Air Pollution’s Effect on Dementia
As the number of dementia cases continue to increase, researchers have been attempting to find the causes behind this currently incurable disease. Recent studies have found a link between air pollution and brain function as well as a connection between air pollution and cardiovascular health. A group of researchers from Sweden have taken a closer look to test their hypothesis, which states that exposure to air pollution is associated with higher rates of dementia, and increased cardiovascular disease strengthens that link.
The researchers used data from the 2001-2013 Swedish National Study on Aging and Care in Kungsholmen, an urban city in Sweden, which randomly chose individuals who were 60 years of age or older and examined them for a 12-year period. In collecting data to test their hypothesis, researchers selected eligible individuals from the national study and followed up with them. Dementia diagnoses were carried out for each individual through a multi-step procedure that required at least two physicians to agree on a diagnosis. Dementia was specified into two categories: Alzheimer’s Disease and vascular dementia, a type of dementia caused by restricted blood flow to the brain. Assessments of air pollution in the city for the past 11 years were compiled using local emission inventories and specifically focused on NOx (nitric oxide and nitric dioxide) levels and PM2.5 (particulate matter less than 2.5 micrometers in diameter) levels, as both of these substances are common air pollutants. Potential confounding factors, other variables that may affect the onset of dementia, were taken into account, as well.
The researchers used data from the 2001-2013 Swedish National Study on Aging and Care in Kungsholmen, an urban city in Sweden, which randomly chose individuals who were 60 years of age or older and examined them for a 12-year period. In collecting data to test their hypothesis, researchers selected eligible individuals from the national study and followed up with them. Dementia diagnoses were carried out for each individual through a multi-step procedure that required at least two physicians to agree on a diagnosis. Dementia was specified into two categories: Alzheimer’s Disease and vascular dementia, a type of dementia caused by restricted blood flow to the brain. Assessments of air pollution in the city for the past 11 years were compiled using local emission inventories and specifically focused on NOx (nitric oxide and nitric dioxide) levels and PM2.5 (particulate matter less than 2.5 micrometers in diameter) levels, as both of these substances are common air pollutants. Potential confounding factors, other variables that may affect the onset of dementia, were taken into account, as well.
Image Source: SD-Pictures
The study found a high correlation between dementia and exposure to air pollutants. More specifically, vascular dementia had a significant link to PM2.5 and NOX levels, while Alzheimer’s Disease did not. There was also an overall increased risk of dementia associated with exposure to PM2.5 and NOX in people with heart failure and ischemic heart diseases. Higher levels of PM2.5 led to a 75% increased chance of dementia, while higher NOX led to a 66% increased chance of dementia. Overall, researchers concluded that the last five years of air pollutant exposure is crucial when determining the risk of dementia. Furthermore, cardiovascular diseases strengthened the correlation between air pollution and dementia.
The researchers also provided possible explanations for this connection. First, particulate matter can reach the brain through blood circulation, damaging the brain and inducing inflammation. Particulate matter can also affect the brain indirectly; air pollution has been proven to negatively impact cardiovascular health, which in turn has shown to be associated with cognitive decline and onsets of dementia. These suggestions are further strengthened by the finding that while Alzheimer’s was not associated with higher levels of pollution, vascular dementia was.
The results of this study are especially important from the perspective of public health. This is not the only study to have found a relationship between air pollution and dementia and even between air pollution and cardiovascular diseases; studies done in the United States; Ontario, Canada; and other cities in Sweden all showed similar findings. Most concerning is the fact that the highest level of air pollution found to increase risk of dementia is still lower than the particulate matter limits imposed by law both in Europe and in the US. Thus, current regulation is not enough to protect people’s health from air pollution. This is especially concerning because most individuals who live in heavily polluted areas are of lower socioeconomic classes or minorities. Consequently, these findings prove an increasing need for stricter environmental regulations for a healthier and safer environment for all.
The researchers also provided possible explanations for this connection. First, particulate matter can reach the brain through blood circulation, damaging the brain and inducing inflammation. Particulate matter can also affect the brain indirectly; air pollution has been proven to negatively impact cardiovascular health, which in turn has shown to be associated with cognitive decline and onsets of dementia. These suggestions are further strengthened by the finding that while Alzheimer’s was not associated with higher levels of pollution, vascular dementia was.
The results of this study are especially important from the perspective of public health. This is not the only study to have found a relationship between air pollution and dementia and even between air pollution and cardiovascular diseases; studies done in the United States; Ontario, Canada; and other cities in Sweden all showed similar findings. Most concerning is the fact that the highest level of air pollution found to increase risk of dementia is still lower than the particulate matter limits imposed by law both in Europe and in the US. Thus, current regulation is not enough to protect people’s health from air pollution. This is especially concerning because most individuals who live in heavily polluted areas are of lower socioeconomic classes or minorities. Consequently, these findings prove an increasing need for stricter environmental regulations for a healthier and safer environment for all.
Featured Image Source: geralt
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