Air Pollution As a Cause of Dementia
Dementia is a devastating condition with multiple risk factors that can contribute to its development. While age is the most obvious risk factor, diet, exercise, smoking, blood sugar problems and infections all appear to play a role (Chen 2009, Kandimalla 2017). Recent research has also begun to unearth another risk factor that appears relevant: air pollution.
Air Pollution and Dementia
Data on air pollution and its relationship to dementia risk has been growing. In 2017, the Lancet Commission on Pollution and Health officially added air pollution as a potential risk factor for dementia (Landrigan 2018).
A study out of Sweden compared dementia incidence with exposure to traffic pollution based on the subject’s home address. The study found that traffic pollution alone increased the risk for dementia by 43% (Oudin 2016).
A similar study from Ontario, Canada, found that living close to a busier road was associated with a smaller but still significant 7% increased risk of developing dementia (Chen 2017). In England, results suggest a 40% increased risk of dementia for those living in areas with higher levels of traffic-related pollution (Carey 2018). In the United States, a study found that exposure to air pollution, predominantly considered to be from traffic, could increase the risks for dementia by upwards of 20% in those with the highest levels of exposure (Shi 2023).
Further research suggests that the risks may be greatest in older adults with other risk factors. A study Of Mexican Americans in California found the highest risk for dementia from air pollution coincided with higher blood sugar levels and lower high density lipoprotein, or “good” cholesterol levels (Yu 2020). As such, it is likely possible to protect from the risks of air pollution through strategies that support lower blood sugar and healthier cholesterol.
Overall Dementia Risk from Air Pollution
A meta-analysis of studies on air pollution and dementia found a significant correlation (Wilker 2023). For particles under 2.5 micrometers in size, often referred to as PM2.5, there was a 4% increased risk for every two micrograms per cubic meter increase. To put this into context, during recent forest fires, some parts of the East Coast in the United States had PM2.5 levels that exceeded 400. If air pollution levels stayed that high continuously, the risk for dementia would increase by 800% for exposed individuals.
Air pollution affects the brain in a number of ways. First, small PM2.5 particles can penetrate deep into the lungs and enter the bloodstream. Once in the bloodstream, they damage blood vessels leading to plaque buildup in arteries, elevated blood pressure and blood sugar problems (Münzel 2018). These problems can compromise blood flow to the brain and damage the blood brain barrier, which normally provides protection.
Data from animal and human studies also appears to confirm that air pollution exposure increases tau tangles inside brain cells (Serafin 2023). These tangles are clumps of excess protein that disrupt normal cellular function and are believed to contribute to the development of dementia. Air pollution has also been shown to correlate with higher levels of amyloid plaque development in the brain (Alemany 2021).
Reducing the Risks
While the relationship between air pollution and dementia risk has only recently been established, there aren’t many studies exploring ways to mitigate the risks. However, it’s likely that several approaches may be helpful.
First, if you have a choice, don’t live near large sources of air pollution. In some cases, this may be easier said than done. For situations where this isn’t possible, decreasing air pollution inside the living space will likely help. HEPA-quality air filters can reduce air pollution inside a home. While separate air filters can be purchased, in some situations, using a HEPA-rated filter installed in the existing heating, ventilation and air conditioning (HVAC) system can be effective. To get the most out of a home’s HVAC filtration, the fan needs to be run continuously so the filter is constantly working to clean the air. Filters also need to be replaced according to manufacturer’s recommendations to provide optimum benefits.
Paying attention to the air quality index can also help to mitigate exposure. The air quality index is a measurement describing current levels of air pollution. Air pollution levels are variable based on numerous factors and can be tracked online through websites that monitor levels. When air pollution is high, minimizing outdoor activities can decrease exposure. If levels are really high, a mask that is certified to filter particulates from the air, like an N95 mask, can also reduce exposure risks (Bissiri 2022).
Air pollution appears to significantly increase the risks for dementia. Being aware of the risks and working to reduce exposures may help to decrease the risks for developing cognitive decline and dementia.