Air pollution and mental health over the life course

Health

Air pollution and mental health over the life course

There are known links between air pollution and more severe mental illness. Previous NIHR ARC South London research found small rises in exposure to air pollution led to a higher risk of treatment being required by service users with pre-existing mood and psychotic disorders.

Among people with dementia, increased community mental health team usage is associated with higher levels of residential air pollution. If these links are causal, reducing air pollution would reduce health service use in polluted areas, improving the mental health of residents and reducing healthcare costs.

Measures including low emission zones and congestion charges have been implemented in many large cities, and there is evidence that these measures improve safety and physical health. London has had a low emission zone for vehicles since 2008, succeeded by the T-Charge in 2017 and the Ultra Low Emissions Zone (ULEZ) in 2019.

Since 2019, the ULEZ has been in effect 24 hours per day, every day, for the initial inner-city area. The zone has been expanding and now covers all of London, reducing the number of vehicles on the road and measurably decreasing air pollution.

Aims

To quantify the impact of ambient air pollution on population mental health, health service use and mortality and identify potential heath inequities in terms of ethnicity and socio-economic deprivation.

To evaluate the effectiveness and implementation of air pollution reduction related policies on mental health service use, hospital admissions, and mortality within South London.

Methods

The target population of this research are mental health service users with psychiatric or neurological conditions of any age (including those under 18 years old) living within the boroughs of Lambeth, Southwark, Lewisham, and Croydon at any point from four years before the implementation of the ULEZ until the start of the Covid-19 period.

The researchers will obtain and analyse an observational sample of all South London and Maudsley NHS Foundation Trust service users in those boroughs who registered with the service between January 2015 and February 2020.

In the first stage of the research, residents in the ULEZ area will be matched with individuals living in non-ULEZ areas based on age, gender, ethnicity, neighbourhood deprivation, month and year of first contact with secondary mental health services.

In the second stage of the research, the individuals living in the ULEZ area will be compared with those living in non-ULEZ areas, with the researchers looking at changes in mortality, mental health service use and hospital admissions that occurred around the implementation of ULEZ, accounting for seasonal changes and other variables.