- American researchers examined more than 900 people aged 60 and over
- Experts believe that air pollution could increase the risk of 'silent strokes'
- Microscopic particles in pollution are thought to kill 29,000 people a year
- The risk of having a silent stroke can be raised by more than 40 per cent
Living near congested roads with high levels of air pollution can cause ‘silent strokes’ which increase the risk of dementia, scientists have warned.
Exposure to small, sooty particles, mostly caused by traffic fumes and factory emissions, alters the structure of the brain, they said.
The microscopic particles have previously been shown to cause lung damage and harmful changes in blood vessels and clotting, and are thought to contribute to the deaths of 29,000 people every year in Britain.
Living near a congested road can increase the chance of developing dementia, research has found
Researchers examined the brains of more than 900 people aged more than 60 and assessed the pollution risk
US researchers found evidence that living near congested roads or polluted areas can lead to ‘silent strokes’ which in turn cause shrinkage of the brain and other damage.
Silent strokes, which arise from blockages in blood vessels supplying the brain, do not have any outward symptoms and the victim is usually unaware of them.
Sudha Seshadri, a professor of neurology at Boston University School of Medicine, said: ‘This is concerning, since we know that silent strokes increase the risk of overt strokes and of developing dementia, walking problems and depression.
‘We now plan to look more at the impact of air pollution over a longer period, its effect on brain shrinkage over time, and other risks including stroke and dementia.’
The study, by Beth Israel Deaconess Medical Center and Boston University School of Medicine, involved more than 900 people aged 60 and over who did not have dementia or a history of strokes.
It recorded how far participants lived from major roads and used satellite imagery to assess their exposure to the fine particulate matter known as PM2.5. This is made up of small particles measuring just 2.5 micrometres, or 30 times smaller than the thickness of a human hair. These particles are generated from a variety of sources, including power plants, factories, trucks and cars and the burning of wood.
They can travel deeply into the lungs and have been associated with increased numbers of hospital admissions for heart attacks and strokes.
The study participants’ brain matter was measured using MRI scans. The researchers found that increases in PM2.5 in towns and cities was linked with a 46 per cent higher risk of silent strokes.
The research was published in a report in the journal Stroke.
Researcher Elissa Wilker, of the Cardiovascular Epidemiology Research Unit at Beth Israel Deaconess Medical Center, said: ‘This is one of the first studies to look at the relationship between ambient air pollution and brain structure.
‘Our findings suggest that air pollution is associated with insidious effects, even in dementia and stroke-free individuals.
‘The mechanisms remain unclear, but inflammation resulting from the deposit of fine particles in the lungs is likely important.’
The study will add to mounting pressure on the Government, which faces a judgment at the Supreme Court next week over its failure to meet EU legal limits for air pollution. Sixteen cities – including London, Manchester, Glasgow, Sheffield and Birmingham – have failed to hit air quality targets.