APOE and Mental deterioration: Furthermore, as clinical trials of drugs designed to reduce Aβ toxicity are typically conducted over intervals of 18-months [23,24], it is important to determine whether the ε4 exacerbation of Aβ related cognitive decline requires more than 18 months to become evident, or whether the absence of such effects in studies of this duration was related to the relatively small sample sizes studied did not provide sufficient statistical power to detect the interaction of apoe4 and amyloid on memory.