Air Pollution Poses Risk to Thinking Skills in Later Life

Summary: Exposure to air pollution during childhood has a detrimental effect on cognition sixty years later.

Source: University of Edinburgh

A greater exposure to air pollution at the very start of life was associated with a detrimental effect on people’s cognitive skills up to 60 years later, the research found.

Researchers at the University of Edinburgh tested the general intelligence of more than 500 people aged approximately 70 years using a test they had all completed at the age of 11 years.

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 considered lifestyle factors, such as socio-economic status and smoking.

Findings showed exposure to air pollution in childhood had a small but detectable association with worse cognitive change between the ages of 11 and 70 years.

This study shows it is possible to estimate historical air pollution and explore how this relates to cognitive ability throughout life, researchers say.

Dr Tom Russ, Director of the Alzheimer Scotland Dementia Research Centre at the University of Edinburgh, 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.”

This shows a smoke stack
The team used statistical models to analyse the relationship between a person’s exposure to air pollution and their thinking skills in later life. Image is in the public domain

Researchers say until now it has 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 called the EMEP4UK atmospheric chemistry transport model to determine pollution levels — known as 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.

Funding: The study – funded by the Natural Environment Research Council NERC – was carried out in partnership with the UK Centre for Ecology & Hydrology (UKCEH) and the University of Manchester. It was also supported by Age UK (Disconnected Mind project) and Alzheimer Scotland.

About this pollution and cognition research news

Source: University of Edinburgh
Contact: Joanne Morrison – University of Edinburgh
Image: The image is in the public domain

Original Research: Open access.
Life Course Air Pollution Exposure and Cognitive Decline: Modelled Historical Air Pollution Data and the Lothian Birth Cohort 1936” by Tom Russ et al. Journal of Alzheimer’s Disease


Abstract

Life Course Air Pollution Exposure and Cognitive Decline: Modelled Historical Air Pollution Data and the Lothian Birth Cohort 1936

Background:

Air pollution has been consistently linked with dementia and cognitive decline. However, it is unclear whether risk is accumulated through long-term exposure or whether there are sensitive/critical periods. A key barrier to clarifying this relationship is the dearth of historical air pollution data.

Objective:

To demonstrate the feasibility of modelling historical air pollution data and using them in epidemiologicalmodels.

Methods:

Using the EMEP4UK atmospheric chemistry transport model, we modelled historical fine particulate matter (PM2.5) concentrations for the years 1935, 1950, 1970, 1980, and 1990 and combined these with contemporary modelled data from 2001 to estimate life course exposure in 572 participants in the Lothian Birth Cohort 1936 with lifetime residential history recorded. Linear regression and latent growth models were constructed using cognitive ability (IQ) measured by the Moray House Test at the ages of 11, 70, 76, and 79 years to explore the effects of historical air pollution exposure. Covariates included sex, IQ at age 11 years, social class, and smoking.

Results:

Higher air pollution modelled for 1935 (when participants would have been in utero) was associated with worse change in IQ from age 11–70 years (β = –0.006, SE = 0.002, p = 0.03) but not cognitive trajectories from age 70–79 years (p > 0.05). There was no support for other critical/sensitive periods of exposure or an accumulation of risk (all p > 0.05).

Conclusion:

The life course paradigm is essential in understanding cognitive decline and this is the first study to examine life course air pollution exposure in relation to cognitive health.

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