A potential limitation of this study is linked to blood collection performed in three different types of tubes: however when comparing cohorts of different age groups (young on heparin, middle aged on citrate and aged on heparin) we observed a linear correlation; moreover a low level of DYRK1A is observed in AD patients (on citrate) compared to aged controls (on heparin) and in DSAD patients (on EDTA) compared to DS patients (on EDTA) suggesting that DYRK1A changes associated with dementia are not caused by an effect of blood types of tube. This evidence concerns the gene DYRK1A and Alzheimer disease.