Air Pollution linked to Cognitive decline, Study Finds

In a new study, Researchers in China have found that Chronic exposure to air pollution could be linked to a decline in cognitive performance and that the impact increases with age. The paper has been published in Proceedings of the National Academy of Sciences, PNAS.

The researchers conducted math and verbal tests over the course of multiple years on more than 25,000 people in 162 Chinese counties. They matched those results with pollution conditions at the time of each test and found the results.

The study was based on measurements of sulphur dioxide, nitrogen dioxide and particulates smaller than 10 micrometres in diameter where participants lived. Carbon monoxide, ozone and larger particulates were not included in the study.

Most of the population in developing countries live in places with unsafe air and therefore damage on the ageing brain by air pollution likely imposes substantial health and economic costs, considering that cognitive functioning is critical for the elderly for both running daily errands and making high-stakes decisions.

The findings underscore the need for China to clean up the air, says study co-author Xi Chen, a professor of health policy and economics at the Yale School of Public Health.

"If the air pollution improves from China's level to the American EPA standard level, that means that would improve everyone's education by around one year," Chen said, referring to an annual EPA standard measurement for particulate matter that was used until 2006.

The researchers tested the same subjects in 2010 and 2014, and the math and verbal tests were meant to show "different dimensions, representative of the functioning of the brain," Chen said. The data allowed the researchers to compare the effect of pollution across ages, from children to the elderly.

"We can say that the bigger impact is toward the older adults," Chen added.

The scientists evaluated both short-term and cumulative effects of air pollution on cognitive performance. t was found that pollution's impact on verbal test performance became worse as people aged, particularly among men and people with less education.

People with lower education levels are likely to experience more harm, Chen says, because they work outside more often and are exposed to higher levels of pollution.

He says exposure to pollution could make elderly people less effective in making major financial and medical decisions.

Could the link between cognitive decline and pollution be caused by another factor? Chen says the study tries to overcome that issue by testing the same people over time.

It's not clear precisely how pollution impacts cognitive decline, though Chen suggests that pollution may have a negative effect on the brain's white matter, which could vary between men and women. As NPR has reported, "the brain's white matter coordinates communication among brain regions."

Air pollution around the world - the facts

• About seven million people die every year from exposure to polluted air


• Air pollution caused 4.2 million deaths globally in 2016


• 91% of the world's population lives in places where air quality exceeds WHO guideline limits


• 14 Indian cities are among the world's 20 most polluted, with the northern city of Kanpur topping the list


• Nine out of 10 people in the world breathe polluted air