Summary: Long-term exposure to nitrogen dioxide and fine particulate matter may harm cognitive health, particularly language ability, in older adults. In a new study of individuals aged 65 and over, those living in England’s most polluted areas consistently scored lower on cognitive assessments, especially in language-based tasks.
The findings suggest air pollution may impair specific brain regions, such as the temporal lobe, which governs language processing. Researchers call for stronger air quality regulations to protect aging populations from cognitive decline.
Key Facts:
- Language Impact: Older adults exposed to high levels of NO₂ and PM2.5 showed the most significant declines in language-related cognitive tasks.
- Pollution Sources Matter: Emissions from industry, home heating, and fuel combustion were strongly linked to poorer language performance.
- Brain Region Link: Findings suggest air pollution may affect the temporal lobe, essential for semantic fluency and language.
Source: UCL
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 UCL researchers.
The research, published in The Journals of Gerontology: Series A, 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 analysed data from 1,127 adults aged 65 and over who took part in the ELSA Harmonised Cognitive Assessment Protocol (ELSA-HCAP) in 2018.
The team examined exposure to air pollution over an eight to 10 year period (2008-2017) 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.
Lead author Dr Giorgio Di Gessa (UCL Epidemiology & Health) said: “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.
“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.
Deputy director of the ELSA study, Professor Paola Zaninotto (UCL Epidemiology & Health), said: “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 brains.”
ELSA is funded by the National Institute on Aging and by UK Government Departments coordinated by the National Institute for Health and Care Research (NIHR).
Study limitations
The air pollution data used in the study only covers 10 years, which may not accurately represent lifetime exposure.
Meanwhile, yearly averages of pollution levels were used, missing short-term high exposure impacts.
Additionally, the study sample is small and limited to England, which may not reflect broader trends.
About this pollution and cognition research news
Author: Poppy Tombs
Source: UCL
Contact: Poppy Tombs – UCL
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Cognitive performance and long-term exposure to outdoor air pollution: Findings from the Harmonised Cognitive Assessment Protocol sub-study of the English Longitudinal Study of Ageing (ELSA-HCAP)” by Giorgio Di Gessa et al. The Journals of Gerontology Series A
Abstract
Cognitive performance and long-term exposure to outdoor air pollution: Findings from the Harmonised Cognitive Assessment Protocol sub-study of the English Longitudinal Study of Ageing (ELSA-HCAP)
Background
Although air pollution is associated with worse cognitive performance, whether these relationships differ by cognitive domain and which sources of air pollution are particularly detrimental to cognition remains understudied.
This study examined associations between cognitive scores across three domains in older adults and 8-10 years of exposure to air pollutants (NO2, total PM2.5, and PM2.5 from different emission sources).
Methods
We used data from the 2018 Harmonized Cognitive Assessment Protocol sub-study of the English Longitudinal Study of Ageing (N=1,127). Outdoor concentrations of each pollutant were estimated for 2008/10-2017 and summarised using means and group-based trajectories.
Linear regression models were used to assess long-term air pollution exposure relationships with memory, executive function, language, and global cognitive function after adjustment for key individual and neighbourhood-level confounders.
Results
Associations between air pollution trajectories and cognition are mostly inverted j-shaped, with respondents exposed to the highest residential levels of NO2 and total PM2.5 having worse performance for global cognition [β=-0.241; 95%CI=(-0.46,-0.02) and β=-0.334; 95%CI=(-0.55,-0.12) respectively] than those exposed to average levels of pollution.
Similar associations were also found for executive function and memory (PM2.5 only), whereas more compelling dose-response evidence was found for language. Higher emissions from industry and residential combustion, as well as biofuel, coal, oil and natural gas combustion, were associated with worse language scores.
Conclusions
Air pollution and its sources have domain-specific associations with cognitive performance, with most consistent evidence observed for language. Continued efforts to reduce air pollution, particularly where levels are the highest, might benefit cognitive performance.
