Air Pollution Can Affect Mental Health of Older Adults

A new study led by researchers at UCL has found that long-term exposure to high levels of air pollution can affect brain health in older adults in England. Published in The Journals of Gerontology: Series A, the study found that exposure to nitrogen dioxide (NO₂) and particulate matter (PM_2.5) was associated with lower levels of key cognitive abilities, particularly language skills.

How Air Pollution Affects the Brain

Nitrogen dioxide enters the atmosphere mainly through the combustion of fuel and comes from emissions from vehicles such as cars, trucks and buses, as well as from power plants and lawnmowers. Outdoor PM_2.5 pollution often comes from the combustion of gasoline, oil, diesel fuel or wood and consists of tiny particles that can be inhaled deep into the lungs. The researchers analyzed data from 1,127 adults aged 65 and older who participated in the ELSA Harmonized Cognitive Assessment Protocol (ELSA-HCAP) in 2018. The team examined air pollution exposure over an eight- to 10-year period (2008–2017) and assessed the participants’ memory, executive functions (i.e. making plans, solving problems and adapting to new situations), language and general cognitive function.

Participants completed a battery of well-established neurocognitive memory tests, such as the East Boston Memory Test and the Wechsler Memory Scale, as well as immediate and delayed recall, backwards counting, and shape drawing tasks. The results showed that people living in areas with the highest levels of NO₂ and PM_2.5 performed worse on cognitive tests than people living in areas with average levels of pollutants. The most convincing evidence of an association was observed in language skills, with people in the most polluted areas scoring in the bottom third on the cognitive tests administered. The study also found that different sources of air pollution had different effects on cognitive health. For example, a strong link was found between air pollution from industry and heating and burning fuels (such as coal and oil) and poorer language performance (i.e. the ability to quickly access and produce words).

The authors did not explore the reasons for their findings, but suspect it may be because increased air pollution was most strongly associated with impairment in the temporal lobe (the part of the brain essential for language and semantic fluency). Further research is needed to understand these associations. Lead author Dr. Giorgio Di Gessa (UCL Epidemiology & Health) said: “Our study shows that air pollution is not only harmful to the lungs and heart, but also to brain health, especially when people are exposed to high levels for long periods. “We found the most consistent associations in language abilities, which could indicate that certain pollutants have a specific effect on certain cognitive processes.”

Limitations of the Study

The researchers therefore call on policymakers to tighten air quality regulations, particularly in areas with persistently high levels of air pollution, to protect brain health in the face of an ageing population. Deputy leader of the ELSA study, Professor Paola Zaninotto (UCL Epidemiology & Health), said: “By tracking air pollution over 10 years with high-quality data, our research provides solid evidence that prolonged exposure to pollutants damages the brain.”

The air pollution data used in the study only covers 10 years, which may not accurately reflect lifetime exposure. Furthermore, annual averages of pollution levels were used, so short-term effects of high exposure are missing. In addition, the study sample is small and limited to England, which may not reflect broader trends.