APOE and dementia: Our goal in the present study was to evaluate whether TBM would reveal early alterations in a cognitively asymptomatic midlife cohort enriched with APOE4 carriers from two large cohort studies, the PREVENT‐Dementia programme (UK‐Ireland) (Ritchie et al., 2013; Ritchie & Ritchie, 2012) and the ALFA (ALzheimer and FAmilies) (Molinuevo et al., 2016) study (Spain).