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.  

Here we explore what the latest studies reveal about the impact of air pollution on brain health, and what we can do to reduce our risk and clean up the air we breathe.

 

What does the new research tell us?

New research released today, 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.    

 

Is our air quality getting better or worse?

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.  

 

What needs to happen to tackle air pollution?

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.

 

What else is Alzheimer’s Research UK doing?

Alzheimer’s Research UK is a member of the Healthy Air Coalition – a group of health and environmental organisations campaigning to cut air pollution. As part of the Coalition we are campaigning for the Government to meet its manifesto pledge to bring in a new Clean Air Act, and for the UK speed up action to meet WHO targets.

We’re also backing vital research from Dr Jake Brooks at the University of Warwick to uncover how polluted air may damage the brain and contribute to diseases like Alzheimer’s – helping to drive more targeted action in the future.

 

What can we do to protect our brains from air pollution? 

While we can’t tackle levels of air pollution on our own, there are some practical steps we can all try to take to reduce how much pollution we are exposed to.

Try to avoid spending long periods near busy roads or areas with heavy traffic, especially during rush hour, and walk or cycle through parks and less polluted areas if you can.

If you use gas or wood-burning stoves, make sure you have safe and effective ventilation. And using greener transport options if you can – from walking and cycling, to taking the bus, train or carpooling – can have huge benefits for our individual health, as well as reducing overall pollution in our communities.   

 

Head to Think Brain Health to get more tips for looking after your brain health.