The 200 cognitively unimpaired twins from whom blood samples and amyloid-β status were obtained as part of the EMIF-AD PreclinAD study were on average 70.5 years old, 57.5% was female, 33.5% carried at least one ApoE-ε4 allele and 16.5% showed amyloid-β pathology on PET/CSF. This evidence concerns the gene APOE and Alzheimer disease.