The news over the past few weeks brought to light the increased risk of developing dementia from exposure to wildfire smoke. Air pollution has been identified as an increased risk factor for dementia for many years. It hasn’t been something that has grabbed the headlines but has now been thrust into widespread public awareness.
When I speak about brain health and the risk factors for developing dementia, I have focused more on the high levels of air pollution from traffic fumes or even burning wood in a fireplace. Air pollution is made of several different gases, chemical compounds, metals, and tiny particles known as particulate matter. The research has focused on a component of air pollution known as fine particulate matter.
Long-term exposure or exposure to high levels of air pollution can lead to health conditions that affect the heart and lungs. Now the research is looking for the link that implicates the connection between air pollution and dementia risk.
Research from the University of Michigan was published in JAMA Internal Medicine in August of 2023. Their study linked 18 years of data about people’s health to air pollution levels of each individual residential address. 28,000 people were in the study. None of them had a diagnosis of dementia at the start of the study. The average age was 61 years old and 57% were women. Among all of them, 15% developed dementia within an average period of 10 years, but those who lived in areas with high pollution levels were 8% more likely to develop dementia. The researchers examined dementia risk levels based on different types of pollution exposure, including exposure to agriculture, traffic, coal combustion, and wildfire pollution.
The widespread incidence of wildfires within North America is causing significant health risks for all populations. The increased risk of dementia is getting a lot of attention. The vulnerability of brain diseases from wildfires is a more recent discovery. Particulate matter from wildfires is so small that it can enter the brain directly through the nose or break through the brain-blood barrier in other ways. The findings are important because exposure to neurotoxic air pollution is considered ‘modifiable’ meaning that people’s exposure to pollution can be reduced or pollution itself can be reduced. “Our data suggest that in addition to some of the more obvious health impacts of wildfire smoke, like irritation to our throats and eyes along with breathing difficulties, high smoke days might also be taking a toll on our brains.” says researcher Sara Adar, ScD. “Our findings indicate that lowering levels of particulate matter air pollution, even in a relatively clean country like the United States, may reduce the number of people developing dementia in later life,” Adar said. (Air Pollution Linked to Higher Dementia Risk: Study, Aug. 15, 2023, webmd.com)
The Effect of Air Pollution on Dementia Risk
In 2022 the Committee on the Medical Effects of Air Pollutants undertook a review of 70 studies in human populations. The evidence suggests a link between air pollutants and the development of memory and thinking problems. It is thought that the effects of air pollution on the heart and circulatory system may impact the blood supply to the brain and lead to vascular dementia. (https://www.alzheimers.org.uk)
Air Pollution and the Brain
Magnetite, a form of iron, is released into the air by burning fuel and is found within fine particulate matter. A study of brain tissue from people in Mexico City and Manchester confirmed that magnetite from air pollution can pass into the brain, possibly via the bloodstream or the thin lining of the nose.
The particles were seen inside protein deposits called amyloid plaques, which are abundant in the brains of people with Alzheimer’s disease. This finding initially led to speculation that magnetite could be involved in the development of Alzheimer’s disease.
However, the study did not provide evidence that magnetite in involved in the formation of amyloid plaques or the death of brain cells. It could be that magnetite particles that enter the brain end up in amyloid plaques because of the brain waste disposal processes.
Research on Air Pollution and Thinking Skills
Studies involved in looking at people’s natural exposure to air pollution and thinking skills show that those exposed to high levels of pollutants perform poorer on thinking tests over time. But this does not mean they have or will develop dementia.
A study of 6.6 million people from Ontario, Canada found that those living within 50 meters of a major road were 7% more likely to develop dementia than those living more than 300 meters away. Another study in Quebec, Canada found an increase in dementia rates occurred with increased nitrous oxide or fine particulate matter exposure. They also saw an increase in relation to living closer to a major road.
I grew up living on a very busy road. To make matters worse, we lived by an intersection, and exhaust fumes were thick while people were sitting at the light. Also, my sales job had me on the road 80% of each day. Even then I worried about the impact of smelling car exhaust would have on me.
When I read these studies, I was very upset about how all of this might have put me at risk for dementia. It impressed me that living a brain-healthy lifestyle is even more critical for my brain health. These brain changes start early, long before we are aware that there might be a problem. Review your air pollution exposure history. Take this risk seriously. Fortunately, it is never too late to change your brain.
Alzheimer’s Society. Air pollution and the risk of dementia. Retrieved from https://www.alzheimers.org.uk/about-dementia/managing-the-risk-of-dementia/reduce-your-risk-of-dementia/air-pollution
O’Mary, L. (August 15, 2023). Air pollution linked to higher dementia risk: study. Retrieved from https://www.webmd.com/alzheimers/news/20230815/air-polution-linked-elevated-dementia-risk-study
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