Air Pollution Linked to Increased Alzheimer’s Markers in the Brain

Air Pollution Linked to Increased Alzheimer's

A recent study found that amyloid plaques, the biomarkers for Alzheimer’s, were more prevalent in the brains of those exposed to higher concentrations of fine particulate air pollution. The researchers found the highest association between pollution exposure and plaques among people who did not have a gene variant that increases the risk of Alzheimer’s.

According to a recent study published in Neurology, people with higher exposure to traffic-related air pollution were also more likely to have high amyloid plaque levels in their brains related to Alzheimer’s after death [1].

Anke Huels, assistant professor at Emory University in Atlanta and one of the study authors, stated that these findings strengthen the evidence that fine particulate matter from traffic-related air pollution influences the quantity of amyloid plaque in the brain.

The results also contribute to an expanding body of research demonstrating the various effects air pollution can have on health in general. For instance, Huels and her team have already investigated the impact of small particle pollution on skin aging and respiratory health [2].

Association of Air Pollution and Alzheimer’s

In a recent study, Huels and her team investigated brain tissue from 224 deceased individuals whose average age was 76.

According to research, those with higher exposure levels to fine-particulate air pollution, known as airborne particulates with a diameter of less than 2.5 microns, had an increased risk of having high levels of amyloid plaque in their brains.

The researchers investigated traffic-related air pollution exposure based on the individuals’ home addresses in the Atlanta region at the time of death. In metropolitan locations such as the metro Atlanta area (where the majority of donors lived), traffic-related PM2.5 levels are a substantial source of air pollution. In the year before death, the mean exposure level was 1.32 micrograms per cubic meter (µg/m3), and in the three years preceding death, it was 1.35 µg/m3.

Next, they examined the relationship between exposure to pollution and two indicators of Alzheimer’s disease in the brain: tau tangles and amyloid plaques. They discovered individuals with more exposure to air pollution one to three years before dying had higher amounts of amyloid plaques in their brains.

Those who exposed themselves to 1 µg/m3 more PM2.5 in the year preceding their death were almost twice as likely to have plaques, and those who exposed themselves to more PM2.5 in the three years before death were 87% more inclined to have plaques.

Heuls stated that one biological mechanism involving small particles is that they can penetrate the blood-brain barrier and reach the brain when inhaled. These particles are hazardous and, therefore, can cause damage as soon as they enter the brain.

How Genetics Contribute to Alzheimer’s Risk

Researchers also examined the potential impact of APOE e4, the primary gene variant linked to Alzheimer’s, on the association between Alzheimer’s signs and air pollution. According to the findings, the individuals without the gene variant showed the highest correlation between air pollution and the disease symptoms.

Huels stated that their findings implied that in patients for whom genetics cannot account for the condition, environmental factors like air pollution may have a role in the development of Alzheimer’s.

What are the Limitations of this Study?

One limitation of the study is that the research team only obtained people’s home addresses at the time of death to measure air pollution, suggesting possible misclassification of the pollution exposure. Furthermore, the majority of the highly educated white participants in the study may not be indicative of other communities.

Huels suggested that follow-up studies could attempt to reproduce the findings in larger brain banks.

References

  1. Christensen, G.M., Li, Z., Liang, D., Ebelt, S., Gearing, M., Levey, A.I., Lah, J.J., Wingo, A., Wingo, T. and Hüls, A., 2024. Association of PM2. 5 Exposure and Alzheimer Disease Pathology in Brain Bank Donors—Effect Modification by APOE Genotype. Neurology, 102(5), p.e209162.
  2. Ding, A., Yang, Y., Zhao, Z., Hüls, A., Vierkötter, A., Yuan, Z., Cai, J., Zhang, J., Gao, W., Li, J. and Zhang, M., 2017. Indoor PM2. 5 exposure affects skin aging manifestation in a Chinese population. Scientific reports, 7(1), p.15329.
  3. Why Alzheimer’s risk may be higher for people exposed to air pollution. Medical News Today. https://www.medicalnewstoday.com/articles/why-alzheimers-risk-may-be-higher-for-people-exposed-to-air-pollution. Published Online: 21st February, 2024. Accessed: 7th March, 2024.
  4. Study links air pollution with increased Alzheimer’s markers. News Medical. https://www.news-medical.net/news/20240221/Study-links-air-pollution-with-increased-Alzheimers-markers.aspx. Published Online: 21st February, 2024. Accessed: 7th March, 2024.
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