The A4 study : β-amyloid and cognition in 4432 cognitively unimpaired adults
Objective: To clarify the preclinical stage of Alzheimer’s disease by estimating when β-amyloid accumulation first becomes associated with changes in cognition. Methods: Here we studied a large group (N = 4432) of cognitively unimpaired individuals who were screened for inclusion in the A4 trial (age 65–85) to assess the effect of subthreshold levels of β-amyloid on cognition and to identify which
