Exposure to Air Pollution May Harm Our Brain Health as We Age

Long-term exposure to high levels of air pollution may harm the brain health of older adults in England, finds a new study led by University College London (UCL) researchers.

The research, published in the Gerontological Society of America’s The Journals of Gerontology: Series A: Biological Sciences and Medical Sciences, found that exposure to nitrogen dioxide (NO2) and fine particulate matter (PM2.5) is linked to lower scores in key cognitive abilities, particularly language skills.

NO2 mainly enters the atmosphere through fuel combustion, originating from emissions of vehicles like cars, trucks, and buses, as well as power plants and off-road machinery. PM2.5 pollution in outdoor air often originates from the combustion of gasoline, oil, diesel fuel, or wood, and consists of tiny particles that can be inhaled deeply into the lungs.

The researchers analyzed data from 1,127 adults aged 65 and over who took part in the English Longitudinal Study of Ageing (ELSA) Harmonised Cognitive Assessment Protocol in 2018.

The team examined exposure to air pollution over an eight-to-10 year period (2008 to 2017) and assessed participants’ memory, executive function (i.e. making plans, solving problems and adapting to new situations), language, and overall cognitive function.

Participants completed a range of well-established neurocognitive memory assessments such as the East Boston Memory Test and the Wechsler Memory Scale, alongside immediate and delayed recall, backwards counting tasks, and shape drawing.

The findings showed that individuals residing in areas with the highest levels of NO2 and PM2.5 performed worse on cognitive tests compared to those living in areas with average pollution levels. The most compelling evidence of association was observed in language skills, with individuals in the most polluted areas scoring in the bottom third of the cognitive tests performed.

The study also found that different sources of air pollution have varying effects on cognitive health. For example, pollution from industries, home heating, and combustion of fuels (like coal and oil) were strongly linked to poorer language performance (i.e. the ability to access and produce words quickly).

The authors did not examine the reasons behind their findings but suggest that this may be because increased air pollution exposure is most strongly associated with impairment in the temporal lobe (the part of the brain which is essential for language and semantic fluency). Further research is needed to understand these links.

"Our study shows that air pollution is not just harmful to the lungs and heart but also to brain health, especially when people are exposed to high levels for long periods,” said lead author Giorgio Di Gessa, PhD, of the UCL Department of Epidemiology and Public Health. “The most consistent links we found were with language ability, which may indicate that certain pollutants have a specific effect on particular cognitive processes."

Consequently, the researchers urge policymakers to strengthen air quality regulations, particularly in areas where pollution levels remain high, to help protect brain health as the population ages.

“By tracking pollution levels over a decade using high-quality data, our research provides robust evidence that sustained exposure to pollutants is damaging people’s brain,” said ELSA study Deputy Director Paola Zaninotto of the UCL Department of Epidemiology and Public Health.

ELSA is funded by the National Institute on Aging and by United Kingdom government departments coordinated by the UK National Institute for Health and Care Research.

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The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences is a peer-reviewed publication of the Gerontological Society of America (GSA), which was founded in 1945 and is the nation’s oldest and largest interdisciplinary organization focused on aging. It serves more than 6,000 members in over 50 countries. GSA’s vision, meaningful lives as we age, is supported by its mission to foster excellence, innovation, and collaboration to advance aging research, education, practice, and policy. GSA is home to the National Academy on an Aging Society (a nonpartisan public policy institute) and the National Center to Reframe Aging.