NfL blood levels increase early in DS‐AD, with baseline concentrations predicting dementia status and preceding amyloid PET changes by up to 10 years14, 15, 62, 63 while GFAP, rises significantly in prodromal and symptomatic DS‐AD, correlating well with imaging measures of AD (‐related) pathology.24 This evidence concerns the gene NEFL and Alzheimer disease.