The impact of air pollution on neurodegenerative diseases: a growing public health concern

The link between air pollution and neurodegenerative diseases

How does air pollution affect brain health in general?

Recent studies have established a compelling connection between long-term exposure to air pollutants and an increased risk of developing neurodegenerative diseases. Fine particulate matter (PM2.5), nitrogen dioxide (NO₂), and other pollutants have been identified as significant contributors to cognitive decline and neurodegeneration. For instance, a study analyzing health records of 1.2 million older adults in Southern California found that each 1 microgram increase in wildfire-related PM2.5 exposure was associated with a 21% higher risk of dementia diagnosis, compared to a 3% increase for every 3 microgram rise in non-wildfire particles.

The pathophysiological mechanisms through which air pollution affects brain health are multifaceted. Exposure to air pollutants can lead to systemic inflammation, oxidative stress, and disruption of the blood-brain barrier (BBB), facilitating the entry of toxic substances into the brain. These processes can result in neuronal damage, accumulation of amyloid plaques and tau tangles, and activation of microglia—the brain’s resident immune cells—which contribute to neuroinflammation and neurodegeneration.

Focus on Lewy Body Dementia (LBD)

A recent study conducted by Johns Hopkins University has highlighted a significant link between long-term exposure to fine particulate air pollution (PM2.5) and the onset of Lewy body dementia. The study analyzed Medicare records of 56.5 million U.S. beneficiaries between 2000 and 2014, revealing a strong correlation between PM2.5 exposure and an increased risk of developing LBD.

Lewy bodies are abnormal clumps of the protein alpha-synuclein, which disrupt neuronal function and ultimately lead to cell death. Researchers found that PM2.5 exposure promotes the misfolding of alpha-synuclein into a toxic, aggregation-prone form known as PM-PFF (PM2.5-induced preformed fibril), which is particularly resistant to cellular degradation and more neurotoxic than spontaneously formed aggregates.

Animal experiments demonstrated that mice exposed to PM2.5 for 10 months exhibited brain atrophy, neuronal loss, and cognitive decline that are hallmarks of LBD. Notably, these effects were absent in genetically modified mice that do not produce alpha-synuclein, highlighting the central role of this protein in pollution-induced pathology.

The study suggests that air pollution, especially PM2.5, may accelerate the development of Lewy body dementia in genetically predisposed individuals, rather than directly causing the disease.

Evidence of an impact on other neurodegenerative diseases

Alzheimer’s Disease (AD) and Parkinson’s Disease (PD) are also influenced by air pollution: studies have shown that exposure to air pollution accelerates the accumulation of amyloid and tau proteins in the brains of Alzheimer’s patients, leading to faster cognitive decline. In the same way, research indicates that long-term exposure to air pollutants increases the risk of developing Parkinson’s disease. The neurotoxic effects of pollutants may exacerbate the degeneration of dopaminergic neurons characteristic of PD.

The importance of prevention

Certain populations are more susceptible to the adverse effects of air pollution on brain health. Older adults, individuals with pre-existing health conditions, and those living in areas with high pollution levels are at increased risk. Additionally, socioeconomic factors may influence exposure levels and access to healthcare, further exacerbating health disparities.

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The association between air pollution and neurodegenerative diseases underscores the need for comprehensive public health strategies to reduce particulate emissions, such as managing wildfires, limiting domestic wood burning, and curbing industrial and vehicular pollution, to protect brain health and prevent certain neurodegenerative diseases.

Furthermore, public awareness campaigns can educate communities about the risks of air pollution and encourage protective measures, such as reducing outdoor activities during high pollution periods. This has been done for example in the United States with AirNow, a website and app from the U.S. Environmental Protection Agency, providing real-time air quality indices for cities nationwide, as well as in Sweden. Studies have suggested that these air quality warnings improve risk perception and prompt behavioural adjustments such as limiting outdoor activity or postponing exercise.

The growing body of evidence linking air pollution to neurodegenerative diseases highlights the importance of addressing environmental factors in public health initiatives. By understanding the mechanisms through which pollutants affect brain health and implementing effective policies to reduce exposure, it is possible to mitigate the impact of these diseases on individuals and society. Continued research is essential to further elucidate the complex relationship between air pollution and neurodegeneration, ultimately leading to improved prevention and treatment strategies. Our specialized healthcare team will follow the developments closely! Don’t hesitate to contact our team.

About the author, 

Diane, Project Manager in Alcimed’s Healthcare team in Germany