For years, the two patients had come to the Penn Memory Center at the University of Pennsylvania, where doctors and researchers follow people with cognitive impairment as they age, as well as a group with normal cognition.<\/p>\n
Both patients, a man and a woman, had agreed to donate their brains after they died for further research. \u201cAn amazing gift,\u201d said Edward Lee, the neuropathologist who directs the brain bank<\/a> at the university\u2019s Perelman School of Medicine. \u201cThey were both very dedicated to helping us understand Alzheimer\u2019s disease.\u201d<\/p>\n The man, who died at 83 with dementia, had lived in the Center City neighborhood of Philadelphia with hired caregivers. The autopsy showed large amounts of amyloid plaques and tau tangles, the proteins associated with Alzheimer\u2019s disease, spreading through his brain.<\/p>\n Researchers also found infarcts, small spots of damaged tissue, indicating that he had suffered several strokes.<\/p>\n By contrast, the woman, who was 84 when she died of brain cancer, \u201chad barely any Alzheimer\u2019s pathology,\u201d Lee said. \u201cWe had tested her year after year, and she had no cognitive issues at all.\u201d<\/p>\n The man had lived a few blocks from Interstate 676, which slices through downtown Philadelphia. The woman had lived a few miles away in the suburb of Gladwyne, Pennsylvania, surrounded by woods and a country club.<\/p>\n The amount of air pollution she was exposed to \u2014 specifically, the level of fine particulate matter called PM2.5 \u2014 was less than half that of his exposure. Was it a coincidence that he had developed severe Alzheimer\u2019s while she had remained cognitively normal?<\/p>\n With increasing evidence that chronic exposure to PM2.5, a neurotoxin, not only damages lungs and hearts but is also associated with dementia, probably not.<\/p>\n \u201cThe quality of the air you live in affects your cognition,\u201d said Lee, the senior author of a recent article in JAMA Neurology<\/a>, one of several large studies in the past few months to demonstrate an association between PM2.5 and dementia.<\/p>\n Scientists have been tracking the connection for at least a decade. In 2020, the influential Lancet Commission added air pollution<\/a> to its list of modifiable risk factors for dementia, along with common problems like hearing loss, diabetes, smoking, and high blood pressure.<\/p>\n Yet such findings are emerging when the federal government is dismantling efforts by previous administrations to continue reducing air pollution by shifting from fossil fuels to renewable energy sources.<\/p>\n \u201c\u2018Drill, baby, drill\u2019 is totally the wrong approach,\u201d said John Balmes, a spokesperson for the American Lung Association who researches the effects of air pollution on health at the University of California-San Francisco.<\/p>\n \u201cAll these actions are going to decrease air quality and lead to increasing mortality and illness, dementia being one of those outcomes,\u201d Balmes said, referring to recent environmental moves by the White House.<\/p>\n Many factors contribute to dementia, of course. But the role of particulates \u2014 microscopic solids or droplets in the air \u2014 is drawing closer scrutiny.<\/p>\n Particulates arise from many sources: emissions from power plants and home heating, factory fumes, motor vehicle exhaust, and, increasingly, wildfire smoke.<\/p>\n Of the several particulate sizes, PM2.5 \u201cseems to be the most damaging to human health,\u201d Lee said, because it is among the smallest. Easily inhaled, the particles enter the bloodstream and circulate through the body; they can also travel directly from the nose to the brain.<\/p>\n The research at the University of Pennsylvania, the largest autopsy study to date of people with dementia, included more than 600 brains donated over two decades.<\/p>\n Previous research on pollution and dementia mostly relied on epidemiological studies to establish an association. Now, \u201cwe\u2019re linking what we actually see in the brain with exposure to pollutants,\u201d Lee said, adding, \u201cWe\u2019re able to do a deeper dive.\u201d<\/p>\n The study participants had undergone years of cognitive testing at Penn Memory. With an environmental database, the researchers were able to calculate their PM2.5 exposure based on their home addresses.<\/p>\n The scientists also devised a matrix to measure how severely Alzheimer\u2019s and other dementias had damaged donors\u2019 brains.<\/p>\n Lee\u2019s team concluded that \u201cthe higher the exposure to PM2.5, the greater the extent of Alzheimer\u2019s disease,\u201d he said. The odds of more severe Alzheimer\u2019s pathology at autopsy were almost 20% greater among donors who had lived where PM2.5 levels were high.<\/p>\n Another research team recently reported a connection<\/a> between PM2.5 exposure and Lewy body dementia, which includes dementia related to Parkinson\u2019s disease. Generally considered the second most common type after Alzheimer\u2019s, Lewy body accounts for an estimated 5% to 15% of dementia cases.<\/p>\n In what the researchers believe is the largest epidemiological study to date of pollution and dementia, they analyzed records from more than 56 million beneficiaries with traditional Medicare from 2000 to 2014, comparing their initial hospitalizations for neurodegenerative diseases with their exposure to PM2.5 by ZIP codes.<\/p>\n \u201cChronic PM2.5 exposure was linked to hospitalization for Lewy body dementia,\u201d said Xiao Wu, an author of the study and a biostatistician at the Mailman School of Public Health at Columbia University.<\/p>\n After controlling for socioeconomic and other differences, the researchers found that the rate of Lewy body hospitalizations was 12% higher in U.S. counties with the worst concentrations of PM2.5 than in those with the lowest.<\/p>\n To help verify their findings, the researchers nasally administered PM2.5 to laboratory mice, which after 10 months showed \u201cclear dementia-like deficits,\u201d senior author Xiaobo Mao, a neuroscientist at the Johns Hopkins School of Medicine, wrote in an email.<\/p>\n The mice got lost in mazes that they had previously dashed through. They had earlier built nests quickly and compactly; now their efforts were sloppy, disorganized. At autopsy, Mao said, their brains had atrophied and contained accumulations of the protein associated with Lewy bodies in human brains, called alpha-synuclein.<\/p>\n A third analysis<\/a>, published this summer in The Lancet, included 32 studies conducted in Europe, North America, Asia, and Australia. It also found \u201ca dementia diagnosis to be significantly associated with long-term exposure to PM2.5\u201d and to certain other pollutants.<\/p>\n Whether so-called ambient air pollution \u2014 the outdoor kind \u2014 increases dementia because of inflammation or other physiological causes awaits the next round of research.<\/p>\n Although air pollution has declined in the United States over two decades, scientists are calling for still stronger policies to promote cleaner air. \u201cPeople argue that air quality is expensive,\u201d Lee said. \u201cSo is dementia care.\u201d<\/p>\n President Donald Trump, however, reentered office vowing to increase the extraction and use of fossil fuels<\/a> and to block the transition to renewable energy. His administration has rescinded tax incentives<\/a> for solar installations and electric vehicles, Balmes noted, adding, \u201cThey\u2019re encouraging continuing to burn coal for power generation.\u201d<\/p>\n The administration has halted new offshore wind farms<\/a>, announced oil and gas drilling<\/a> in the Arctic National Wildlife Refuge in Alaska, and moved to stop California\u2019s plan<\/a> to transition to electric cars by 2035. (The state has challenged that action in court.)<\/p>\n \u201cIf policy goes in the opposite direction, with more air pollution, that\u2019s a big health risk for older adults,\u201d Wu said.<\/p>\n Last year, under the Biden administration, the Environmental Protection Agency set tougher annual standards<\/a> for PM2.5, noting that \u201cthe available scientific evidence and technical information indicate that the current standards may not be adequate to protect public health and welfare, as required by the Clean Air Act.\u201d<\/p>\n In March, the EPA\u2019s new chairman announced<\/a> that the agency would be \u201crevisiting\u201d those stricter standards.<\/p>\n The New Old Age is produced through a partnership with <\/em>The New York Times<\/em><\/a>.<\/em><\/p>\n\n KFF Health News<\/a> is a national newsroom that produces in-depth journalism about health issues and is one of the core operating programs at KFF\u2014an independent source of health policy research, polling, and journalism. Learn more about KFF<\/a>.<\/p>\nUSE OUR CONTENT<\/h3>\n