Air pollution can damage the brain, Chinese researchers find in far-reaching national study
Lead author says smog could have a bigger impact on social welfare than previously thought
Just as air pollution impairs the lungs and reduces life expectancy, it also seems to harm the brain and cognition skills, especially among the elderly, a group of Chinese researchers has found.
In a study published in the journal Proceedings of the National Academy of Sciences in the United States on Monday, analysis of air quality readings and scores in nationwide maths and verbal tests suggests that exposure to air pollution impedes cognitive abilities.
The researchers came to the conclusions by comparing the results of 32,000 Chinese men and women who sat the China Family Panel Studies survey in 2010 and 2014. The survey comprises 24 standardised mathematics questions and 34 word-recognition questions, and was sat by people aged 25 years and above from 86 major cities and various rural areas across the country.
The survey’s data set included precise information about where and when the respondents took the tests, enabling the researchers to compare test scores with the official air pollution index in that area.
By comparing the scores from 2014 to those of 2010, the researchers found that the higher the concentration of pollutants, the sharper the declines in the test scores.
They found that both verbal and maths scores decreased with greater air pollution exposure, though verbal scores fell more than maths ones. The study also found that drops in verbal scores were more pronounced among males than females, with the gender gap greater among the less educated.
While physical health has long been thought the most common casualty of air pollution, the study is the first to link poor air quality to cognition and an increase the risk of Alzheimer’s disease, the most common form of dementia.
The findings suggest much higher societal costs than previously attributed to air pollution, especially if it leads to cognitive decline and dementia for the elderly.
“The indirect effect of air pollution on social welfare could be much larger than previously thought,” said Zhang Xiaobo, the study’s lead researcher and an economist at Peking University in Beijing. He is also a senior research fellow at the France-based International Food Policy Research Institute.
Alzheimer’s alone cost US$226 billion of health services and 18 billion labour hours of unpaid caregiving in 2015, according to the Alzheimer’s Association, a non-profit organisation based in Chicago, Illinois.
The results were especially alarming for developing countries where air pollution was ubiquitous, the researchers said. The top 20 most polluted cities are all in developing countries, according to the global air pollution database compiled by the World Health Organisation.
“The research findings on China, the largest developing country with severe air pollution, can also shed light on other developing countries,” Zhang said.