# Neighborhood Greenspace in Midlife and Late-Life Brain Imaging Outcomes: Multi-Ethnic Study of Atherosclerosis

## TL;DR

Living in greener neighborhoods during midlife may be linked to better brain health in later life, potentially reducing Alzheimer's risk.

## Contribution

New evidence linking midlife greenspace exposure to late-life brain volume in Alzheimer's-prone regions.

## Key findings

- Greater midlife greenness correlates with increased late-life gray matter volume in Alzheimer's regions.
- Open/park space, but not tree canopy, was associated with better brain outcomes.
- Associations remained after adjusting for socioeconomic and health factors.

## Abstract

We investigated associations between residential neighborhood greenspace in midlife and late-life magnetic resonance imaging (MRI) outcomes. We used data on 1,141 participants without dementia in the Multi-Ethnic Study of Atherosclerosis (MESA), restricting to those with address history covering midlife. Geocoded addresses (1980-2009) were used to derive midlife residential greenness using annual (summer:∼July 1) normalized difference vegetation index (NDVI) values from LANDSAT satellite imagery (range=0-1, closer to 1=greener) and annual values of % tree canopy and open/park space linearly interpolated from 2001-2011 National Land Cover Datasets. We calculated 10-year mean neighborhood greenspace values spanning midlife (45-54 years). MRI measures included hippocampal and white matter hyperintensity volumes and total gray matter volume (GMV) in Alzheimer’s disease (AD) prone regions of interest (ROI), which accounted for head size differences (e.g., (hippocampal volume/intracranial volume) x 100%). Multivariable linear regression estimated associations between midlife 10-year mean greenspace measures and later-life MRI outcomes, controlling for site, demographics (e.g., age, ethnoracial group, gender, education), neighborhood socioeconomic status, and comorbidities (e.g., hypertension, diabetes), measured at the time of MRI. Participants were 70.1±6 years old at MRI and 54% were women. Greater midlife residential greenness and % open/park space (but not % tree canopy) were associated with greater late-life GMV (%) in AD ROI (estimates per interquartile range (IQR), respectively=0.09, 95% CI = 0.04-0.14; estimate=0.09, 95% CI = 0.05-0.12). In a diverse US cohort, individuals living in greener neighborhoods in midlife exhibited greater late-life GMV (%) in AD ROI, possibly leading to a small reduction in AD risk that should be explored further.