Researchers in the UK have added more evidence into the relationship between air pollution and cognitive decline, particularly its contribution to dementia and other brain-related illnesses.

Globally, stroke ranks as the second-leading cause of death, responsible for approximately 11% of all fatalities. Meanwhile, the prevalence of dementia affects around 50 million individuals, with projections indicating a surge to about 150 million by 2050.

While aging is often cited as a primary factor, dismissing these trends solely as a consequence of an aging population oversimplifies the complex interplay of environmental factors.

A comprehensive study examined the health trajectories of over 413,000 participants enrolled in the UK Biobank project, aged between 40 and 69 and initially free from dementia, cancer, or stroke. Over an 11-year period, the researchers meticulously tracked their health, scrutinising the correlation between air pollution exposure and the onset of stroke, dementia, or both. Data encompassed various lifestyle factors such as smoking, exercise, diet, alcohol consumption, and socioeconomic status.

Findings revealed alarming statistics: during the study period, 6,484 individuals suffered strokes, 3,813 developed dementia, and 376 experienced both. Even after adjusting for confounding risk factors, the researchers identified significant associations between prolonged exposure to air pollution and the incidence of dementia, as well as the development of dementia post-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.”

In 2022, a UK government panel of experts scrutinised 69 studies, concluding that air pollution likely hastens cognitive decline in the elderly and elevates the risk of dementia. Furthermore, a subsequent review underscored an expanding body of evidence linking air pollution not only to dementia but also to generalised frailty and cognitive impairment in the elderly.

At the University of Manchester, Professor Gordon McFiggans and his team have pioneered a cutting-edge facility to explore the impact of air pollutants on brain health. Central to their research is a state-of-the-art chamber, housing a Volkswagen diesel engine, a modern wood burner, and even a frying pan to replicate urban smog conditions.

Within this controlled environment, volunteers, primarily over 50 with a family history of dementia or Alzheimer’s, breathe standardised mixtures of pollutants, ranging from cooking fumes to diesel exhaust. Their cognitive functions are evaluated before and after exposure, while lung cells undergo parallel assessments. This innovative approach aims to elucidate the mechanisms underlying air pollution’s detrimental effects on brain health and inform strategies to mitigate its impact.

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.”