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Air Pollution Tied to a Higher Risk of Dementia

By Emily Withnall | September 18th, 2018

Air pollution is on the rise, and there’s no question that it’s bad for your respiratory system. Scientists have linked pollution to around 9 million premature deaths and officially classified it as a human carcinogen and a leading environmental cause for cancer deaths. But could air pollution affect the brain, too?  

A new study suggests a possible link between air pollution and dementia—by up to as much as a 40 percent increased risk. As part of the London Traffic Project, researchers analyzed 131,000 anonymous patient records for patients ages 50 to 79. These patients had received care at 75 different health clinics located within the radius of a major highway. Researchers collected data from records of patients with no dementia diagnosis and tracked their health history for approximately seven years, beginning in 2004.

By measuring air pollutants in the areas where patients lived, researchers were able to estimate how much pollution patients were exposed to each year. They measured the levels of nitrogen dioxide (NO2), a type of molecule produced by industrial activity; fine particulate matter (PM2.5), which shows up as dust and soot caused by burning fossil fuels; and ozone (O3), a byproduct of pollution reacting with sunlight.

While the study was in progress, 2,181 patients, or 1.7 percent of the study’s population, were diagnosed with dementia, including Alzheimer’s. Patients who lived in areas with the highest levels of NO2 were found to be 40 percent more likely to receive a dementia diagnosis than patients living in areas with the lowest levels. The findings yielded similar results for patients living in areas with high levels of PM2.5 compared with patients living in areas with low levels of PM2.5.

Although there are studies that show the correlation between smoking and dementia, and diabetes and dementia, researchers for the London study accounted for these potential factors and reported that the correlation between poor air quality and dementia remained, regardless of whether patients had a history of smoking or diabetes. Perhaps most surprisingly, when researchers attempted to correlate air pollution levels with specific kinds of dementia, the correlation only remained for Alzheimer’s. This may suggest a link between air pollution and higher incidence of Alzheimer’s.  

Since observational studies cannot control for other variables such as unknown lifestyle or environmental factors that might have contributed to the higher rate of dementia, more research is required to determine whether air pollution is one cause for dementia diagnoses. Alzheimer’s can take many years to develop and a seven-year study doesn’t cover the effects of long-term air pollution on dementia diagnoses. And experts who were not involved in the study said it’s not cause for alarm.

“Air pollution is a hot topic in dementia research, and there is evidence that exposure to air pollution can cause small particles to enter the brain, but it’s a huge leap to say that air pollution could lead to dementia and this study had several limitations,” said James Pickett, Head of Research at Alzheimer’s Society.

However, other studies on air pollution and brain health appear to support the findings of this latest study. One study from the University of Montana aggregated the results from autopsies from people living in Mexico City and discovered a correlation between exposure to pollution and signs of dementia. In another study conducted in China, researchers have found that air pollution may significantly decrease intelligence. The study reports that the most significant decrease in intelligence is found in people over the age of 64.

Although more research needs to be done to confirm these studies’ findings, the results all suggest that making efforts to reduce air pollution would be in everyone’s best interest. As the researchers of the BMJ Open study report, “Traffic-related air pollution has been linked to poorer cognitive development in young children, and continued significant exposure may produce neuroinflammation and altered brain innate immune responses in early adulthood.”

Exposure to air pollution at a young age can negatively impact brain health. These effects only increase with prolonged exposure to air pollution. If you live in a polluted area, study authors said the best way to lower your risk is to avoid exposure—and that starts with knowing where most pollution occurs.

For example, in cities, apps like CityAir can be used to plan journeys that minimize exposure, or you can try and travel outside rush hours,” said study author Frank Kelly. “Indoors, you can minimize pollution by not burning candles, open fires and having good ventilation/extraction when cooking and cleaning. Face masks do not usually work unless they are an extremely good fit to the face and have good filters in place—i.e., the most expensive.”

Minimizing exposure to air pollution can be challenging, particularly if you live in a large urban area. Air filters can also help reduce the quantity of pollutants in the air. If you have access to them, green spaces provide a natural air filtering system in addition to increasing the possibility of exercise and enhancing your mood.

 

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