Air pollution in childhood linked to decline in cognitive ability, research suggests

The impacts of air pollution are diverse, with research in recent years indicating respiratory issues are not the only adverse effects small particulate matter and airborne toxins can have on humans.

Air pollution has been linked to depression, dementia, sight loss, declining mental health, miscarriages and smaller babies in pregnant women, bladder cancer, brittle bones, fertility problems, damaged skin, as well as a range of pulmonary and cardiovascular conditions, including strokes, heart disease, lung cancer and acute respiratory infections. It has been suggested that air pollution damages every organ and practically every cell in the human body.

The problem is also alarmingly prevalent: Nine out of 10 people live in areas where pollutants in the air exceed WHO guideline limits, and air pollution is estimated to kill around seven million people around the world every year, though scientists have described this as “the tip of the iceberg”.

New research by a team at the University of Edinburgh now suggests exposure to air pollution in childhood is linked to a decline in cognitive ability in later life.

Growing up in areas with toxic air was associated with a detrimental effect on people’s thinking skills up to 60 years later, the research found.

The scientists tested the general intelligence of more than 500 people aged who were all around 70 years old, using a test they had all completed back when they were 11 years old.

The participants then repeated the same test at the ages of 76 and 79 years.

A record of where each person had lived throughout their life was used to estimate the level of air pollution they had experienced in their early years.

The team used statistical models to analyse the relationship between a person’s exposure to air pollution and their thinking skills in later life. They also took into account lifestyle factors, such as socio-economic status and smoking.

The results of the study suggested heightened exposure to air pollution in childhood had a small but detectable association with worse cognitive change between the ages of 11 and 70 years.

Dr Tom Russ, director of the Alzheimer Scotland Dementia Research Centre, said: “For the first time we have shown the effect that exposure to air pollution very early in life could have on the brain many decades later.

“This is the first step towards understanding the harmful effects of air pollution on the brain and could help reduce the risk of dementia for future generations.”

The researchers said their study indicates it is possible to estimate historical air pollution and explore how this relates to cognitive ability throughout life.

Until now it had not been possible to explore the impact of early exposure to air pollution on thinking skills in later life because of a lack of data on air pollution levels before the 1990s when routine monitoring began.

For this study researchers used a model to estimate historical fine particulate matter (PM2.5) concentrations for the years 1935, 1950, 1970, 1980, and 1990. They combined these historical findings with contemporary modelled data from 2001 to estimate life course exposure.

The participants were part of the Lothian Birth Cohort 1936 study, a group of individuals who were born in 1936 and took part in the Scottish Mental Survey of 1947.

Since 1999, researchers have been working with the Lothian Birth Cohorts to chart how a person’s thinking power changes over their lifetime.

The study is published in the Journal of Alzheimer's Disease and in the Handbook on Air Pollution.