Healthcare (Commonwealth Union) – A review of research covering data from nearly 30 million people has underscored the connection between air pollution — including emissions from vehicle exhaust — and a heightened risk of developing dementia.
Conditions such as Alzheimer’s disease currently affect over 57.4 million individuals worldwide, and that figure is projected to almost triple to 152.8 million by the year 2050. Its impact on patients, their families, caregivers, and society completely are a large endeavor.
Despite the fact that some evidence pointes in the direction that dementia rates in Europe and North America may be going down — offering hope that the risk could be lessened at a population level — the outlook in other regions is still far less optimistic.
Recent studies marked air pollution as a contributing factor to dementia, with a variety of studies implicating multiple pollutants. Still, the strength of the proof and the ability to claim a direct cause have differed widely.
In recent research published in The Lancet Planetary Health, researchers from the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge carried out a systematic review and meta-analysis of available studies to probe this link in detail. This method enabled them to combine research that, when considered separately, might lack sufficient weight — or even produce conflicting results — into more reliable, overarching conclusions.
Altogether, the team analyzed 51 studies covering data from over 29 million people who had been exposed to air pollution for a minimum of one year, predominantly in high-income nations.
The findings showed a clear, statistically significant connection in dementia risk and three types of air pollutants:
The evaluation estimated that with every 10 micrograms per cubic meter (μg/m³) increase in PM2.5 exposure, an individual’s relative risk of developing dementia was elevated by 17%. For comparison, roadside PM2.5 levels in Central London in 2023 averaged around 10 μg/m³.
For every 10 μg/m³ increase in nitrogen dioxide (NO₂), the likelihood of developing dementia rose by 3%. In 2023, the average roadside NO₂ level recorded in Central London was 33 μg/m³.
When it came to fine particulate matter (PM2.5) in the form of soot, each 1 μg/m³ increase was linked to a 13% higher risk. That same year, annual average soot concentrations measured at roadside sites were 0.93 μg/m³ in London, 1.51 μg/m³ in Birmingham, and 0.65 μg/m³ in Glasgow.
Lead researcher Dr. Haneen Khreis of the MRC Epidemiology Unit indicated that epidemiological studies are vital in helping us determine whether air pollution raises dementia risk—and to what extent. She pointed out that their findings add to the growing body of evidence that long-term exposure to outdoor air pollution contributes to the development of dementia in adults who were previously healthy.
“Tackling air pollution can deliver long-term health, social, climate, and economic benefits. It can reduce the immense burden on patients, families, and caregivers, while easing pressure on overstretched healthcare systems.”
Scientists have suggested several pathways by which air pollution might contribute to dementia, most notably through brain inflammation and oxidative stress. Both of these factors are widely recognized as key drivers in the development and progression of dementia. Pollution is believed to set off these harmful processes either by entering the brain directly or through mechanisms similar to those involved in lung and heart diseases.
Researchers of the study pointed out that since evidence suggests that cutting exposure to pollution brings even greater benefits in lowering early mortality risks for these communities, the authors stress the urgent need for future research to include more diverse ethnic groups as well as populations from low- and middle-income countries.
