Exposure to certain forms of air pollution is linked to an increased risk of developing dementia, according to the most comprehensive study of its kind by Cambridge scientists. The illness affects about 57 million people worldwide, with numbers expected to reach 150 million by 2050.
The study, from the Medical Research Council’s epidemiology unit at the University of Cambridge, reviewed 51 studies with data from over 29 million participants exposed to pollutants for at least a year. It found a positive, statistically significant association between three pollutants and dementia: PM2.5 from vehicle emissions and woodburning stoves; nitrogen dioxide from fossil fuels; and soot from exhaust and burning wood.
For every 10 micrograms per cubic metre of PM2.5, the relative risk of dementia increased by 17%, and by 13% for soot. In 2023, levels of soot and PM2.5 approached or exceeded these thresholds at roadside locations in central London, Birmingham and Glasgow.
Dr Haneen Khreis, senior author, said the study provides “further evidence that long-term exposure to outdoor air pollution is a risk factor for dementia”. She added: “Tackling air pollution can deliver long-term health, social, climate and economic benefits.”
The researchers noted limitations, as most participants were white and from high-income countries. Dr Isolde Radford of Alzheimer’s Research UK called for government action, stating: “Air pollution is one of the major modifiable risk factors for dementia – but it’s not something individuals can solve alone.”
