APP and Alzheimer disease: In the same cohort, by adopting a candidate gene approach analysis in genes involved in AD, including APOE, APP, BDNF, PIN1, SNCA and TOMM40 [21], the authors observed that the average methylation levels of APOE and TOMM40 differed between presymptomatic and control groups, and confirmed no association between BDNF methylation and risk of developing dementia [21].