Scientists have been looking for the many causes of dementia. These studies have produced curious findings. In fact, a new study that involved rodents found a link between traffic-related air pollution and a higher risk of age-related dementia.
In the study that was conducted, the researchers found that exposure to traffic-related air pollution accelerated the Alzheimer’s disease characteristics in animals who had the risk gene and also in wild-type rats. Hence, they concluded that traffic-related air pollution might decrease the time to Alzheimer’s onset and accelerate the progression of dementia.
The Studies Made
A growing number of studies have been made by researchers and many of the findings suggest how air pollution could be associated with a higher risk of developing dementia or Alzheimer’s disease.
The World Health Organization (WHO) conducted a study and statistics in the reports made show that around 50 million people globally suffer from dementia. Alzheimer’s disease, on the other hand, is an irreversible and progressive neurological condition that causes memory loss and cognitive decline to those who suffer from it. The latter is the most common form of dementia as it accounts for an estimated 60 to 80 percent of the reported cases.
A new study conducted by the researchers at the University of California, Davis adds to the body of research that suggests the possible link between traffic-related air pollution and an increased risk of developing age-related dementia, included of which is Alzheimer’s disease.
The study that was recently conducted has appeared in the journal Environmental Health Perspectives. The said journal is a must-read for doctors and health experts who tackle the field of dementia. The researchers behind it had set up a rodent vivarium that was located close to a well-used traffic tunnel found in Northern California. They used the aforementioned setup in order to replicate the pollution that the people from all over encounter and are exposed to while they’re stuck in traffic with cars that emit dangerous exhaust fumes.
Behind this insightful research is senior study author Dr. Pamela Lein. She is a professor of neurotoxicology at the University of California in Davis. She had recently spoken to the writers of Medical News Today about the main difference between this research and the others that had previously been conducted and said, “Because epidemiologic studies can provide evidence regarding the strength of association between exposure and outcome but cannot establish a cause-effect relationship, there has been a need for experimental animal studies to confirm causality.”
“However,” Dr. Lein also added, “the criticism of much of the published animal data to date is that the exposures used have not faithfully mimicked human exposures. [This is because the] animals have been exposed to a subset of components that make up traffic-related air pollution and/or because animals have been exposed to very high concentrations of traffic-related air pollutants, often for relatively short periods of time.”
In fact, In Dr. Lein’s words, “Our study is relatively unique in that animals were exposed to ambient traffic-related air pollution in real time over the course of their lifetime, providing strong data to corroborate the epidemiologic data.”
Real-Time Impact
In order to properly perform the study properly and cohesively, the researchers exposed both male and female rats to either filtered air or polluted air. They did this for up to 14 months. They got polluted air from the busy tunnel in real time and delivered this straight to the animals without making any adjustments to the elements in the air.
The team then divided the rats into two groups: The first comprised those who expressed Alzheimer’s disease risk genes which were relevant to humans, and the other comprised wild-type rats. They made use of in 3-, 6-, 10-, and 15-month-old rats. Then, they quantified the expression of Alzheimer’s disease characteristics and carried out hyperspectral imaging and behavioral testing on the rodents.
The researchers discovered that having exposure to chronic traffic-related air pollution did, in fact, speed up and compound the traits that were relevant to Alzheimer’s disease in the rats who were genetically susceptible to this disease. Interestingly enough, they also saw the same effect in the second group of rats who were placed in a different area.
Dr. Lein explained to MNT, “Our data demonstrated that traffic-related air pollution decreases the time to onset and increases the severity of disease in rats who expressed genetic risk factors for Alzheimer’s disease.” She also suggests “that differences in exposure histories may contribute to the differing clinical profiles observed in individuals with similar genetic backgrounds.” The study came out with interesting facts, which she shared to MNT and said, that their “data suggest that even individuals who do not express [Alzheimer’s disease] risk genes are at increased risk [of] Alzheimer’s disease if they are chronically exposed to [traffic-related air pollution].”
Further Research Required
While the study produced interesting results, Dr. Heather Snyder, the vice president of medical and scientific relations at the Alzheimer’s Association, spoke to MNT about what they discovered. While she did appreciate how researchers behind this study are “looking at what might be a mechanism, what might be the biological underpinnings” that may work in accordance to the onset of Alzheimer’s disease, she also cautioned that it is too soon to say how these results will apply to humans. Snyder shared, “Alzheimer’s, and actually all causes of dementia, are […] complex diseases, and there are likely a number of things that are contributing to a person’s risk.”
While the connection between humans and animals have yet to be fully established, Dr. Lein looks forward to performing additional research. She said, “Our immediate goal is to determine which component(s) of the traffic-related air pollution mediate the effects on the aging brain.” Furthermore, she explained, “Is it the particulate matter, or the gases, or both? Are components from light duty (most cars) or heavy duty (trucks, including diesel trucks) more important in promoting Alzheimer’s disease phenotypes? The answer to this will be critically important for regulatory policymaking.”
Moreover, Dr. Lein and her colleagues in charge of this study are eager to fully comprehend how traffic-related air pollution promotes the development of characteristics connected to Alzheimer’s disease. They also want to look into the about windows of sensitivity of the disease asking, “Do early life exposures to traffic-related air pollution cause changes in the brain that manifest as [Alzheimer’s disease] phenotypes in old age? Or is it only exposures [in] mid-late life that are critical for increasing risk? Or do you really need chronic exposure across life to see the effects of traffic-related air pollution on the brain?”
Dr. Lein and her team do have a specific goal in mind. They want to identify the specific environmental factors that are closely linked to an increased risk of developing the disease. These, according to her, are easier to tackle than the genetic risk factors behind it. Further studies similar to this, for Dr. Lein, will help the ones in charge who“need data identifying specific environmental risk factors in order to enact meaningful policy changes.”
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