Exposure to air pollution during childhood and risk of developing schizophrenia: a national cohort study.

BACKGROUND

Ambient air pollution affects neurological function, but its association with schizophrenia risk is unclear. We investigated exposure to nitrogen oxides (NO) as a whole and nitrogen dioxide (NO) specifically, as well as PM, and PM, during childhood and subsequent schizophrenia risk.

METHODS

People born in Denmark from 1980 to 1984 (N=230 844), who were residing in the country on their tenth birthday, and who had two Danish-born parents were followed-up from their tenth birthday until schizophrenia diagnosis or Dec 31, 2016. Mean daily exposure to each pollutant (NO, NO, PM, and PM) at all of an individual's residential addresses from birth to their tenth birthday was modelled. Incidence rate ratios, cumulative incidence, and population attributable risks were calculated using survival analysis techniques.

FINDINGS

We analysed data between Aug 1, 2018, and Nov 15, 2019. Of 230 844 individuals included, 2189 cohort members were diagnosed with schizophrenia during follow-up. Higher concentrations of residential NO and NO exposure during childhood were associated with subsequent elevated schizophrenia risk. People exposed to daily mean concentrations of more than 26·5 μg/m NO had a 1·62 (95% CI 1·41-1·87) times increased risk compared with people exposed to a mean daily concentration of less than 14·5 μg/m. The absolute risks of developing schizophrenia by the age of 37 years when exposed to daily mean concentrations of more than 26·5 μg/m NO between birth and 10 years were 1·45% (95% CI 1·30-1·62%) for men and 1·03% (0·90-1·17) for women, whereas when exposed to a mean daily concentration of less than 14·5 μg/m, the risk was 0·80% (95% CI 0·69-0·92%) for men and 0·67% (0·57-0·79) for women. Associations between exposure to PM or PM and schizophrenia risk were less consistent.

INTERPRETATION

If the association between air pollution and schizophrenia is causal, reducing ambient air pollution including NO and NO could have a potentially considerable effect on lowering schizophrenia incidence at the population level. Further investigations are necessary to establish a causal relationship.

FUNDING

Lundbeck Foundation, Stanley Medical Research Institute, European Research Council, NordForsk, Novo Nordisk Foundation, National Health and Medical Research Council, Danish National Research Foundation.