A huge new study has found a link between air pollution and dementia. Led by the University of London and King’s College London, the team stress that the causes of dementia, including Alzheimer’s disease, are still ambiguous and “may be multifactorial.”
Nevertheless, their work should encourage further research, especially as the future global burden of dementia will be substantial.
Published in BMJ Open, the study looked at 130,978 adults aged 50-79, who, prior to 2005, had no history of dementia. Their addresses were used to approximate concentrations of nitrogen dioxide and ozone. These are common components of various air pollution sources, from traffic to fossil fuel-fired power plants, and are linked to a range of negative health outcomes.
Of those adults, 1.7 percent were diagnosed with dementia; 39 percent developed Alzheimer’s and 29 percent got the vascular variety. Adjusting for age, sex, ethnicity, smoking, and body mass index, the researchers found that adults living in areas with the highest degrees of nitrogen dioxide had a 40 percent higher risk of dementia than those in low-pollution areas.
That’s increased risk, not absolute, so here’s another way of looking at it: The paper suggests that if all their subjects were living in the low-pollution zones, 7 percent of the total number of current dementia cases in the UK could still be attributable to air pollution.
Dementia is the leading cause of death in England and Wales. The World Health Organization (WHO), noting that 10 million new cases are diagnosed worldwide each year, has made it a public health priority. It currently has no cure.
As a retrospective cohort study – in which correlations are described, but cause-and-effect mechanisms can’t be established – the interpretation of the data must be taken cautiously, something the authors themselves acknowledge. This paper doesn’t stand in isolation, though: the link between air pollution and dementia, along with cognitive problems, has been looked into several times, and worrying trends are emerging.