People living in certain areas of the United States with high levels of air pollution are at increased risk of dementia, a new study has found.
The study was published in the journal on Monday JAMA Internal Medicineexamined data from 27,857 study participants from 1998 to 2016. About 15%, or 4,105, developed dementia during the study period, and all lived in areas of the United States with higher concentrations of particulate pollution than those who did not develop dementia. researchers discovered. The study authors said this was the first nationally representative study of the potential impact of particulate pollution on dementia in the United States, and that the association with dementia was strongest in areas contaminated by agriculture and wildfires. Stated.
The study authors said it was important to note that these associations were observed even at pollution levels below current national air quality standards.
Particulate pollution, also known as PM2.5 or particulate matter, is a mixture of solids and droplets suspended in the air, according to the United States. Environmental Protection Agency. It can appear in the form of dirt, dust, soot, smoke, etc. Particulate matter can come from coal- and natural gas-fired plants, automobiles, agriculture, dirt roads, construction sites, and wildfires.
Most previous research on this issue has focused primarily on particulate pollution from fossil fuels. However, new research suggests that the association with dementia appears to be strongest for pollution associated with agriculture and wildfires, although other sources such as traffic and coal burning may also arise.
“Both Boya and I were surprised when the names of agriculture and wildfires first popped up,” said Dr Sarah Dubowski Adder. associate chair I worked on this study with a team that included Dr. Boya Chan, PhD in Epidemiology and Fellow at the University of Michigan School of Public Health.
“In retrospect, this makes a lot of sense. Mainly the fact that we’re looking at effects on the brain and knowing that agriculture uses a lot of pesticides. Because there is,” Adal said.
Pesticides are neurotoxic to animals, so particles in agricultural pollution could also affect human brains, she said. When it comes to wildfires, smoke doesn’t just come from burning trees. Houses, petrol stations, etc. also burn, resulting in particulate pollution that people inhale.
Particulate contamination is especially deadly. PM2.5 teeth Very little — 1/20 the width of a human hair — means hair can pass through the body normal defense. Instead of being exhaled when you exhale, it can lodge deep in your lungs or enter your bloodstream.
Particles can cause irritation and inflammation and cause respiratory problems. Studies show that long-term exposure to particulate contamination can can also cause Cancer, depression, breathing problems, various heart problems.
“the same as tobaccoThere’s no such thing as a good inhalable particle,” said Caleb Finch, Ph.D., professor at the University of Southern California and ARCO/William F. Kieschnick Professor of Neurobiology of Aging, who was not involved in the new study. do not have. “Nearly all effects of air pollution are also affected by cigarette smoke.”
More than 55 million people worldwide have dementia, and more than 10 million develop dementia each year. who. the effects of aging, other health problems The number is expected to increase significantly, as are obesity, smoking and hypertension. in 2021The Alzheimer’s Association said rising air pollution levels and rising numbers of people with dementia around the world should be treated as a serious public health crisis.
The new study can’t pinpoint the exact mechanism linking particle pollution and dementia, but scientists have several theories.
These tiny particles of pollution can enter the brain through the nose and cause neuronal cell death associated with dementia. Particulate contamination may also alter inflammatory proteins that act on the brain.
Dr. Masashi Kitazawa, an Associate Professor Environmental and occupational health researchers at the University of California, Irvine speculated that pollution may have an indirect effect. scientists know Caused by exposure to particulate contamination heart condition For example, you have blood vessel problems, both of which can put you at risk for Alzheimer’s and dementia.
“Whether it caused cardiovascular failure and reduced oxygen supply to the brain, which caused the progression of dementia, or whether PM entered the brain and caused a neurotoxic response? We don’t know yet.” Kitazawa said he was not involved in the new research.
It’s also important to note that while the study shows a correlation, it doesn’t show that air pollution directly causes dementia, he said.
“I don’t want the general public to panic,” Kitazawa said. Rather, this relationship requires further research.
Kitazawa and Finch’s lab is one of several researchers working to understand this connection. Finch said his study showed that air particles from fossil fuels can increase levels of amyloid protein in the brain, which is linked to Alzheimer’s disease.
“Overall, I think there are reasons to take the association seriously,” he said.
other the study They found similar associations between specific pollution and dementia.
a 2016 survey A study of 6.6 million Canadians found that those living within 164 feet of a highway were 7% more likely to develop dementia than those living 984 feet away. Microparticulate matter levels were found to be up to 10 times lower.
a study in england They found that adults living in environments with the highest annual concentrations of air pollution had a 1.4-fold increased risk of dementia compared to adults living in environments with the lowest annual concentrations.
the study In California, they found that older women exposed to high levels of air pollution performed worse on cognitive tests than women exposed to low levels of air pollution. Scans also showed a shrinkage of areas of the brain normally affected by Alzheimer’s disease.
Even if there is no clear link between dementia and particulate pollution, given all the other health problems air pollution can cause, people need to act now to limit their exposure. Study co-author Zhang thinks so.
Many countries have laws and incentives to reduce air pollution, but almost everyone in the world breathes more air than the World Health Organization. limit of air qualitythe number of “extremely unhealthy” and “dangerous” air quality day It has grown over the years, largely due to the climate crisis. In 2011, USA aloneA recent study found that exposure to this type of pollution resulted in 107,000 extra premature deaths from all causes.
Measures to reduce personal exposure include using air purifiers at home and wearing a mask if going out in wildfire smoke, Zhang said.
At the policy level, governments may restrict their use if the problem turns out to be pesticides. “This is good for welfare and will be a global action to reduce people’s exposure to radiation,” Zhang said.
Study co-author Adder hopes the study will encourage broader change.
“I hope this is another reason to motivate people to take action against climate change and think about how to slow the progression of climate change,” she said. “We are seeing so many tragic examples of what is happening now.”