Researchers at the University of Cambridge have confirmed a significant link between air pollution and the risk of dementia, urging global policy changes to address this critical public health issue.
Long-term exposure to outdoor air pollution, including common pollutants from car exhausts, power plants and industrial emissions, significantly increases the risk of dementia. This is according to a large-scale analysis published today in The Lancet Planetary Health by a team from the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge.
This meta-analysis, one of the most comprehensive of its kind, synthesized data from 51 studies involving nearly 30 million individuals. Primary findings identified three pollutants — PM2.5 (particulate matter with a diameter of 2.5 microns or less), nitrogen dioxide (NO2) and soot — as significantly associated with increased dementia risk.
“Epidemiological evidence plays a crucial role in allowing us to determine whether or not air pollution increases the risk of dementia and by how much,” senior author Haneen Khreis, from the MRC Epidemiology Unit, said in a news release. “Our work provides further evidence to support the observation that long-term exposure to outdoor air pollution is a risk factor for the onset of dementia in previously healthy adults.”
The study found that for every 10 micrograms per cubic meter (μg/m³) increase in PM2.5, the relative risk of developing dementia rose by 17%. For the same increase in NO22 levels, risk increased by 3%, and for each 1 μg/m³ of soot, the risk went up by 13%.
The average levels of these pollutants in urban areas like Central London underscore the urgency. In 2023, PM2.5 levels averaged 10 μg/m³, while NO2 levels were 33 μg/m³.
While dementia rates are declining in parts of Europe and North America due to better health care and preventive measures, the global burden is expected to rise sharply — from 57.4 million cases today to 152.8 million by 2050. Air pollution thus represents a crucial modifiable risk factor.
“Tackling air pollution can deliver long-term health, social, climate and economic benefits,” Khreis added. “It can reduce the immense burden on patients, families and caregivers, while easing pressure on overstretched healthcare systems.”
The study primarily involved participants from high-income countries, highlighting a gap in research among marginalized communities that often experience higher exposure to pollutants. Given that mitigation efforts can have significant benefits, the authors urge for inclusivity in future research and interventions.
“Efforts to reduce exposure to these key pollutants are likely to help reduce the burden of dementia on society,” added joint first author Clare Rogowskir from the MRS Epidemiology Unit. “Stricter limits for several pollutants are likely to be necessary targeting major contributors such as the transport and industry sectors.”
In addition to Alzheimer’s disease, the analysis revealed a stronger effect of pollutants on vascular dementia, a type characterized by reduced blood flow to the brain, affecting around 180,000 people in the UK. However, due to the limited number of specific studies, this distinction wasn’t classified as statistically significant.
“These findings underscore the need for an interdisciplinary approach to dementia prevention,” added joint first author Christiaan Bredell from the University of Cambridge and North West Anglia NHS Foundation Trust. “Preventing dementia is not just the responsibility of healthcare: urban planning, transport policy and environmental regulation all have a significant role to play.”
The research offers compelling evidence supporting urgent policy interventions at local, national and international levels.
Source: University of Cambridge