APOE and Dravet syndrome: In 464 adults with DS from the Cambridge Dementia in Down's Syndrome (DiDS) cohort and DABNI, adults with DS who were APOE ε4 carriers had a lower CSF ratio of Aβ1‐42/Aβ1‐40 in young adulthood, earlier increases in amyloid PET and plasma p‐tau181 levels, earlier reductions in cortical metabolism and hippocampal volume, and earlier memory decline than non‐carriers.40