Women are at greater risk of AD, although this may be partly explained by greater longevity,41 and there is evidence of sex differences in the relationships between risk factors and the development of dementia, including APOE ε4,41 lifestyle factors,41 and childhood intelligence,42 but the relevance of sex differences to the detection of subtle cognitive decline in preclinical AD is unclear. This evidence concerns the gene APOE and Alzheimer disease.