Air pollution link to dementia severity

Reducing air pollution through public health programmes, such as ultra-low emission zones, could help to improve the health of people with dementia, a new study says today.

A large, long-term observational study by a team at King’s College London says exposure to higher levels of air pollution is linked to greater use of community mental health services by people with dementia.

Although air pollution has already been linked to increased health service use by people with dementia, but the studies have focused on hospital services, rather than community services.

The study looked back at community mental health service use over nine years by 5,024 people aged 65 and over living in four boroughs of South London with initial dementia diagnosis between 2008 and 2012.

Writing in today’s BMJ Mental Health, the authors say: “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.”

In the study, 54% (2718) had been diagnosed with Alzheimer’s disease, 20% (1022) had vascular dementia, and 26.5% (1330) had other or unspecified dementia.

Quarterly published estimates of two major air pollutants – nitrogen dioxide (NO2) and particulate matter (PM2.5 and PM10) – covering the area around participants’ homes were linked with their anonymised mental health records for the period 2008-12.

They found exposure to all air pollutants was highest in people with vascular dementia and lowest in those with Alzheimer’s disease.

The team divided the monitoring period into three time points: up to 12 months; up to five years; and up to nine years after diagnosis.

In the first year of monitoring, higher exposure to all air pollutants was associated with an increase in the use of community mental health services by people with dementia, with the higher the level of exposure, the greater the use of these services, particularly for exposure to NO2. This was especially noticeable among those with vascular dementia.

Those living in areas with the highest level of exposure were 27% more likely to use these services, while individuals exposed to the highest levels of PM2.5 were 33% more likely to use mental health services.

The associations between PM2.5 and more frequent mental health service use remained five and nine years later for people with Alzheimer’s disease and vascular dementia but were most noticeable for those with vascular dementia.

The researchers used the Mini Mental State Exam (MMSE) to measure brain function and the Health of the Nation Outcomes Scale (HoNOS65+) was used to measure physical health and social activity.

At all time points, exposure to NO2 was associated with higher HoNOS65+ scores, indicating poorer health and social functioning, but not poorer cognition. There were similar findings for particulate matter.

While air pollution was not associated with brain function as measured by MMSE results over the study period, exposure to NO2 was associated with higher HoNOS65+ scores at all time points, indicating poorer health and social functioning. The findings were similar for PM2.5.

Researchers acknowledge study limitations, including being unable to assess the impact of early life exposure to pollutants or fluctuations in exposure over the nine years, or changes in exposure due to residential mobility or time away from home.

Nevertheless, they estimate if the annual PM2.5 exposure in London (11.6 µg/m3 in 2019) fell to 5 µg/m3, as recommended by the World Health Organization (WHO), there could be a 13% reduction in the number of community mental health service contacts by people with dementia.

Reducing annual levels of NO2 (39 µg/m3 in 2019) to the recommended limit of 10 µg/m3 could reduce annual mental health service contacts by 38%.

They write: “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.”

Ronaldson A, Stewart R, Mueller C et al. Associations between air pollution and mental health service use in dementia: a retrospective cohort study. BMJ Mental Health 8 August 2023. doi 10.1136/bmjment-2023-300762


, , , , ,

Leave a Reply

Your email address will not be published. Required fields are marked *



Monthly Posts

Our Clients

Practice Index