Breathing dirty air harms more than your lungs. It may also lead to cognitive decline, making you worse at maths and damaging your language skills.
Xiaobo Zhang at Peking University in Beijing and his colleagues compared cognitive test scores of 31,955 people in China over the age of 10 in 2010 and 2014, and matched the scores with official air quality data from the city where each test subject lived. They found that air pollution impaired both mathematics and verbal test performances, and the decline likely becomes more significant with long term exposure.
Men also experienced greater decline in verbal test scores than women. Zhang says this might be because air pollution can reduce the density of the brain’s white matter – tissue associated with language skills. Previous studies have shown that men in tend to use less white matter than women during intelligence tests, which could make them more susceptible to such damage.
It might have an outsized impact on elderly people living in polluted areas, Zhang says. “Cognitive decline may affect elderly people’s ability in running daily errands and making high-stake decisions,” he says. “It’s also a risk factor for many diseases such as Alzheimer’s and dementia.”
Air pollution may damage the brain through several pathways at once, Zhang says. Other research has shown that pollutants in the air can carry toxins into the brain, insufficient oxygen supply may impair cognitive functions, and prolonged exposure to unclean air can lead to neurological inflammation and disease. Certain pollutants may also lead to psychiatric stress and depression, which can affect cognitive performance.
“Cognitive decline imposes a huge burden on the society,” Zhang says. “Although the air quality is getting better, which already came with high economic cost, there are bigger problems down the road.”
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1809474115
First published at New Scientist, Monday 27 August 2018.