Air pollution can contribute to the risk of Alzheimer’s disease and dementia

(Conversation) Alzheimer’s disease is the most common cause of dementia. It slowly destroys memory, thoughts, actions, and ultimately the ability to perform everyday tasks.

When scientists are looking for a cure, we are learning more about the genetic and environmental factors that can increase the risk of people developing dementia associated with late-onset Alzheimer’s disease. ..

In particular, my colleagues in preventive medicine, neurology, and gerontology and I are focusing on the role of outdoor air pollution.

Our early study in 2017 used both human and animal data in the United States to show that air pollution-induced brain aging processes can increase the risk of dementia. This was my first study. Our latest study shows that older women (particulate matter produced by vehicles and power plants) who lived in high PM2.5 levels do not have the memory of women living in cleaner air. It shows how they suffered from loss and brain contractions such as Alzheimer’s disease.

Taken together, these findings suggest ways to avoid one risk factor for Alzheimer’s disease: reduce human exposure to PM2.5. Unfortunately, it’s not as easy as it sounds.

Silent risk of dementia

PM2.5, also known as soot, consists of fine particles of chemicals, automobile exhaust, smoke, dust, and other pollutants floating in the air. An estimated 1 in 6 Americans live in counties with unhealthy levels of particle contamination.

We are investigating whether PM2.5 may accelerate the aging process of the brain in the preclinical stage (the “silent” stage of the disease before the onset of symptoms of Alzheimer’s disease and associated dementia). I will.

The first US-based national study linking PM2.5 exposure to cognitive impairment, published in 2017, found that older women clinically lived outdoors above PM2.5 levels. It turns out that the chances of developing serious cognitive impairment are almost doubled, and the US Environmental Protection Agency’s standards are better than they would otherwise be. Collaborating with a memory study of the Women’s Health Initiative, which closely followed participants, was able to explain other risk factors for dementia such as smoking, lack of exercise, and hormone therapy.

In a new study, I wanted to see how the brains of older people change when they experience different levels of PM2.5 in the years before the onset of symptoms of Alzheimer’s disease.

We followed the progression of 712 women with an average age of 78 years who had no dementia at the start of the study and underwent MRI brain scans at 5-year intervals. By combining EPA monitoring data with air quality simulations, we were able to estimate daily outdoor PM2.5 levels around where participants lived prior to their first MRI scan.

Older women were found to be more likely to have brain contractions similar to those observed in patients with Alzheimer’s disease. Comparing brain scans of older women from high levels of PM2.5 with low levels of PM2.5, we found that the risk of dementia increased by 24% over a five-year period.

Perhaps even more alarming is that these Alzheimer’s-like brain changes were seen in older women with no memory problems. Their brain contractions were greater when living in areas with high levels of outdoor PM2.5, even if their levels were within current EPA standards.

Spanish researchers recently examined brain MRI scans of healthy individuals at risk for Alzheimer’s disease and reduced air pollution exposure and volume and thickness in certain brain regions known to be affected by Alzheimer’s disease. I also found a connection with.

Pollution and brain contraction

We also focused on episodic memory, which includes memories of specific events and is affected early in Alzheimer’s disease. If episodic memory decline is associated with living in a location with increased PM2.5, see evidence that such particular cognitive decline resulted from brain contractions such as Alzheimer’s disease. Can you?

The Women’s Health Initiative Memory Study and past MRI data were able to look for changes over time in nearly 1,000 women. It was found that episodic memory decreased as outdoor PM2.5 increased where these older women lived. About 10% to 20% of major memory loss can be explained by brain contractions such as Alzheimer’s disease.

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Since the silent period of dementia is thought to begin decades before symptoms appear, recent studies have shown that exposure to middle-aged to early air pollution is equal to or greater than that of later years. It can be important.

Genes also seem to play a role. Our study shows that APOE4, an important risk gene for Alzheimer’s disease, interacts with air particles to accelerate brain aging. We found that the environmental risks posed by long-term PM2.5 exposure were 2-3 times higher in older women with two copies of the APOE4 gene than in women without the gene.

Later, other researchers investigated the potential interaction between the gene and the environment. A 2019 Swedish study found no strong evidence of gene-environment interactions. However, a 2020 study using data collected from older people in two New York City neighborhoods found a link between long-term air pollution exposure and cognitive decline, which was sharp for APOE4 carriers. A rate of decline was seen.

Avoidable risks

In the United States, the Clean Air Act requires the Environmental Protection Agency to develop air quality standards that provide sufficient safety margins to protect sensitive people such as children and the elderly.

The US government had the opportunity to tighten these standards in 2020. This is a move described by EPA scientists to prevent the premature death of thousands of people due to health risks such as heart disease. Scientists have proposed stricter standards, citing other health issues related to PM2.5. However, EPA administrator Andrew Wheeler declined and announced on December 7 that the standards would remain unchanged.

This article has been republished from Conversation under a Creative Commons license. Read the original article here: https://theconversation.com/air-pollution-may-contribute-to-alzheimers-and-dementia-risk-heres-what-were-learning-from-brain-scans-148776..