The findings come from a team at King’s College London, who studied the use of mental health services by 5,024 south Londoners living with dementia, over a nine-year period.
The study showed patients living in the most polluted areas were 33 per cent more likely to use such facilities than those living in the least polluted areas.
Researchers believe cutting pollution in the capital could reduce the use of mental health services by dementia patients by as much as 13 per cent.
They added that the expansion of ultra low emission zones (ulez) “could potentially improve functioning and disease trajectories for people with dementia”.
More than half had Alzheimer’s disease (54 per cent), 26.5 per cent had unspecified types of dementia, and 20 per cent had vascular dementia. The latter is caused by issues with the supply of blood to the brain and can be prompted by high blood pressure, stroke or heart problems.
The study, published in medical journal BMJ Mental Health, measured their brain function and health and social functioning at three points in time – up to 12 months after diagnosis, up to five years after diagnosis, and up to nine years after diagnosis.
Researchers then looked at estimates for two major air pollutants – nitrogen dioxide (NO2) and particulate matter – in the areas around the patients’ homes during the same timeframe.
In the first year, higher exposure to both air pollutants was associated with an increase in use of community mental health services.
The researchers said: “Based on the evidence presented, we contend that air pollution could be considered an important population-level target to reduce mental health service use in people with dementia, particularly for those with vascular dementia.”
Those in areas with higher levels of NO2 were 27 per cent more likely to use community mental health services than those living in areas with the lowest levels, while those exposed to the highest levels of particulate matters were 33 per cent more likely to use them.
Researchers said that while air pollution was not associated with cognitive function based on the scale they used, exposure to NO2 was associated with poorer health and social functioning scores, including the capacity for routine and daily living.
They added that as the study was observational, “no firm conclusions can be drawn about cause and effect”.
But they suggested that if the annual level of exposure to inhalable particulate matter in London was reduced, as recommended by the World Health Organisation (WHO), the number of community mental health service contacts made by patients with dementia could fall by 13 per cent.
“The reduction in air pollution and particularly NO2, through public health interventions such as the expansion of ultra low emission zones, could potentially improve functioning and disease trajectories for people with dementia.
“Reducing pollutant exposure might reduce the use of mental health services in people with dementia, freeing up resources in already considerably stretched psychiatric services.”
The capital’s ulez is due to be expanded into outer London from August 29, under controversial plans drawn up by Mayor of London Sadiq Khan in a bid to cut air pollution.
Dr Susan Mitchell, head of policy at charity Alzheimer’s Research UK, said the Government was “dragging its feet” when it comes to implementing stricter air quality standards, and that changes could be “a decade too late”.
She added: “If this Government is serious about improving lifelong health and reducing the burden on our NHS, it can’t continue to turn a blind eye to air pollution.
“Poor air quality is a significant public health issue, and this new research demonstrates its knock-on effect on already over-stretched health services and the lives of people living with dementia.
“As well as urgent action to bring levels down, there is a pressing need to find out more about exactly how air pollution affects dementia risk. This evidence will allow Government and policymakers to develop policies that can reduce the impact of air pollution exposure on people at risk of developing dementia, and those living with the condition.”
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