The main aims of the present study based on the Vantaa 85+ cohort are to develop multifactorial models for (1) predicting incident dementia in the oldest old, considering sociodemographic, cognitive, clinical, lifestyle, and apolipoprotein E (APOE) genotype data; and (2) predicting dementia-related neuropathologies at death in the oldest old, including Alzheimer’s disease (AD)-related pathology (amyloid plaques and neurofibrillary tangles), cerebral amyloid angiopathy (CAA), cerebral macro- and microinfarcts, and Lewy body pathology (α-synuclein). The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.