Traffic-related air pollution linked to increased Alzheimer's risk

Our cities are full of life, bustling with traffic and daily activities. But hidden in the air is a danger we can’t see: tiny particles called PM2.5, mostly from car exhaust. 

We know air pollution hurts our lungs and hearts, but new research from Emory University suggests something even scarier: it might raise the risk of Alzheimer’s disease, a brain illness affecting millions of people.

Brain tissue markers

This study looked at the possible link between air pollution and brain changes related to Alzheimer’s disease. The researchers examined brain tissue from 224 individuals with confirmed Alzheimer’s disease who had donated their brains after passing away.

They checked for signs of Alzheimer’s disease by looking for specific markers in the brain tissue, like neuritic plaques. This helped them assess the severity of the disease.

Air pollution exposure

The experts estimated how much air pollution people were exposed to based on where they lived and traffic patterns. Different timeframes (1 year, 3 years, 5 years) were considered before the person passed away.

The researchers used statistical models to see if there was a connection between air pollution exposure and the severity of Alzheimer’s disease markers. They also considered whether a specific gene, Apolipoprotein E (APOE), influenced this connection.

Increase in neuritic plaques

The researchers found that higher exposure to PM2.5 was associated with higher levels of neuritic plaques in the brain. These are protein clumps considered a hallmark of Alzheimer’s disease.

The more PM2.5 someone was exposed to, the higher their risk of having more plaques. People with higher PM2.5 exposure were nearly twice as likely to have higher plaque levels compared to those with lower exposure.

The link was stronger when looking at PM2.5 exposure in the year before death. This suggests a potentially shorter-term impact of air pollution on Alzheimer’s brain changes. 

“These results add to the evidence that fine particulate matter from traffic-related air pollution affects the amount of amyloid plaque in the brain,” said study author Anke Huels from Emory University in Atlanta. “More research is needed to investigate the mechanisms behind this link.”

Genetic influence 

The team explored whether the link between air pollution and Alzheimer’s brain changes were influenced by genetics. The study was specifically focused on the APOE gene, which is known to increase Alzheimer’s risk.

The analysis revealed that people without the APOE gene seemed more affected by air pollution in terms of Alzheimer’s brain changes. 

For those without the gene, higher air pollution exposure was linked to a more than two-fold higher risk of having more plaques.

“This suggests that environmental factors such as air pollution could be a contributing factor to Alzheimer’s in patients in which the disease cannot be explained by genetics,” Dr Huels said.

Environmental factors

The study shows that things in our environment, like air pollution, can affect our chances of getting Alzheimer’s disease. This means we can potentially prevent Alzheimer’s by paying attention to the environment and keeping it healthy.

Air pollution has been linked to changes in the brain that are similar to those seen in Alzheimer’s. This suggests that stricter rules are needed to limit air pollution, especially PM2.5, which comes from car exhaust and other sources. Lowering these limits in cities and factories could help protect people’s health.

The study also suggests that cities could be designed differently to reduce air pollution from traffic. This could involve making it easier and safer for people to walk, bike, or use public transportation, instead of driving cars.

Global health implications

People with lower incomes and those living in certain areas are often exposed to more air pollution. The findings suggest that reducing these differences in how much pollution people are exposed to could be important for preventing Alzheimer’s disease.

Air pollution is a major threat to public health around the world, and so is Alzheimer’s disease. This means that the findings are important for everyone. By cleaning up the air we breathe, we could help prevent Alzheimer’s disease in many different communities around the world.

The study is published in the journal Neurology.

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