Dementia risk does not disappear after age 90. The number of people age 90 and older worldwide could reach about 230 million by 2100, yet this age group remains poorly represented in brain aging research. APOE2 is generally associated with lower Alzheimer’s risk, while APOE4 is the strongest common genetic risk factor for late-onset Alzheimer’s disease. “We saw evidence that APOE4 impacts males and females differently after age 90,” Colbeth said. “This has prompted us to look more closely at how APOE genotypes impact mortality among those with and without dementia by age 90.”