CDKN2A and Alzheimer disease: The average Rp on colocalization of Iba1 and p16INK4A within ROI of BF was significantly higher in old AD mice (Rp = 0.58) versus in old WT mice (Rp = 0.28) as well, P < 0.0001, and higher versus in younger AD mice (Rp = 0.12), P < 0.0001 (Fig. 7E).