APOE and dementia: Compared with the APOE‐ε allele combination 4/4, the 3/4 (β = ‐7.902, T = ‐1.022, p = 0.308) and 4/2 (β = ‐16.872, T = ‐1.911, p = 0.057) combinations were not associated with a significantly different trajectory of CSF Aβ1‐42 on approach of parental age of onset of dementia.