Air pollution, specifically fine particulate matter known as PM2.5, has been linked to an increased risk of Alzheimer’s disease and other forms of dementia, according to a groundbreaking study from the University of Pennsylvania. The research highlights the potential cognitive risks associated with chronic exposure to air pollutants, raising urgent questions about public health policies aimed at reducing air quality deterioration.
At the Penn Memory Center, researchers have conducted extensive studies on individuals with cognitive impairment. Two notable cases involved a man who passed away at 83 due to dementia and a woman who died at 84 from brain cancer. The autopsy of the man revealed significant Alzheimer’s-related brain changes, including amyloid plaques and tau tangles, alongside signs of previous strokes. In contrast, the woman showed minimal Alzheimer’s pathology, despite having lived in a location with significantly lower PM2.5 exposure.
The man’s residence near Interstate 676 in downtown Philadelphia exposed him to higher levels of air pollution compared to the woman’s home in the suburb of Gladwyne, Pennsylvania, surrounded by green spaces. “The quality of the air you live in affects your cognition,” stated Edward Lee, the neuropathologist who led the study published in JAMA Neurology. This research builds on a decade of evidence linking PM2.5 to cognitive decline, further solidifying air pollution as a modifiable risk factor for dementia.
The Lancet Commission recognized air pollution as a significant risk factor for dementia in its influential 2020 report, alongside other known factors such as diabetes and smoking. Yet, current U.S. federal policies have begun to reverse efforts aimed at reducing air pollution, raising concerns among health experts. “All these actions are going to decrease air quality and lead to increasing mortality and illness, dementia being one of those outcomes,” warned John Balmes from the American Lung Association.
The study from the University of Pennsylvania analyzed over 600 brain donations and years of cognitive testing. Researchers were able to correlate the donors’ PM2.5 exposure with the extent of Alzheimer’s pathology observed in their brains. They found that the probability of severe Alzheimer’s pathology increased by nearly 20% for individuals living in areas with high PM2.5 concentrations.
A separate study from Columbia University highlighted the connection between PM2.5 exposure and Lewy body dementia, which accounts for an estimated 5% to 15% of dementia cases. This comprehensive analysis utilized records from over 56 million Medicare beneficiaries to establish a clear link between chronic PM2.5 exposure and hospitalization for neurodegenerative diseases.
Further supporting this research, laboratory studies conducted on mice exposed to PM2.5 demonstrated significant cognitive impairments. After ten months, these mice exhibited behaviors indicative of dementia, such as difficulty navigating mazes. Their autopsies revealed brain atrophy and accumulations of proteins associated with Lewy body dementia.
A third analysis published in The Lancet reviewed 32 studies across various regions, confirming that long-term exposure to PM2.5 and other pollutants correlates significantly with dementia diagnoses. Researchers are now investigating whether inflammation or other physiological responses to air pollution contribute to cognitive decline.
Despite a decline in air pollution levels in the United States over the past two decades, experts argue for stronger regulations to ensure cleaner air. “So is dementia care,” noted Lee, emphasizing the economic burden of neglecting air quality. Recent policy shifts under the Biden administration have aimed to tighten annual standards for PM2.5, recognizing the need to protect public health.
As environmental regulations face challenges, including efforts to expand fossil fuel use, the implications for older adults and those at risk for dementia remain critical. Balmes added, “If policy goes in the opposite direction, with more air pollution, that’s a big health risk for older adults.” The ongoing dialogue around air quality and health will likely shape future public health initiatives and regulatory frameworks.
