NEW YORK, April 10 ― New US research has found that living in an area where this is a high level of pollution could affect an individual's thinking and memory skills.

Carried out by researchers at Brown University, the new study looked at two groups of people living in the Northern Manhattan area of New York City, including one group of 5,330 adults with an average age of 75, and another group of 1,093 people with an average age of 70.

All of the participants were tested on their cognitive skills at the beginning of the study, which included assessing memory, language skills and executive function ― which refers to thinking skills that help with impulse control, organizing, planning and completing tasks.

Their exposure to three types of air pollution were also calculated using their home addresses. These pollutants included nitrogen dioxide (NO2), PM10, which are particles of liquids or solids suspended in the air with a diameter of 10 micrometers or smaller, and PM2.5, which are particles that are less than 2.5 micrometers or smaller.

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The larger group of participants was then followed for an average of seven years and underwent six rounds of follow-up tests, while the smaller group was followed for five years with one follow-up test.

The findings, published online in Neurology, the medical journal of the American Academy of Neurology, showed that the larger group of participants were exposed to a yearly average of 32 parts per billion of nitrogen dioxide, 13 micrograms per cubic meter (μg/m3) of PM2.5 and 21 μg/m3 of PM10.

To put that into context, the US Environmental Protection Agency (EPA) considers up to 53 parts per billion to be a safe level of yearly average exposure to nitrogen dioxide, up to 12 μg/m3 for PM2.5, and up to 50 μg/m3 for PM10.

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In addition, the researchers found that in this larger group, the participants who were exposed to higher levels of air pollution scored lower on the cognitive tests completed at the start of the study and showed a quicker cognitive decline during the follow-up. For example, exposure to nitrogen dioxide was linked to an increased rate of cognitive decline comparable to one year of aging, with similar results found for exposure to PM2.5 and PM10 and across the functional cognitive domains looked at in the study.

However, the same associations between cognitive function and exposure to air pollution were not found in the other group. The researchers say this could be due to the second group being smaller and only undergoing one follow-up test.

“As people live longer lives and the aging population grows, age-related cognitive decline is a growing public health concern with profound social, economic and health effects, so finding ways to reduce the risk is important,” said study author Erin R Kulick, PhD, MPH. “Air pollution can affect large populations of people because it has known cardiovascular risks, and previous research has found that it may also contribute to cognitive decline. However, the results of our research were mixed.”

“While the levels were in the range considered safe by the EPA, it's possible that these results reflect higher levels from an earlier point in time. It also raises the question of whether the federal levels are low enough to protect people's health,” said Kulick. ― AFP-Relaxnews