CDKN2A and Alzheimer disease: Population (%) of Iba1+ microglia expressing p16INK4A increased in the BF of old 3xTgAD mice, which was significantly higher (39.48%) than that in younger AD mice (9.37%), P = 0.0007, also higher compared to age-matched WT mice (14.73%), P = 0.001, 2-tailed t-test with equal variance, n = 4–5 mice/group (Fig. 7D).