Longitudinal associations between air pollution and incident dementia as mediated by MRI-measured brain volumes in the UK Biobank
Background: Although there is increasing evidence that environmental exposures are associated with the risk of neurodegenerative conditions, there is still limited mechanistic evidence evaluating potential mediators in human populations. Methods: UK Biobank is a large long-term study of 500,000 adul...
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Elsevier
2025-01-01
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author | Rhiannon Thompson Xinning Tong Xueyi Shen Jinjun Ran Shengzhi Sun Xiaoxin Iris Yao Chen Shen |
author_facet | Rhiannon Thompson Xinning Tong Xueyi Shen Jinjun Ran Shengzhi Sun Xiaoxin Iris Yao Chen Shen |
author_sort | Rhiannon Thompson |
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description | Background: Although there is increasing evidence that environmental exposures are associated with the risk of neurodegenerative conditions, there is still limited mechanistic evidence evaluating potential mediators in human populations. Methods: UK Biobank is a large long-term study of 500,000 adults enrolled from 2006 to 2010 age 40–69 years. ICD-10 classified reports of dementia cases up to 2022 (Alzheimer’s disease, vascular dementia, dementia in other classified diseases, and unspecified dementia) were identified from health record linkage. Estimates of residential air pollution, traffic noise, and greenspace exposure have been modelled. Structural brain MRI was conducted from 2014 to 2022, with brain volumes relevant to dementia identified a priori. Associations between environmental exposures, brain volumes, and dementia cases (diagnosed post-MRI) were tested using linear and logistic regression and adjusted for age, sex, household income, ethnicity, education, smoking, and area-level deprivation. Mediation of exposure-outcome associations by plausible brain volumes (those associated with both environmental exposure and dementia outcomes) were modelled using the quasi-Bayesian Monte Carlo method (N = 34,817–39,772). Results: Small but significant mediating effects (2%-8% of relationships mediated) were observed between PM2.5abs exposure and dementia risk by reduced total brain volume, NOx and Alzheimer’s disease risk by reduced peripheral cortical grey matter, PM2.5abs and vascular dementia risk by reduced peripheral cortical grey matter, PM2.5abs and other dementia risk by reduced total grey matter, and PM10 and other dementia risk by reduced total grey matter. Greenspace and noise were not associated with dementia outcomes in the subset of the cohort providing brain imaging data. Conclusions: This study adds to existing evidence of associations between environmental exposures and dementia outcomes. Our findings provide novel evidence that differences in brain volume may mediate these relationships. Future research is required to prove this mechanism and establish the other mechanisms through which exposure to air pollution might increase dementia risk. |
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spelling | doaj-art-29c145d2b8794e1abde940712b4c036d2025-01-24T04:44:05ZengElsevierEnvironment International0160-41202025-01-01195109219Longitudinal associations between air pollution and incident dementia as mediated by MRI-measured brain volumes in the UK BiobankRhiannon Thompson0Xinning Tong1Xueyi Shen2Jinjun Ran3Shengzhi Sun4Xiaoxin Iris Yao5Chen Shen6National Institute for Health Research (NIHR) School for Public Health Research (NIHR SPHR), UK; MRC Centre for Environment and Health, Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, UKDepartment of Orthopaedics, The Eighth Affiliated Hospital, Sun Yat-Sen University, ChinaDivision of Psychiatry, Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UKSchool of Public Health, Shanghai Jiao Tong University School of Medicine, Shanghai, ChinaSchool of Public Health, Capital Medical University, Beijing, ChinaDepartment of Orthopaedics, The Eighth Affiliated Hospital, Sun Yat-Sen University, China; Department of Clinical Research, The Eighth Affiliated Hospital, Sun Yat-sen University, China; Corresponding author at: Department of Clinical Research, The Eighth Affiliated Hospital, Sun Yat-sen University, 3025 Shennan Road, Shenzhen 518033, China.MRC Centre for Environment and Health, Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, UK; National Institute for Health Research Health Protection Research Unit in Chemical and Radiation Threats and Hazards, School of Public Health, Imperial College London, UK; Corresponding author at: MRC Centre for Environment and Health, Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, 90 Wood Lane W12 0BZ, London, UK.Background: Although there is increasing evidence that environmental exposures are associated with the risk of neurodegenerative conditions, there is still limited mechanistic evidence evaluating potential mediators in human populations. Methods: UK Biobank is a large long-term study of 500,000 adults enrolled from 2006 to 2010 age 40–69 years. ICD-10 classified reports of dementia cases up to 2022 (Alzheimer’s disease, vascular dementia, dementia in other classified diseases, and unspecified dementia) were identified from health record linkage. Estimates of residential air pollution, traffic noise, and greenspace exposure have been modelled. Structural brain MRI was conducted from 2014 to 2022, with brain volumes relevant to dementia identified a priori. Associations between environmental exposures, brain volumes, and dementia cases (diagnosed post-MRI) were tested using linear and logistic regression and adjusted for age, sex, household income, ethnicity, education, smoking, and area-level deprivation. Mediation of exposure-outcome associations by plausible brain volumes (those associated with both environmental exposure and dementia outcomes) were modelled using the quasi-Bayesian Monte Carlo method (N = 34,817–39,772). Results: Small but significant mediating effects (2%-8% of relationships mediated) were observed between PM2.5abs exposure and dementia risk by reduced total brain volume, NOx and Alzheimer’s disease risk by reduced peripheral cortical grey matter, PM2.5abs and vascular dementia risk by reduced peripheral cortical grey matter, PM2.5abs and other dementia risk by reduced total grey matter, and PM10 and other dementia risk by reduced total grey matter. Greenspace and noise were not associated with dementia outcomes in the subset of the cohort providing brain imaging data. Conclusions: This study adds to existing evidence of associations between environmental exposures and dementia outcomes. Our findings provide novel evidence that differences in brain volume may mediate these relationships. Future research is required to prove this mechanism and establish the other mechanisms through which exposure to air pollution might increase dementia risk.http://www.sciencedirect.com/science/article/pii/S0160412024008067Air pollutionNoise pollutionGreenspaceDementiaAlzheimer’s diseaseMRI |
spellingShingle | Rhiannon Thompson Xinning Tong Xueyi Shen Jinjun Ran Shengzhi Sun Xiaoxin Iris Yao Chen Shen Longitudinal associations between air pollution and incident dementia as mediated by MRI-measured brain volumes in the UK Biobank Environment International Air pollution Noise pollution Greenspace Dementia Alzheimer’s disease MRI |
title | Longitudinal associations between air pollution and incident dementia as mediated by MRI-measured brain volumes in the UK Biobank |
title_full | Longitudinal associations between air pollution and incident dementia as mediated by MRI-measured brain volumes in the UK Biobank |
title_fullStr | Longitudinal associations between air pollution and incident dementia as mediated by MRI-measured brain volumes in the UK Biobank |
title_full_unstemmed | Longitudinal associations between air pollution and incident dementia as mediated by MRI-measured brain volumes in the UK Biobank |
title_short | Longitudinal associations between air pollution and incident dementia as mediated by MRI-measured brain volumes in the UK Biobank |
title_sort | longitudinal associations between air pollution and incident dementia as mediated by mri measured brain volumes in the uk biobank |
topic | Air pollution Noise pollution Greenspace Dementia Alzheimer’s disease MRI |
url | http://www.sciencedirect.com/science/article/pii/S0160412024008067 |
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