Fine particulate matter (PM2.5) air pollution may increase older people’s risk of developing dementia — particularly in the case of pollution from agriculture and wildfires.
This is the conclusion of a team of researchers from the US who analyzed health data on nearly 30,000 people collected biannually over the course of around a decade.
The team found that 15 percent of the subjects went on to experience dementia during the study — with those exposed more to PM2.5 in their neighborhood being slightly more likely to develop the condition.
The study was observational, meaning that it has only revealed a correlation between fine air pollution and dementia risk, rather than a causal link.
However, this adds to mounting evidence in support of such a connection, with the researchers concluding that more work is needed to explore how this might be addressed.
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The study was undertaken by epidemiologist Dr Boya Zhang of the University of Michigan School of Public Health and her colleagues.
The researchers wrote: “These findings support the hypothesis that airborne particulate matter pollution is associated with the likelihood of developing dementia.”
Past studies, they noted, have suggested that the smallest airborne pollutant particles, “often coated with neurotoxic chemicals” are capable of entering the brain via either the olfactory bulb of the blood–brain barrier.
The team added: “Selective interventions to reduce pollution exposure may decrease the life-long risk of dementia; however, more research is needed to confirm these relationships.”
Professor Roy Harrison — an expert in environmental health from the University of Birmingham who was not involved in the present study — commented: “This paper provides useful support for the earlier findings in a number of studies that exposure to fine particles (PM2.5) has adverse effects on cognitive function and can accelerate the onset of dementia.
“The apparently larger association with particles arising from agriculture and wildfires is less convincing, with results only just achieving statistical significance.
“There are important policy implications of identifying those sources or chemical components of particles most associated with the adverse effects.
“However, the scientific work to date does not provide a coherent picture, with many particle sources and components indicated by the various studies.
“The policy position in many countries […] is to regard all PM2.5 particles, irrespective of source, as being of equal toxicity per unit mass, and this paper does not justify a reconsideration of that view.”
Dr Tom Russ of the University of Edinburgh added: “Dementia develops over several decades before the symptoms occur and air pollution could affect the brain at any time.
“This study only looks back ten years, which may not be long enough. We need more research looking at the effects of air pollution on the brain across the whole life course.”
The full findings of the study were published in the journal JAMA Internal Medicine.
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