Environmental Exposures and Brain Magnetic Resonance Imaging Phenotypes in Cognitively Healthy Ageing: A Systematic Review
Abstract
Background: Air pollution and built environment features are increasingly associated with negative health outcomes, yet their relation to brain health in cognitively healthy older adults remains unclear.
Methods: To synthesise the extant literature, we conducted a systematic review, searching MEDLINE (PubMed) and Web of Science (Core Collection) from inception to February 23, 2026. Eligible studies assessed a natural or built environmental exposure against brain magnetic resonance imaging (MRI) measures in cognitively healthy older adults (ages 65+). Reviewers screened and extracted summary data from published reports in Covidence; no individual patient data were sought. The main outcome was brain health; findings were synthesised narratively using an effect-direction approach, as heterogeneous exposures, outcomes, and effect metrics precluded pooling.
Findings: Of 2,496 records screened, 27 studies met eligibility, comprising >84,000 older adults across 10 countries: United States, South Korea, United Kingdom, France, Spain, Sweden, Netherlands, Taiwan, Germany, and Japan. Thirteen studies were cross-sectional and 14 were cohort studies (nine observational and five longitudinal). Higher air pollution exposure—particularly PM2.5, NO2, and PM10—was associated with altered brain structure: smaller total, grey matter, and white matter volumes, greater white matter hyperintensities, cortical thinning, and smaller medial temporal and hippocampal volumes; greenspace was associated with more favourable brain structure in several mostly cross-sectional studies, though findings were not uniform. Thirteen studies met criteria for high methodological quality and low though not uniform risk of bias; outcome assessment was a recurring source of bias (12 of 27 studies), and four of the five longitudinal studies did not meet criterion for follow-up adequacy.
Interpretation: This review synthesises emerging observational evidence that air pollution is associated with differences in brain structure in cognitively healthy ageing. Because the included evidence is predominantly cross-sectional, these associations are hypothesis generating; if confirmed in longitudinal studies, this modifiable exposure could serve as a potential target for policymakers aiming to protect brain health in the fastest growing segment of the global population.
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BibTeX
@misc{perry2026environmental,
title = {{Environmental Exposures and Brain Magnetic Resonance Imaging Phenotypes in Cognitively Healthy Ageing: A Systematic Review}},
author = {Kelly E Perry and Breanna Marie Watterson and Jenna Louise Merenstein},
howpublished = {PsyArXiv},
year = {2026},
month = nov,
doi = {10.31234/osf.io/yj7xw_v2},
url = {https://osf.io/preprints/psyarxiv/yj7xw_v2/},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Environmental Exposures and Brain Magnetic Resonance Imaging Phenotypes in Cognitively Healthy Ageing: A Systematic Review
AU - Kelly E Perry
AU - Breanna Marie Watterson
AU - Jenna Louise Merenstein
PY - 2026
DA - 2026/11/12
PB - PsyArXiv
DO - 10.31234/osf.io/yj7xw_v2
UR - https://osf.io/preprints/psyarxiv/yj7xw_v2/
AB - Background: Air pollution and built environment features are increasingly associated with negative health outcomes, yet their relation to brain health in cognitively healthy older adults remains unclear. Methods: To synthesise the extant literature, we conducted a systematic review, searching MEDLINE (PubMed) and Web of Science (Core Collection) from inception to February 23, 2026. Eligible studies assessed a natural or built environmental exposure against brain magnetic resonance imaging (MRI) measures in cognitively healthy older adults (ages 65+). Reviewers screened and extracted summary data from published reports in Covidence; no individual patient data were sought. The main outcome was brain health; findings were synthesised narratively using an effect-direction approach, as heterogeneous exposures, outcomes, and effect metrics precluded pooling. Findings: Of 2,496 records screened, 27 studies met eligibility, comprising >84,000 older adults across 10 countries: United States, South Korea, United Kingdom, France, Spain, Sweden, Netherlands, Taiwan, Germany, and Japan. Thirteen studies were cross-sectional and 14 were cohort studies (nine observational and five longitudinal). Higher air pollution exposure—particularly PM2.5, NO2, and PM10—was associated with altered brain structure: smaller total, grey matter, and white matter volumes, greater white matter hyperintensities, cortical thinning, and smaller medial temporal and hippocampal volumes; greenspace was associated with more favourable brain structure in several mostly cross-sectional studies, though findings were not uniform. Thirteen studies met criteria for high methodological quality and low though not uniform risk of bias; outcome assessment was a recurring source of bias (12 of 27 studies), and four of the five longitudinal studies did not meet criterion for follow-up adequacy. Interpretation: This review synthesises emerging observational evidence that air pollution is associated with differences in brain structure in cognitively healthy ageing. Because the included evidence is predominantly cross-sectional, these associations are hypothesis generating; if confirmed in longitudinal studies, this modifiable exposure could serve as a potential target for policymakers aiming to protect brain health in the fastest growing segment of the global population.
ER -