Air Pollution and Incidence of Dementia: A Systematic Review and Meta-analysis

Ehsan Abolhasani; Vladimir Hachinski; Nargess Ghazaleh; Mahmoud Reza Azarpazhooh; Naghmeh Mokhber; Janet Martin

doi:10.1212/WNL.0000000000201419

Air Pollution and Incidence of Dementia: A Systematic Review and Meta-analysis

Neurology. 2023 Jan 10;100(2):e242-e254. doi: 10.1212/WNL.0000000000201419. Epub 2022 Oct 26.

Authors

Ehsan Abolhasani¹, Vladimir Hachinski¹, Nargess Ghazaleh¹, Mahmoud Reza Azarpazhooh¹, Naghmeh Mokhber¹, Janet Martin²

Affiliations

¹ From the Department of Epidemiology and Biostatistics (E.A., V.H., M.R.A., J.M), Clinical Neurological Sciences (V.H., M.R.A.), and Neuroscience Program (N.G.), Schulich School of Medicine and Dentistry, Western University, London, ON; Department of Psychiatry (N.M.), Schulich School of Medicine and Dentistry, University of Western Ontario, London; and Department of Anesthesia and Perioperative Medicine (J.M.), MEDICI Centre, Western University, London, ON, Canada.
² From the Department of Epidemiology and Biostatistics (E.A., V.H., M.R.A., J.M), Clinical Neurological Sciences (V.H., M.R.A.), and Neuroscience Program (N.G.), Schulich School of Medicine and Dentistry, Western University, London, ON; Department of Psychiatry (N.M.), Schulich School of Medicine and Dentistry, University of Western Ontario, London; and Department of Anesthesia and Perioperative Medicine (J.M.), MEDICI Centre, Western University, London, ON, Canada. jmarti83@uwo.ca.

PMID: 36288998
DOI: 10.1212/WNL.0000000000201419

Abstract

Background and objectives: Studies of association between air pollution and incidence of dementia have shown discrepant results. The aim of this study was to evaluate the association between air pollution and dementia.

Methods: In this systematic review and meta-analysis, PubMed, MEDLINE, EMBASE, PsycINFO, Scopus, and Web of Science were searched and updated in August 2021. Population-based cohort studies that reported on hazard ratio (HR) of dementia in association with exposure to fine particulate matter (PM_2·5), nitrogen oxides (NO_X), nitrogen dioxide (NO₂), or ozone (O₃) in those aged >40 years were included. Data were extracted by 2 independent investigators. The main outcome was the pooled HR for dementia per increment of pollutant, calculated using a random-effects model. Results were reported in accordance with PRISMA guidelines. The protocol was registered in PROSPERO (registration number: CRD42020219036).

Results: A total of 20 studies were included in the systematic review, and 17 provided data for the meta-analysis. The total included population was 91,391,296, with 5,521,111 (6%) being diagnosed with dementia. A total of 12, 5, 6, and 4 studies were included in the meta-analyses of PM_2·5, NO_X, NO₂, and O₃, respectively. The risk of dementia increased by 3% per 1 μg/m³ increment in PM_2·5 (HR, 1.03; 95% CI [1.02-1.05]; I² = 100%). The association between dementia per 10 μg/m³ increment in NO_X (HR, 1.05; 95% CI [0.99-1.13]; I² = 61%), NO₂ (HR, 1.03; 95% CI [1.00-1.07]; I² = 94%), and O₃ levels (HR, 1.01; 95% CI [0.91-1.11]; I² = 82%) was less clear, although a significant association could not be ruled out, and there was high heterogeneity across studies.

Discussion: Existing evidence suggests a significant association between exposure to PM_2·5 and incidence of dementia and nonsignificant association between dementia and NO_X, NO₂, and O₃ exposure. However, results should be interpreted in light of the small number of studies and high heterogeneity of effects across studies.

Publication types

Meta-Analysis
Systematic Review

MeSH terms

Air Pollutants* / adverse effects
Air Pollution* / adverse effects
Dementia* / epidemiology
Environmental Exposure
Humans
Incidence
Nitrogen Dioxide / analysis
Particulate Matter / adverse effects

Substances

Air Pollutants
Nitrogen Dioxide
Particulate Matter