Neighborhood Attributes and Cognitive Function in Older Adults

Abstract

Background: Neighborhood environments are a potential modifiable factor for improving cognitive function among older adults by providing opportunities for physical activity and destinations for social interaction. Lifestyle factors enhance resilience to the development of brain pathology. However, the impact of neighborhoods on cognitive function and its mechanism among older adults is inconclusive. Objectives: This dissertation consists of three studies. The aim of the first study was to determine the association of objective neighborhood attributes (land-use mix, residential density, intersection density, presence of trails, sidewalk coverage, gradient of walkways, and areas covered by parks) with decline in cognitive function over a 2-year period among older adults. The aim of the second study was to examine the associations of perceived neighborhood attributes (residential density, land-use mix, transit ace\ss, bicycling infrastructure, recreation facilities, sidewalk coverage, crime safety, traffic safety, and physically active neighbors) with cognitive function among older adults. The aim of the third study was to test a mediating role of walking on the association between objective walkability and cognitive function or perceived walkability and cognitive function among older adults. Research Design: This dissertation employed a secondary data analysis method using the Adult Changes in Thought (ACT) study, a prospective cohort study. Data on neighborhood characteristics from 2016 King County Assessor, 2016 US Census TIGER/Line road, King County Geographic Information Systems Center, UW Urban Form Lab, and USGS digital elevation raster model (DEM) were combined with the ACT dataset. The first study was a longitudinal analysis in a sample of 1,302 older adults living in King County. Change in cognitive function was measured over 2 years by the Cognitive Ability Screening Instrument (CASI). Objective neighborhood attributes (land-use mix, residential density, intersection density, presence of trail, presence of sidewalk, gradient of walkways, and park area) were measured by geographic information systems (GIS). Multivariate linear regression models were fitted. The second study was a cross-sectional analysis in 821 adults aged 65 or older. Perceived neighborhood attributes were measured by the Physical Activity Neighborhood Environment Scale (PANE). The associations were tested using linear regression. The third study was a cross-sectional analysis in 799 older adults for the associations between objective walkability and cognitive function and in 680 older adults for the associations between perceived walkability and cognitive function. Walking was measured using an accelerometer. Associations were tested using linear regression. Indirect effects were tested using causal mediation analysis. Results: The first study found that greater objective park area within an 800 m buffer was associated with positive change in cognitive function. However, the effect size was small. Other objective neighborhood attributes were not associated with cognitive function change. The second study found that greater perceived access to public transit was associated with better cognitive function, and greater perceived sidewalk coverage was also related to better cognitive function. Perceived land use-mix and recreational facilities, crime, safety, safety from traffic, and neighbors physically active were associated with cognitive function in only unadjusted models. The third study revealed that walking had an indirect effect on the association between perceived walkability and cognitive function but not on the association between objective walkability and cognitive function. Conclusions: Strategies targeting both environmental factors as well as individual behavioral factors should be considered to improve cognitive function in older adults. Improving the perception of neighborhood attributes alongside modifying physical infrastructure may positively impact cognitive function in older adults. Modifying neighborhood infrastructure may not be sufficient to improve perceived walkability. Educational and social support programs are required to improve perceived walkability. The improved perceived walkability may encourage older adults to be more physically active and the benefits of physical activity may improve cognitive function in older adults.