Link Between Air Pollution And Dementia

This article provides an overview of the study conducted to determine if there is a link between airborne particulate matter exposure and pathological brain aging in older women. Older women staying in different regions and not having neurodegenerative disorders were included in the study. The researchers followed the same experimental set up in the mouse models.

Particulate matter (ambient fine particles) with diameter < 2.5µm from traffic emission are a major source of urban pollution, accounting globally for 25% ambient PM.  Epidemiologic studies indicate the association between cognitive deficits with PM exposure in elderly.

Rodent models also indicate long-term neurotoxic effects of air pollutants including memory impairment and selective atrophy, decreased glutamate receptor subunit GluR1, and increased endogenous soluble Aβ. This study was designed to determine if there is a link between PM exposure and Alzheimer’s disease (AD) and related dementias (ADRD) risk.

Study Subjects: A study was conducted on 3647 elderly women, with age between 65 to 79. The women were selected from different regions. Also, the researchers have included the mice model for comparison.

Study Highlights:

  1. Elderly women residing in the areas where the air pollution exceeded the standard levels, were twice as likely to develop dementia, including Alzheimer’s disease (AD).
  2. The study also indicated the women who already had a high genetic predisposition for Alzheimer’s had almost 263% increased risk for the disease.
  3. In animal experiments, mice were exposed to controlled amounts of particulate matter air pollution for 15 weeks. These mice were 60% more likely to have amyloid plaques associated with AD compared to mice not exposed to the pollution.
  4. Fine-particle pollution is a toxic stew of soot, chemical compounds, and other airborne specks no bigger than 2.5 microns in diameter are about 1/28th the width of a human hair.
  5. People living near freeways, ports, and warehouses are exposed to higher amounts because of the diesel exhaust.
  6. The joint data from humans and mice provide the first evidence that the neurodegenerative effect of pollution may involve gene-environment interactions with APOEε4, the major genetic risk factor for pathological brain aging and AD.
  7. A previous research also found that these pollution particles are so tiny that they can move from the blood stream through cell walls and go into our brains. There the particles trigger the immune system response resulting in the formation of plaques associated with neuro-degenerative diseases.

In summary, the study establishes a link between exposure of particulate matter (<2.5µm) and increased risk of dementia. However, the study has a global implication because the pollution knows no border. And thus, more studies in different regions of the world are necessary.

Reference: Cacciottolo, M., et al. “Particulate air pollutants, APOE alleles and their contributions to cognitive impairment in older women and to amyloidogenesis in experimental models.” Translational Psychiatry 7.1 (2017): e1022.


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