New research has found that exposure to air pollution is significantly affecting our memory, causing a loss in memory which could be equivalent to up to ten years of ageing.
Carried out by researchers from the University of Warwick, the new study looked at a nationally-representative sample of 34,000 individuals across 318 geographical areas in England.
The researchers collected information on air quality for each district, including levels of both nitrogen dioxide (NO2) and particulate matter (PM10), which are particles with a diameter of 10 micrometres or smaller. Both are produced by burning fossil fuels from car and other vehicle exhausts, power plants and industrial emissions.
The participants were asked to remember 10 words in a standardised word-recall test and were given a score from zero to ten based on their answers.
The researchers also took into account participants’ age, health, level of education, ethnicity, and family and employment status, which are factors that can impact memory.
The findings showed that memory scores were significantly worse for participants living in parts of England with high levels of NO2 and PM10.
In fact, the researchers estimated that the difference in memory between England’s cleanest areas, found on the west coastline in districts such as Devon and West Somerset, and most-polluted areas, places like Kensington and Islington in London, is equivalent to the loss of memory from 10 extra years of ageing.
“When it comes to remembering a string of words, a 50-year old in polluted Chelsea performs like a 60-year old in Plymouth. We are still not exactly sure how nitrogen dioxide and air particulates act to do this,” commented co-author Professor Andrew Oswald.
The researchers say that although caution is always needed when interpreting a causal relationship, they describe the results as “concerning”, and add that they are consistent with those produced by animal studies, although this is one of the first studies to confirm the results in humans.
“There is a little prior evidence of a negative association between levels of traffic pollution and memory using data on elderly individuals and in children,” said co-author Professor Nattavudh Powdthavee, “but almost all research in human studies on this topic has been based on elementary correlations and not on nationally representative samples of individuals in a country. We have tried to solve these two problems in our study.”