UK researchers have been looking at how air pollution contributes to dementia and brain ill-health.
Stroke is the second-leading cause of death globally, accounting for about 11% of deaths. About 50 million people live with dementia, and the figure is expected to rise to about 150 million by 2050.
It is too easy to dismiss this as a natural consequence of an ageing population.
A study has looked at the health of more than 413,000 people taking part in the UK Biobank project. All were between 40 and 69 years old and free of dementia, cancer or stroke at the start of the study. Their health was tracked, focusing on the association between air pollution and the transition from being healthy to having a stroke, dementia or both. Data was also collected on their lifestyles, including smoking, exercise, alcohol consumption and diet, as well as their socioeconomic status.
Over the course of 11 years, 6,484 people had a stroke, 3,813 developed dementia and 376 had a stroke and developed dementia. Having allowed for other risk factors, the researchers found relationships between long-term air pollution exposure and acquiring dementia, as well as developing dementia after a stroke.
Prof Frank Kelly of Imperial College London, who was part of the study team, said: “These new findings help to clarify how air pollution plays an important role in the dynamic transitions of stroke and dementia, even at concentrations below the UK’s current air quality standards.
“The target for particle pollution under the Environment Act is twice the World Health Organization guideline and is set to be achieved by 2040. Not meeting the WHO guideline as soon as possible means that thousands more people are on the path to developing serious illness such as stroke and dementia simply because they are unable to breathe clean air.”
A UK government committee of experts reviewed 69 studies and concluded in 2022 that it was likely air pollution accelerated cognitive decline in elderly people and increased the risk of developing dementia. A further review has also highlighted a growing number of studies on air pollution and the development of more general frailty and cognitive impairment in elderly people.
At the University of Manchester, Prof Gordon McFiggans and his team have built a facility to examine which air pollutants affect our brain health.
At its centre is a clear plastic chamber, or reactor. One corner of the laboratory contains a Volkswagen diesel engine mounted on a trolly. Ducting leads to a trailer outside that contains a modern wood burner and, in a Douglas Adams style twist, another set of ducting connects to a small frying pan. Behind a quartz screen, a set of halogen bulbs, xenon-arc lamps mimic the sun.
Pipework has been installed to allow volunteers to breathe air from inside the chamber itself.
The volunteers are all over 50 and have a family history of dementia or Alzheimer’s disease. McFiggans and his team create standardised mixtures of cooking fumes, cleaning products, diesel exhaust and woodstove smoke to simulate concentrations found in smogs found in many large cities. The volunteers take brain tests before and after breathing the chamber air. Lung cells are also being exposed to the chamber air, and particles are collected for further experiments.
McFiggans said: “We aim to demonstrate to policymakers that the health effects of different sources of pollution can be quantified and can form the basis for a source-oriented guidance, and potentially policy, for harm reduction and avoidance.”
