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An observational study published in JAMA Internal Medicine compares particulate air pollution from different emission sources and incident dementia in the US.
Prof Roy Harrison FRS, Professor of Environmental Health, University of Birmingham, said:
“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 indicted by the various studies. The policy position in many countries, including the UK, 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, Reader in Old Age Psychiatry and honorary Consultant Psychiatrist, University of Edinburgh University, said:
“It’s great to see further evidence of the harmful effects of air pollution on the brain. While this paper is better than most, there is still the limitation that air pollution is measured over too short a period of time. Also, exposure to air pollution was estimated from a single residential address – people may have moved and, of course, most people don’t spend all their time at home. 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.”
Prof David Curtis, Honorary Professor, UCL Genetics Institute, University College London (UCL), said:
“As always with this kind of observational study, it is difficult to decide whether the reported association indicates some causal effect of pollution on dementia risk or whether it might have occurred as a result of confounding variables. In any event, the results are only barely statistically significant and indicate that if any causal mechanism is present it only has a modest effect on dementia risk. There is not a very large difference in rates of dementia between those groups with the highest and lowest exposure to pollution. We already know that air pollution is harmful to health and indeed in the UK it is reckoned to cause around 30,000 deaths each year. In this context, whether or not air pollution also has a small effect on dementia risk does not alter the fact that we should be making efforts to improve air quality.”
‘Comparison of Particulate Air Pollution From Different Emission Sources and Incident Dementia in the US’ was published in JAMA Internal Medicine at 16:00 UK time on Monday 14th August.
DOI: 10.1001/jamainternmed.2023.3300
Declared interests
Prof Roy Harrison is a member of the Defra Air Quality Expert Group and the DHSC Committee on the Medical Effects of Air Pollutants. He derives research funding from UKRI and the EU Horizon research programmes.
Dr Tom Russ is a Reader in Old Age Psychiatry at the University of Edinburgh. He is Director of the Alzheimer Scotland Dementia Research Centre at the University of Edinburgh, an honorary Consultant Psychiatrist in NHS Lothian, and Clinical Research Champion of the NHS Research Scotland (NRS) Neuroprogressive & Dementia Network. He is a PI on the Evoke and Evoke+ trials but has no financial involvement with any pharmaceutical company. He researches in the field of air pollution and dementia but has no specific current funding in this area.
Prof David Curtis: “I have no conflict of interest to declare.”