‘The invisible threat': Air pollution exposure over time raises the risk of dementia, study finds

Yahoo

29-07-2025

Breathing in dirty air regularly could raise your risk of dementia over time, a large new study has found.
The analysis, published in The Lancet Planetary Health journal, is the largest study to date to confirm the connection between air pollution and brain health, though questions remain about the actual mechanism and the time period when people are most at risk.
About 57 million people worldwide have dementia, which occurs when nerve cells' connections in the brain are lost or damaged. Scientists have identified a handful of risk factors, including air pollution, but until now, they haven't known which pollutants were riskiest.
For the new analysis, researchers from the University of Cambridge in the United Kingdom looked at data from 51 reports spanning nearly 30 million people, mostly in high-income countries.
They found strong links between dementia risks and exposure to fine particulate matter from sources such as car emissions, power plants, and dust, as well as nitrogen dioxide from the burning of fuel and soot from things like car exhaust and burning wood.
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These pollutants appear to have stronger ties to vascular dementia, which is caused by reduced blood flow to the brain, than to Alzheimer's disease, the most common form of dementia – but those differences may not be significant.
'Air pollution is not just an environmental issue – it's a serious and growing threat to our brain health,' Dr Isolde Radford, senior policy manager at Alzheimer's Research UK, said in a statement.
Scientists still don't know whether air pollution actually causes dementia or what the biological pathways could be. But they think pollution may cause inflammation and oxidative stress – which can damage cells and DNA – in the brain, both of which have been linked to the onset and progression of dementia.
'The body has no effective defence against the ultrafine particle cocktails we generate outdoors, especially from traffic, and indoors, for example, in heating our homes using stoves,' Barbara Maher, a professor of environmental magnetism at Lancaster University in the UK who was not involved with the study, said in a statement.
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The analysis has some limitations. It is notoriously difficult to track exactly which pollutants a specific person is exposed to over time, how these pollutants interact with each other, and how this affects human health.
This study, along with many others, estimated people's air pollution exposure based on their home address. It also isn't clear when in life this exposure matters most, though researchers believe it may be a period of years or even decades.
'A better approach [to research] is sorely needed,' Dr Tom Russ, a dementia specialist who researches old age psychiatry at the University of Edinburgh, said in a statement.
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'This article answers the question of whether air pollution exposure is associated with dementia better than previous work, but we still need better research to clarify how and why air pollution might be bad for the brain,' added Russ, who was not involved with the study.
Even so, scientists and dementia groups called for governments to enact stricter air quality rules and take other steps to reduce people's exposure to air pollution.
'Far more needs to be done to tackle this invisible threat,' Radford said.