Associations of neighborhood environment with brain imaging outcomes in the Australian Imaging, Biomarkers and Lifestyle cohort

Introduction: "Walkable" neighborhoods offer older adults opportunities for activities that may benefit cognition-related biological mechanisms. These have not previously been examined in this context. Methods: We objectively assessed neighborhood walkability for participants (n = 146) from the Australian Imaging, Biomarkers and Lifestyle study with apolipoprotein E (APOE) genotype and two 18-month-apart brain volumetric and/or amyloid beta burden assessments. Linear mixed models estimated associations of neighborhood walkability with levels and changes in brain imaging outcomes, the moderating effect of APOE epsilon 4 status, and the extent to which associations were explained by physical activity. Results: Cross-sectionally, neighborhood walkability was predictive of better neuroimaging outcomes except for left hippocampal volume. These associations were to a small extent explained by physical activity. APOE epsilon 4 carriers showed slower worsening of outcomes if living in walkable neighborhoods. Discussion: These findings indicate associations between neighborhood walkability and brain imaging measures (especially in APOE epsilon 4 carriers) minimally attributable to physical activity. (C) 2016 the Alzheimer's Association. Published by Elsevier Inc. All rights reserved.