Air pollution tied to increased dementia risk global study warns
Long-term exposure to air pollution may significantly raise the risk of developing dementia, according to a major new study involving nearly 29 million people.
Published in The Lancet Planetary Health, the research was led by scientists at the University of Cambridge’s MRC Epidemiology Unit. It reviewed 51 studies from across North America, Europe, Asia, and Australia to better understand the relationship between air pollutants and cognitive decline.
The study found strong evidence linking three common pollutants, PM2.5, nitrogen dioxide (NO₂), and soot (black carbon), with an increased risk of dementia, including Alzheimer’s disease and vascular dementia.
Average roadside PM2.5 levels in Central London in 2023 were around 10 μg/m³, while NO₂ levels were approximately 33 μg/m³.
Some pollutants may reach the brain directly via the bloodstream or through the olfactory nerve, while others may cause indirect effects through the cardiovascular and respiratory systems.
The majority of participants in the analysed studies were white and from high-income countries. However, the researchers noted that marginalised and low-income communities, who are more likely to be exposed to air pollution, are underrepresented in research.
“Efforts to reduce exposure to these key pollutants are likely to help reduce the burden of dementia on society,” said co-author Clare Rogowski.
Public health implications
Globally, over 57 million people are estimated to be living with dementia. That number is projected to rise to 152.8 million by 2050, according to the World Health Organization.
While other factors such as age, genetics, diet, and lifestyle play significant roles in dementia risk, researchers argue that environmental policies should be considered part of dementia prevention strategies.
The study was funded by the European Research Council and the European Union’s Horizon Europe Framework Programme.
Published in The Lancet Planetary Health, the research was led by scientists at the University of Cambridge’s MRC Epidemiology Unit. It reviewed 51 studies from across North America, Europe, Asia, and Australia to better understand the relationship between air pollutants and cognitive decline.
The study found strong evidence linking three common pollutants, PM2.5, nitrogen dioxide (NO₂), and soot (black carbon), with an increased risk of dementia, including Alzheimer’s disease and vascular dementia.
Key findings
- For every 10 micrograms per cubic metre (μg/m³) increase in PM2.5, the risk of developing dementia rose by 17 percent.
- A 10 μg/m³ increase in NO₂ was linked to a 3 percent rise in dementia risk.
- Each 1 μg/m³ increase in soot was associated with a 13 percent higher risk.
Average roadside PM2.5 levels in Central London in 2023 were around 10 μg/m³, while NO₂ levels were approximately 33 μg/m³.
Possible biological mechanisms
Researchers believe air pollution may contribute to dementia through oxidative stress and inflammation, processes that damage brain cells and are known to play a role in the development of neurodegenerative conditions.Some pollutants may reach the brain directly via the bloodstream or through the olfactory nerve, while others may cause indirect effects through the cardiovascular and respiratory systems.
Unequal exposure
The majority of participants in the analysed studies were white and from high-income countries. However, the researchers noted that marginalised and low-income communities, who are more likely to be exposed to air pollution, are underrepresented in research.
“Efforts to reduce exposure to these key pollutants are likely to help reduce the burden of dementia on society,” said co-author Clare Rogowski.
Public health implications
Globally, over 57 million people are estimated to be living with dementia. That number is projected to rise to 152.8 million by 2050, according to the World Health Organization.
While other factors such as age, genetics, diet, and lifestyle play significant roles in dementia risk, researchers argue that environmental policies should be considered part of dementia prevention strategies.
The study was funded by the European Research Council and the European Union’s Horizon Europe Framework Programme.
