We hypothesized that individuals with higher composite CR may have a lower risk of transition from normal cognitive function through prodromal dementia to clinical dementia or death, and a higher risk of transition from prodromal dementia to normal cognitive function and that the transitions would be independent of neuropathological markers and more prominent among the APOE‐ɛ4 allele carriers than noncarriers. This evidence concerns the gene APOE and dementia.