Long-term air pollution exposure linked to memory decline in Black adults

A recent study published in the journal Alzheimer’s & Dementia: Behavior & Socioeconomics of Aging provides evidence that long-term exposure to fine particulate air pollution may negatively affect specific types of memory in older Black adults. The research suggests that breathing polluted air over the course of more than a decade tends to harm semantic memory, which is the brain’s ability to recall general knowledge and facts. These findings highlight the importance of environmental factors in brain health and point to potential reasons behind racial disparities in dementia risk.

In the United States, Black adults experience rates of Alzheimer’s disease and other forms of dementia that are 1.5 to 2.0 times higher than those of White adults. Despite this elevated risk, Black adults have historically been underrepresented in environmental health research.

Stacey Alexeeff, a research scientist and biostatistician at the Kaiser Permanente Division of Research, explained the motivation behind the work. “Studies have shown that in the U.S., Black adults have much higher rates of dementia than White adults,” Alexeeff told PsyPost. “Black adults are also more likely to live in areas with higher levels of particulate air pollution than White adults.”

Alexeeff noted that focusing on these environmental factors could provide insight into broader public health patterns. “So, examining how air pollution impacts cognitive function among Black adults could help us understand these disparities,” Alexeeff said. “The Kaiser Permanente Northern California Study of Healthy Aging in African Americans (STAR) was designed to identify factors that impact brain aging among Black adults, which enabled us to examine air pollution over 17 years based on each person’s home address.”

To explore these questions, the scientists analyzed data from the STAR project, focusing on 740 Black adults between the ages of 53 and 94 who lived primarily in the San Francisco Bay Area. All the participants had completed health checkups in the past and had no previous diagnosis of dementia when they enrolled in the current study between 2017 and 2020. The researchers gathered residential addresses for each participant and linked these locations to high-resolution daily estimates of fine particulate air pollution.

The scientists focused on fine particulate matter, which consists of tiny particles that are 2.5 microns or smaller in width. “Air pollution in your neighborhood can affect your health,” Alexeeff said. “Small particles come from car exhaust, factories, and wildfires. When we breathe in those small particles, they can travel to the bloodstream and the brain.”

Alexeeff emphasized that while the respiratory and cardiovascular effects of pollution are well established, the neurological effects represent a newer area of scientific focus. “We already know a lot about how air pollution affects the heart and lungs, like increasing the risks of heart attacks and asthma,” Alexeeff said. “But there is a growing body of research that suggests long-term exposure to air pollution also affects how the brain functions.”

The researchers calculated the average amount of pollution each person was exposed to over three specific timeframes, including a five-year, ten-year, and seventeen-year period. During the study, each participant completed a detailed assessment to measure three distinct areas of cognitive ability. These included semantic memory, verbal episodic memory, and executive function.

The data provides evidence that greater long-term exposure to fine particulate air pollution is associated with lower scores in semantic memory. Specifically, the authors found that a five-microgram per cubic meter increase in pollution exposure over seventeen years was linked to a drop of 0.61 standard deviations in semantic memory performance. The five-year and ten-year exposure averages showed similar trends, but the associations were strongest over the seventeen-year timeframe.

“Prior research has shown that aging affects different aspects of our brain function in different ways,” Alexeeff said. “So, we knew it was important to look at each type of brain function separately, but we didn’t know what we would find. Interestingly, we found that long-term exposure to air pollution was associated with lower semantic memory, but not with other types of brain function.”

To put this into perspective, the researchers compared this pollution-related decline in memory to the natural aging process. “In fact, people living in areas with high air pollution for 17 years had worse semantic memory than those living in cleaner areas, and the difference was larger than what we’d expect from roughly a decade of aging,” Alexeeff said.

These prolonged effects indicate that the environment shapes cognitive trajectories in ways that require a sustained view. “This study is an important contribution to our understanding of the long-term impacts particle air pollution has on our health,” Alexeeff said. “Air pollution affects multiple systems in the body, and our findings suggest that exposures may continue to influence health more than a decade later.”

Because individual choices are often limited by socioeconomic factors, the researchers point out that systemic changes are needed. “Our study examined exposure to pollution over long time periods of 5, 10 and 17-years,” Alexeeff said. “If you live in an area with high levels of particle pollution, it’s hard to reduce your exposure through individual actions alone because most people can’t easily move to a different neighborhood.”

“There are steps people can take, like using a home air filter to reduce indoor exposure to small particles,” Alexeeff said. “But it takes policy solutions at a much larger scale to ensure that everyone in every neighborhood has clean air to breathe.”

The authors acknowledge a few potential misinterpretations and limitations. Because the study only included Black participants, it is not possible to directly compare these findings with other racial or ethnic groups within the same study framework. The findings highlight a specific risk factor for Black adults but do not determine if this population is uniquely vulnerable to pollution compared to others.

Another limitation involves the tracking of residential addresses over time. The researchers used addresses collected at specific ages, which means they did not have exact dates for when participants might have moved from one home to another. They also did not have information on how much time the participants spent outdoors or away from their homes, which could influence their actual day-to-day exposure to polluted air.

Future research should aim to track individual cognitive decline over time and differentiate between the various sources of air pollution. “The next steps are to look at whether particle pollution from say, a fire, causes more cognitive harm than particle pollution in car exhaust or in what is expelled from a factory,” Alexeeff said. Understanding exactly how specific types of dirty air affect brain functions will help public health officials anticipate future medical needs and design targeted interventions.

The study, “Particulate air pollution and domain-specific cognition among Black adults,” was authored by Stacey E. Alexeeff, Chinomnso N. Okorie, Paola Gilsanz, Joel Schwartz, Amanda J. Goodrich, Ai-Lin Tsai, Rachel A. Whitmer, Kelly M. Bakulski, Scarlet Cockell, and Kathryn C. Conlon.