Exposure to air pollution is linked to an increased risk of hospital admission for mental illness, according to the most comprehensive study of its kind.
The research, involving more than 200,000 people in Scotland, found an increase in exposure to nitrogen dioxide in particular was associated with a higher number of people being admitted to hospital for behaviour disorders and mental illnesses.
Previously published research on the health effects of long-term exposure to ambient air pollution has tended to emphasise deaths rather than hospital admissions, and physical, rather than mental, ill health, the researchers said.
The study found that air pollution was linked to increased risks of hospital admission for mental health, as well as physical illness.
Stricter environmental restrictions would benefit millions of people and curb the impact on secondary care, the researchers said.
Dr Mary Abed Al Ahad of the University of St Andrews, who led the study, said policies to tackle air pollution and a shift to renewable energy could help ease the burden on hospitals of people with both physical and mental illnesses in the long term.
“Policies and interventions targeting air pollution emissions such as zero-emission zones or incentives for renewable energy in transportation and energy production sectors could help ease the hospital-care burden in the long term both locally and globally.”
The analysis of data tracked from Public Health Scotland examined four key pollutants between 2002 and 2017 and the impact of ambient air pollution.
Researchers drew on individual level data from the Scottish Longitudinal Study, which represents 5% of the Scottish population and includes demographic information from linked censuses.
In all, 202,237 people aged 17 and above were included in the research, which was published in the open access journal BMJ Open.
Their health and hospital admissions for cardiovascular, respiratory, infectious diseases, mental illnesses or behaviour disorders were tracked from Public Health Scotland data.
They were linked to levels of four pollutants from road traffic and industry: nitrogen dioxide (NO2); sulphur dioxide (SO2); particulate matter diameter of at least 10μm (PM10); and small particulate matter of 2.5μm or less (PM2.5) per 1km2 in each person’s residential postcode.
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Average cumulative exposure to air pollution was strongly associated with higher rates of hospital admissions, both for mental and physical illnesses. Higher cumulative exposure to NO2, PM10, and PM2.5 was associated with a higher incidence of hospital admissions for all causes.
Ioannis Bakolis, a professor of public mental health and statistics at King’s College London who was not involved with the study, said the “large-scale” data was “appropriately analysed” and provided further evidence on the link between air pollution and mental health.
Research has previously shown how people who spend their childhood in areas with high levels of air pollution may be more likely to later develop mental disorders.
But a study by researchers in the US and Denmark has suggested a link between air pollution and an increased risk of mental health problems, including bipolar disorder, schizophrenia and personality disorders.
Between 1% and 2% of the UK population have bipolar disorder in their lifetime, with similar figures for schizophrenia. It is estimated that about 5% of people in the UK have a personality disorder at any one time.
