Other well-known risk factors are the APOE-ε2 and APOE-ε4 alleles, which are known to have protective and risk-increasing effects, respectively, on cognitive decline and dementia.27,28,29 The prevalence of the protective APOE-ε2 allele was similar in centenarians who maintained high levels of cognitive functioning and those with lower and/or declined cognitive performance. Here, APOE is linked to dementia.