Few studies have examined how the neighborhood's physical environment relates to cognition in older adults. Researchers categorized 4,716 individuals by apolipoprotein E (APOE) genotype -- a genetic risk factor for Alzheimer's disease (AD) to determine if there are cognitive benefits of living in neighborhoods with greater access to social, walking and retail destinations. Results showed that the positive influence of neighborhood environments on cognition are strongest among those who are at the lowest risk for AD, specifically APOE ?2 carriers.