APOE and Mental deterioration: However, counterintuitively, the centenarians with lower and/or declined cognitive performance were less likely to have the APOE-ε4 allele compared with the centenarians who maintained high levels of cognitive functioning, suggesting that this latter group might be resilient to the risk-increasing effect of the APOE-ε4 allele on cognitive decline.12,42 Such resilience may be explained by, for example, an enrichment of protective genetic factors that counter the risk-increasing effect exerted by the APOE-ε4 allele.