For years, the two patients visited the Penn Memory Center at the University of Pennsylvania, where researchers and doctors follow people with cognitive decline as they age and, in turn, a group with normal cognitive abilities.
Both patients, a man and a woman, agreed to donate their brains for research. “An incredible gift,” said Dr. Edward Lee, neurologist and director brain bank from the university's Perelman School of Medicine. “They were both very interested in helping us understand Alzheimer's disease.”
The man who died at age 83 from dementia lived with paid caregivers in Philadelphia's Center City neighborhood. An autopsy revealed large amounts of amyloid plaques and tau tangles—proteins associated with Alzheimer's disease—that had spread throughout the brain.
Investigators also found infarcts, small spots of damaged tissue, indicating he had suffered multiple strokes.
In contrast, the woman who died at age 84 from brain cancer “showed almost no signs of Alzheimer's disease,” Lee said. “We tested him year after year and he never had any cognitive problems.”
The man lived a few blocks from Interstate 676, which runs through downtown Philadelphia. The woman is a few miles away, in the suburb of Gladwin, surrounded by woods and a country club.
The amount of air pollution she was exposed to – specifically levels of fine particles known as PM2.5 – was less than half of what the man received. Was it a coincidence that he developed severe Alzheimer's disease while she remained sane?
Probably not, given growing evidence that chronic exposure to PM2.5—a neurotoxicant—not only damages the lungs and heart, but is also linked to dementia.
“The air quality where you live affects how you think,” said Lee, the study's lead author. recent article published in JAMA Neurologyone of several large-scale studies published in recent months showing a link between PM2.5 and dementia.
Scientists have been studying this connection for at least a decade. Influential in 2020 Lancet Commission The Lancet panel included air pollution in its list of modifiable risk factors for dementia, along with common problems such as hearing loss, diabetes, smoking and high blood pressure.
The findings come just as the federal government is reversing measures taken by previous administrations to reduce air pollution by shifting away from fossil fuels to renewable energy sources.
“'Drain, baby, train' is just the wrong approach,” said Dr. John Balmes, a spokesman for the American Lung Association and a researcher on the health effects of air pollution at the University of California, San Francisco.
“All of these decisions will lead to decreased air quality and increased mortality and morbidity. Dementia is one of those consequences,” Balmes added, referring to recent environmental measures taken by the White House.
Of course, there are many factors that contribute to dementia. But the role of particles – particulate matter or microscopic droplets present in the air – is receiving increasing attention.
These particles come from many sources: emissions from power plants and home heating, industrial gases, vehicle exhaust and, increasingly, smoke from wildfires.
Of the various particle sizes, PM2.5 “appears to be the most harmful to human health” because it is one of the smallest, Lee said. It is easily inhaled, enters the bloodstream and circulates throughout the body; It can also travel directly from the nose to the brain.
The University of Pennsylvania study, the largest autopsy study of people with dementia to date, included more than 600 brains donated over two decades.
Previous studies of the relationship between environmental pollution and dementia were based primarily on epidemiological studies. Now, “we're linking what we actually see in the brain to exposure to pollutants,” Lee explained. “We're going deeper.”
Study participants underwent years of cognitive testing at the Pennsylvania Memory Center. Using an environmental database, the researchers were able to calculate PM2.5 exposure based on their home addresses.
The scientists also developed a matrix to measure the severity of brain damage caused by Alzheimer's disease and other dementias.
Lee's team concluded that “the greater the exposure to PM2.5, the greater the severity of Alzheimer's disease,” he said. The odds of finding more severe Alzheimer's disease at autopsy were nearly 20% higher among those who lived in areas with high levels of PM2.5.
Another research group recently reported connection between PM2.5 exposure and dementia with Lewy bodies, which includes dementia associated with Parkinson's disease. Generally considered the second most common type after Alzheimer's disease, Lewy body dementia accounts for 5% to 15% of cases.
In the largest epidemiological study to date of pollution and dementia, researchers analyzed the records of more than 56 million people on traditional Medicare between 2000 and 2014, comparing their first hospitalizations for neurodegenerative diseases with PM2.5 levels, according to zip codes.
“Chronic exposure to PM2.5 was associated with hospitalization for Lewy body dementia,” said Xiao Wu, study author and biostatistician at Columbia University's Mailman School of Public Health.
After accounting for socioeconomic differences and other factors, the researchers found that PM2.5 hospitalization rates were 12% higher in U.S. counties with the worst PM2.5 concentrations compared to counties with the lowest levels.
To confirm their findings, the researchers administered PM2.5 nasally to laboratory mice, which after 10 months showed “obvious dementia-like impairments,” lead author Xiaobo Mao, a neuroscientist at Johns Hopkins University School of Medicine, wrote in an email.
The mice got lost in labyrinths that they had previously easily navigated. They used to build their nests quickly and carefully; After the exhibition, they did it in a careless and disorganized manner. At autopsy, their brains showed atrophy and accumulation of the protein alpha-synuclein, which is associated with Lewy bodies in the human brain, Mao said.
Third analysispublished this summer in Lancetincluded 32 studies conducted in Europe, North America, Asia and Australia. It also found that “a diagnosis of dementia is significantly associated with long-term exposure to PM2.5” and several other pollutants.
Whether outdoor air pollution (called environmental pollution) increases the risk of dementia through inflammation or other physiological mechanisms is a question that still requires more research to answer.
Although air pollution in the United States has declined over the past two decades, scientists are calling for even stricter policies to ensure cleaner air. “People say improving air quality is expensive,” Lee said. “So is caring for people with dementia.”
However, President Donald Trump returned to power with a promise increase production and use of fossil fuelsand slow the transition to renewable energy. Your administration tax breaks canceled for solar installations and electric vehicles, Balmes noted, adding: “They are in favor of continuing to burn coal for energy production.”
The government also halted new offshore wind projectsadvertising oil drilling and gas in Alaska's Arctic National Wildlife Refuge and has taken steps to stop California plan switch to electric vehicles by 2035. (The state challenged this action in court.)
“If the policy goes in the opposite direction, with air pollution increasing, it poses a big risk to the health of older people,” Wu warned.
Last year, under the Biden administration, the Environmental Protection Agency (EPA) established annual standards more stringent standards for PM2.5, noting that “available scientific evidence and technical information indicate that current standards may not be sufficient to protect public health and welfare as required by the Clean Air Act.”
In March new EPA director announced that the agency would “reevaluate” these stricter standards.
The New Old Age is created in collaboration with New York Times.
