same genotype, regardless of family history of AD. Here, OGG1 is linked to Alzheimer disease.