Of relevance, our results demonstrate that PBMCs from MCI individuals exhibited elevated HDAC2 and HDAC3 levels, but no alterations were observed in AD patients already in the stage of dementia, suggesting that peripheral epigenetic dysregulation associated with histone acetylation imbalance occurs in early pre‐dementia phase of AD (MCI) where patients develop a pure memory deficit while preserving full autonomy. This evidence concerns the gene HDAC3 and dementia.