New Research Links Air Pollution And Dementia
Two new studies have added to the growing evidence that exposure to air pollution can harm our brain health and increase the risk of developing dementia. One found that people exposed to higher levels of air pollution in midlife performed worse on memory and thinking tests as they aged. The other, released today, confirms a link between three common types of air pollutants and a higher risk of developing dementia.
Air pollution is caused by tiny particles and gases released into the air from sources like exhausts from vehicles and smoke from fires or power stations. It is now recognised globally as one of 14 modifiable risk factors for developing dementia – meaning it’s something society can take action on to reduce our risk.
Scientists believe air pollution may contribute to dementia by triggering inflammation, damaging brain cells and blood vessels, and harming the heart and lungs over time. But more research is needed to fully understand how air pollution affects the brain.
New research led by experts from the University of Cambridge and published in the journal Lancet Planetary Health, reviewed 51 studies looking at the link between air pollution and dementia risk. The findings are clear: long-term exposure to three types of air pollution – fine-particulate matter (PM2.5), nitrogen dioxide, and soot – is associated with a higher risk of developing dementia.
The researchers found that for every 10 micrograms per cubic meter (μg/m³) increase in PM2.5, a person’s risk of dementia increases by 17%. In 2023, the average roadside level of PM2.5 in central London was 10 μg/m³.
When looking specifically at soot particles, the risk of dementia increased by 13% for every 1 μg/m³ someone was exposed to. For nitrogen dioxide, dementia risk increased by 3% for every 10 μg/m3 of exposure.
A separate study, published last week in the Lancet Healthy Longevity, and part-funded by Alzheimer’s Research UK, adds to the picture. Researchers at King’s College London tracked the brain health of 1,761 people over a 26-year period, comparing their scores on memory and thinking tests – taken between the ages of 43 and 69 – with their exposure to air pollution during midlife. A smaller group also had brain scans.
They found that people exposed to higher levels of air pollution in midlife had lower brain processing speeds and scores in thinking tests, as well as structural changes to their brains, in later life.
The good news is that overall, the UK’s air quality is improving. Since 2015, nitrogen dioxide levels – mostly from vehicle exhausts – have dropped by 35%. And fine particle pollution (like dust, smoke and mould spores) has fallen by around 30%. In 2016, UK cities recorded 136 days where nitrogen dioxide levels were too high. By 2024, that number had dropped to just 40.
Cleaner vehicles, low-emission zones and stricter fuel regulations have all played a role. We also saw a dramatic drop in air pollution levels during the COVID-19 pandemic, when traffic and industrial activity slowed right down.
But there’s still a long way to go. Certain types of pollution – like surface level ozone which forms on hot, sunny days – are now a growing concern for environment experts. And crucially, not everyone is breathing cleaner air. Pollution levels can vary widely depending on where you live, with people living in more deprived areas often exposed to the worst air quality.
Commenting on the two new studies, Dr Isolde Radford, Senior Policy Manager at Alzheimer’s Research UK, has urged the UK Government to step up its action on air pollution.
“While the Government’s new 10-Year Health Plan to fix the NHS and boost the nation’s health acknowledges the health impacts of air pollution, Dr Radford warns that “far more needs to be done to address this invisible threat”.
“At the moment, the Government is working to meet the World Health Organization (WHO) recommended air pollution limits by 2040 – but experts say we can, and should, do better.”
Dr Radford added: “We have the evidence and the means to reach the WHO targets by 2030, and doing so could help prevent thousands more people developing dementia. The Government must act now to introduce stronger, health-based air quality targets that protect our brains as well as our lungs.”
Alzheimer’s Research UK is also calling for a joined-up, cross-government approach to public health – one that brings together departments beyond health, such as transport and the environment, to tackle preventable health conditions like dementia at their root.
