APOE and Alzheimer disease: Importantly, in the three largest studies from this group, a study by Kleiman et al. that analyzed 366 patients with probable AD [21], a study by Farlow et al. that analyzed 374 placebo-treated AD clinical-trial participants [26], and a study by Aerssens et al. that analyzed 504 placebo-treated AD clinical-trial participants [27], the authors did not find any APOE4-associated differences in the rate of cognitive decline in AD.