Breathing in traffic-related air pollution might increase your risk of developing age-related dementia, including Alzheimer's disease, a new study suggests.
In the study, published this month in the journal Environmental Health Perspectives, researchers at the University of California-Davis set up a rodent habitat near a busy traffic tunnel in Northern California. The scientists then exposed rats to either filtered air or polluted air direct from the tunnel for up to 14 months.
The rats were divided into two groups: Wild rats, then those that expressed Alzheimer's disease risk genes similar to humans. The researchers found that being exposed to chronic traffic-related air pollution accelerated the development of—and worsened—Alzheimer's-like symptoms in both groups.
"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," Dr. Pamela Lein, a professor of neurotoxicology at the University of California, Davis, told Medical News Today. She said the findings suggest that even people who aren't genetically predisposed to Alzheimer's may be at increased risk if they're chronically exposed to traffic-related air pollution.
Other Studies Show Link
Several other studies have suggested there may be a link between air pollution and dementia. A 2018 review of studies published in the Journal of Alzheimer's Disease analyzed 13 research papers and found that exposures to particulate matter, nitrogen dioxide, nitrous oxides, and carbon monoxide—all elements found in traffic-related air pollution—were linked to dementia. "Evidence is emerging that greater exposure to airborne pollutants is associated with increased risk of dementia," the researchers wrote.
What is Dementia?
Dementia is an umbrella term for many disorders that can cause changes to memory, thinking, and personality that interfere with a person's ability to function. Alzheimer's disease is the most common form of dementia; at least 5 million Americans are affected.
About 50 million people are living with dementia worldwide, and that number is expected to triple by 2050, as the population ages and people live longer.
What Are the Risk Factors For Dementia?
According to the CDC, the currently established risk factors for dementia include:
Age. This is the strongest risk factor. Mostly, people over age 65 are affected.
Race/ethnicity. African Americans are twice as likely, and Hispanics are 1.5 times more likely, to develop dementia than white people.
Poor heart health, including high blood pressure, high cholesterol, and smoking.
Traumatic brain injury.
More Study Needed
Both the researchers behind the rodent study and dementia experts have cautioned that the findings are preliminary. (Remember: Correlation doesn't equal causation, and animal studies don't necessarily correlate to humans.)
"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," said Heather Snyder, Ph.D., vice president of medical and scientific relations at the Alzheimer's Association.
The scientists who conducted the study have called for more research to determine how pollutants may affect the aging brain. And to ensure your health and the health of others, don't miss these Sure Signs You Had COVID and Didn't Know It.