New research shows that air pollution, especially PM2.5, may contribute to brain atrophy but does not appear to harm cognitive function. Urbanization affects the strength of this connection.
Study: Association of air pollution with cognitive functioning and markers of structural brain damage: the Maastricht study. Image credits: frank_kie / Shutterstock
This is evident from a recent study published in the journal Environment International, researchers examined the possible relationship between exposure to different types of air pollutants and brain structure and cognitive function in middle-aged and older adults. They found that high exposure to fine particles with a diameter of less than 2.5 micrometers (PM2.5) was associated with lower gray matter and higher cerebrospinal fluid volumes, indicative of cerebral atrophy, with stronger effects in men on white matter volume.
However, these associations became non-significant after adjusting for urbanization. They found no significant association with cognitive function or most brain markers, although curvilinear associations between PM2.5 and brain volumes were observed, with exposure to medium to high frequencies associated with greater cerebral atrophy.
Background
Dementia is a progressive condition characterized by a decline in cognitive functions such as memory, attention and planning, usually caused by Alzheimer’s disease and cerebrovascular problems.
The global incidence of dementia is expected to triple by 2050, putting pressure on healthcare systems and increasing healthcare burdens. While adaptive lifestyle and cardiovascular factors are known to contribute to dementia risk, shared environmental factors such as air pollution also emerge as major contributors.
Air pollution, especially PM2.5has been linked to neuroinflammation and cognitive decline, potentially affecting brain structure by reducing gray matter and causing other forms of cerebral atrophy. Recent studies show that air pollution may increase the risk of dementia more than other factors such as high blood pressure or diabetes, but most research has focused on individual pollutants and linear associations.
Further research, particularly using brain imaging in addition to cognitive assessments, is needed to understand the non-linear effects of air pollution on brain health and cognitive decline. Therefore, in the current study, researchers examined the relationship between air pollution, cognitive performance, and brain structure in older adults, while accounting for demographic and modifiable risk factors for dementia.
About the study
Researchers obtained data from the Maastricht study, a population-based cohort focused on the etiology and complications of type 2 diabetes (T2DM) among adults aged 40-75 years in the South of the Netherlands. Participants were recruited through media and registries, and those with missing data were excluded. A total of 4,002 adults were included. The average age was 59.2 years and 49.2% of them were male.
Exposure to ambient air pollution was assessed using data from the Geoscience and Health Cohort Consortium (GECCO) using local and national models for pollutants such as PM2.5P.M10soot, and NO2assigned to participants’ postal addresses.
Cognitive functioning was evaluated using standardized neuropsychological tests, while magnetic resonance imaging (MRI) scans were used to assess structural brain markers such as gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) volume.
Risk factors for dementia were summarized using the Lifestyle for Brain Health (LIBRA) score. Socio-economic position was evaluated using education, occupation and family income. Statistical analysis included the use of Ttests, chi-square tests, multiple linear regression, binary logistic regression, likelihood ratio tests and sensitivity analysis.
Results and discussion
Increased PM2.5 Exposures were observed throughout the study area, with minimal variation in exposure levels. Excluded participants were older, had lower SEP, higher prevalence of T2DM and were more likely to be men. They were exposed to higher levels of air pollution with higher LIBRA scores, smaller GM and WM volumes, larger CSF and WMH volumes and lower cognitive performance in overall cognition, memory, processing speed and executive functions.
The study found no significant linear associations between exposure to air pollution (PM2.5P.M10NO2and soot) and cognitive function, cognitive domains or volumetric markers of the brain (GM, WM, CSF, WM hyperintensity). However, curvilinear relationships were found between PM2.5 and GM/CSF volumes.
PM2.5 exposure in the mid to high range (12.14–15.48 μg/m3) was associated with lower GM and higher CSF volumes (indicative of cerebral atrophy), while lower exposures (10.08 –12.14 μg/m3) were associated with higher GM volumes. Adjusting for urbanization removed these significant spline associations.
Gender was found to moderate the associations between air pollution and particulate matter/liquid levels, with stronger effects observed in men, especially for particulate matter.2.5P.M10and NO2. However, no significant interactions were found for T2DM status, age, LIBRA score, socio-economic position score or degree of urbanization.
The study is strengthened by the large population-based sample, middle-aged age range, detailed cognitive and MRI assessments, integration of air pollution data with individual risk factors for dementia, and stable regional environmental data for deeper analysis.
However, the study is limited by limited variation in exposure, possible misclassification of air pollution exposure, inability to account for long-term or indoor pollution, and possible selection bias toward healthier participants, reducing generalizability and limiting associations with Brain MRI and cognitive outcomes are diluted.
Conclusion
In conclusion, the study showed that there is moderate to high exposure to PM2.5 has been linked to increased CSF volumes, indicating reduced brain tissue volume or atrophy, but showed no association with cognitive functioning. Although these associations were observed, adjustment for urbanization weakened the findings.
Further research among diverse populations is needed to confirm these results, but reducing air pollution remains a potential target for public health policies aimed at protecting brain health.