Exposure to air pollution as a risk factor in the development of neurodegenerative diseases: a systematic review

Air pollution has emerged as a major environmental contributor to structural and functional brain changes. Following the 2020 PRISMA guidelines, this systematic review examined whether ambient air pollution exposure is associated with structural brain changes and cognitive alterations relevant to neurodegenerative processes. Additionally, it synthesizes the associated cognitive impact, identifying the most affected domains and the neuropsychological instruments used to assess them. A systematic search of PubMed and Scopus (last search: June/2026) identified studies published in English from 2016 onwards that included adults (≥18 years) without diagnosed neurological or psychiatric disorders at baseline, structural neuroimaging data, and measures of ambient air pollutant exposure. Findings were synthesized narratively to evaluate consistency across studies, and risk of bias was assessed using the Cochrane ROBINS-E tool. Twenty-nine studies met the inclusion criteria, with sample sizes ranging from 212 to 260,922 participants. Overall, evidence suggests that long-term exposure to air pollution is associated with structural brain changes and cognitive decline characteristic of AD and PD, with neuroinflammation and increased vascular risk acting as the primary underlying mechanisms. The most consistently reported alterations were observed in cortical and subcortical regions (including the neocortex, hippocampi, and nucleus accumbens) and white matter tracts (such as the splenium of the corpus callosum, inferior longitudinal fasciculus, and cingulum), alongside memory and language impairments. Although these findings support a potential neurotoxic effect of air pollution, which appears to be evident even at concentrations below current regulatory standards, longitudinal studies with standardized cognitive assessments and improved exposure measures are needed to strengthen causal inference. The review protocol was registered in PROSPERO (CRD420251180295).