Exposure to air pollution is linked to an increased risk of hospitalization for mental illness, according to the most comprehensive study of its kind.
The study, which involved more than 200,000 people in Scotland, found that in particular, an increase in nitrogen dioxide exposure was linked to a higher number of people being admitted to hospital for behavioral and mental health conditions.
Previously published research on the health effects of long-term exposure to air pollution has tended to emphasize deaths rather than hospitalizations, and physical, rather than mental, ill health, the researchers said.
The study found that air pollution was linked to increased risks of hospitalization for mental health, as well as physical illness.
Stricter environmental restrictions would benefit millions of people and limit 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 reduce the long-term burden on hospitals of people with both physical and mental illnesses relieve.
“Policies and interventions targeting air pollution emissions, such as zero-emission zones or renewable energy incentives in the transportation and energy production sectors, can help alleviate the burden of hospital care in the long term, both locally and globally.”
The analysis of data from Public Health Scotland examined four major pollutants between 2002 and 2017 and the impact of air pollution.
Researchers used individual-level data from the Scottish Longitudinal Study, which represents 5% of the Scottish population and includes demographic information from linked censuses.
A total of 202,237 people aged 17 and older were involved in the study published in the open access journal BMJ Open.
Their health and hospital admissions for cardiovascular, respiratory, infectious diseases, mental health or behavioral disorders were tracked using data from Public Health Scotland.
They were linked to the levels of four pollutants from road traffic and industry: nitrogen dioxide (NO2); sulfur dioxide (SO2); particulate matter diameter of at least 10μm (PM10); and small particles of 2.5 μm or less (PM2.5) per 1 km2 in everyone’s residential zip code.
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Average cumulative exposure to air pollution was strongly associated with higher hospital admissions, for both mental and physical illnesses. Higher cumulative exposure to NO2PM10 and PM2.5 were associated with a higher incidence of hospital admissions regardless of cause.
Ioannis Bakolis, professor of mental health and statistics at King’s College London, who was not involved in the study, said the “large-scale” data had been “appropriately analyzed” and provided further evidence on the link between air pollution and mental health.
Research has previously shown that people who spend their childhood in areas with high levels of air pollution are more likely to develop mental health disorders later in life.
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 will develop bipolar disorder in their lifetime, with similar figures for schizophrenia. It is estimated that about 5% of people in Britain ever have a personality disorder.