APOE and genetic risk variants influence Alzheimer's disease onset in carriers of an extra copy of APP, with and without Down syndrome.

An extra copy of the amyloid precursor protein (amyloid precursor protein) gene causes autosomal dominant Alzheimer's disease (AD) and AD in Down syndrome (down syndrome), but the factors underlying variability in age at onset (age at onset) remain unclear.

We investigated whether sporadic AD risk variants modify age at onset.