The Role PM2.5 Plays in Cognitive Decline and Incident Dementia

A woman holding her husband, with dementia, shoulders. Dementia has been linked with air pollution and pm2.5.
“Both increasing levels of air pollution and increasing cases of dementia are worldwide public health crises.”

Dementia, which is a broad umbrella term for several diseases that affect cognitive function, is the seventh leading cause of death globally and is estimated to affect over 57 million people worldwide, with 10 million new cases each year.

PM2.5 and Health Risks

Risk factors of developing dementia include older age, health and behavior, hearing loss, social isolation, genetics, and environmental aspects. Of the 57 million cases worldwide, it is estimated that up to 40% are thought to be linked to “potentially modifiable risk factors” – including air pollution, more specifically fine particulate matter. Studies suggest that exposure to PM2.5 is harmful in large amounts, and chronic, long-term exposure to PM2.5 results in Alzheimer's Disease-like cognitive impairment.

Not only does PM2.5 correlate with cognitive impairment, but it has also been linked to “heart disease, lung cancer, and emphysema.” Inhalation of particulate matter is associated with “increased onset and mortality of diseases involving the pulmonary, cardiovascular, immune, and central nervous system.” PM2.5 uses the olfactory system, the nose and mouth, to traverse the body, allowing it to reach the lungs and even the bloodstream. Once PM2.5 reaches the bloodstream, which delivers oxygen to the brain, the pollutant is able to change gene expression and cause neuronal cell death of white matter, which affects learning and communication of the central nervous system.

Air Pollution and Incident Dementia

A study from JAMA Internal Medicine was conducted over a 10-year period with close to 28,000 participants. This study collected survey data (including the subject’s cognition, health, and health behaviors every two years), air quality data (from the EPA), and information on contributing factors (including nearby transit and population density) gathered to determine the effect of PM2.5 on individuals and their cognitive health.

The study found that “higher concentrations of PM2.5 were associated with greater rates of incident dementia.” Of the almost 28,000 participants, 15% developed dementia in the 10-year study period. When assessing which sources of PM2.5 are likely most responsible for the increased risk of developing dementia, researchers found that “PM2.5 from agriculture and wildfires were robustly associated with greater rates of dementia.”

Similarly, a Harvard study found “exposure to fine particulate air pollutants (PM2.5) may increase the risk of developing dementia.” Researchers also found a “17% increase in risk for developing dementia for every 2 μg/m3 increase in average annual exposure to PM2.5” – independent of socio-demographics and health behaviors. These two studies, as well as 51 others identified by Harvard researchers, discovered and evaluated an association between air pollution and dementia, which led them to identify the main issue – exposure to mass amounts of dangerous particulate matter.

Facing the Issue Head On

"Many other factors that impact dementia are not changeable, but reductions in exposure to air pollution may be associated with a lower risk of dementia.”

While there isn’t a definitive “cure” for dementia and cognitive decline, there are steps that can be taken to reduce the harm and progression of onset cognitive dysfunction. Preventative measures to reduce the impact of particulate matter include the implementation of policies that aim to reduce PM2.5 levels, as well as tighter limits and standards on air pollution. Improving air quality may reduce the risk of cognitive decline and decrease the lifelong risk of developing dementia. Improved air quality is also suggested to have “a positive impact on multiple underlying regions of the brain,” as well as critical body systems.

The challenging part of implementing preventative measures on an individual basis is that there are many sources that continue to pollute the air, despite efforts by agencies and government bodies to reduce and restrict pollution production. This has led to the search for and creation of new, resourceful methods of cleaning the air we breathe. Without stricter governmental regulations on pollutant sources, it is crucial that we find a way to purify the air of contaminants that can cause harm to bodily functions, especially indoors where we have much greater control over air quality.

The link between chronic exposure and cognitive decline is hard to ignore. While scientists might not fully understand why or how particulate matter affects the brain and causes said decline in cognition, they recognize the urgency of this developing global issue as poor air quality caused by pollution becomes strikingly more common. An increase in efforts to reduce air pollution and improve air quality can help diminish the impact of particulate matter. It is not only important to improve the quality of the air outside but inside too - as concentrations of pollutants inside are often exponentially higher compared to outdoor air. By installing an ActivePure air purifier paired with a HEPA filter, you can address a wide range of pathogens, harmful VOC gases, and unhealthy contaminants including wildfire smoke particulates. Learn more about the harms of particulate matter and air pollution below.

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