Age-related or late-life dementia is characterized by neurodegeneration induced by the accumulation of amyloid plaques and neurofibrillary tangles, and by several overlapping features, including vascular risk factors (e.g., hypertension, diabetes mellitus, and obesity), cerebrovascular diseases, inflammation, and apolipoprotein E (APOE) genotypes. The gene discussed is APOE; the disease is obesity due to melanocortin 4 receptor deficiency.