Interestingly, when we only include the studies that meet a conservative threshold of n > 100 AD patients, there are three studies that reported accelerated cognitive decline in APOE4+ vs. APOE4− AD patients [15–17], four that reported no difference [21, 23, 26, 27], and only one that reported slower cognitive decline in APOE4+ vs. APOE4− AD patients [30]. This evidence concerns the gene APOE and Alzheimer disease.