APOE and dementia: Splitting by APOE4 status in NACC (which contains most of the APOE4 homozygote data) using the APCC, PACC, and RBANS proxies showed that the shape of the curve did not seem to depend much on the genotype if anchored at the time of diagnosis, with a steep decline in cognition occurring 2–4 years prior to the manifestation of dementia (Additional file 1: Fig. S1).