Living in an area that has high levels of air pollution may affect certain ways the brain works, a new Kaiser Permanente study found.
“Our findings add to a growing body of research that suggests pollution doesn’t only damage the heart and lungs, but it also affects how the brain functions,” said lead author Stacey E. Alexeeff, PhD, a research scientist at the Kaiser Permanente Division of Research.
The new study was published in Alzheimer’s & Dementia: Behavior & Socioeconomics of Aging, a journal of the Alzheimer’s Association. The research included 740 adults enrolled in the ongoing Kaiser Permanente Study of Healthy Aging in African Americans (STAR). Launched in 2017, the STAR study aims to identify factors that impact healthy brain aging among San Francisco Bay Area-based Black adults who are 50 and older. It is one of the first studies to look at whether pollution may increase dementia risk in Black adults.
“Previous studies have found that in the U.S., Black adults have significantly higher rates of dementia than non‑Hispanic, White adults have,” said co-author Paola Gilsanz, ScD, a research scientist at the Division of Research, who is co-leading the STAR study. “It is important to look at reasons for this disparity, and environmental exposures, like air pollution, is one of multiple factors we are exploring.”
Measuring memory
The study measured 3 specific areas of cognitive ability: semantic memory (general accumulated knowledge), verbal episodic memory (ability to recall words and stories), and executive function (planning and multitasking).
Daily air pollution data and each STAR participant’s home address was used to compute individual 5-year, 10-year, and 17-year average exposures to a type of fine particulate pollution called PM2.5. Small particle pollution has the potential to affect cognitive function because it can get into the bloodstream and the brain.
Particle pollution is measured in microns. To illustrate the smallness, about 25,000 microns equal an inch. These particles are released in exhaust from cars, trucks, and other vehicles, and from burning wood, heating oil, and coal. Factories, power plants, and forest fires are also a cause.
The study showed exposure to higher PM2.5 levels over 17 years was associated with lower semantic memory. No association was seen between air particle pollution and executive function or verbal episodic memory.
“Looking at each cognitive domain separately is important, because different risk factors can affect each domain differently,” said Alexeeff. “Because we did not use only one measure of cognition, we were able to learn that long‑term air pollution exposure affects semantic memory but not executive function or verbal episodic memory.”
The impact on under-resourced communities
Exposure to air pollution has been shown to cause greater harm to under-resourced communities. In addition, studies led by the U.S. Environmental Protection Agency have found that people who are Black, Latino, or Asian are more likely to live in areas with higher levels of particulate air pollution.
The new study adds to a growing body of research looking at how exposure to small particle pollution affects cognitive function and risk of dementia.
“This study is an important contribution to our understanding of the long-term impacts particle air pollution has on our health,” said Alexeeff. “Air pollution affects multiple systems in the body, and our findings suggest that exposures may continue to influence health more than a decade later.”
