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Childhood exposure to nitrogen dioxide associated with risk for schizophrenia

There was a significant correlation between childhood exposure to nitrogen dioxide and the polygenic risk score for schizophrenia, according to findings published by JAMA Network Open.

Researchers used data from the Danish Civil Registration System to conduct a population-based cohort study that included individuals with schizophrenia and a randomly selected subcohort. They identified singletons bortn between May 1, 1981, and December 31, 2005, who were followed from their 10th birthday until schizophrenia diagnosis, emigration, death or Dec. 31, 2012. The data set contained 23,355 individuals of whom 3,531 were diagnosed with schizophrenia during the study.

“We estimated the mean daily childhood NO₂ exposure and polygenic risk score for schizophrenia cases and noncases after adjustment for age, sex, birth year, parental history of psychiatric disorder and parental socioeconomic position,” Henriette Thisted Horsdal, MSc, PhD, senior researcher at the National Centre for Register-based Research at Aarhus University, Denmark, and colleagues wrote.

To measure exposure to NO₂, researchers recorded a complete history of current and former residential addresses of participants including dates of changes in locations for each individual in their first 10 years of life. The mean daily NO₂ concentrations were calculated accounting for residential changes for each participant. DNA from dried blood spot samples from the Danish Newborn Screening Biobank was genotyped and used to calculate polygenic risk score analysis.

“To our knowledge, this case-cohort study is the first t examine the joint effect of childhood NO₂ exposure and polygenic risk score for schizophrenia on developing schizophrenia,” the authors wrote.

Results showed that individuals with schizophrenia had greater exposure during childhood to NO₂ and a higher polygenic risk score for schizophrenia. The polygenic risk score for schizophrenia explained 0.61% of the variation in childhood NO₂ exposure.

The researchers found correlations between childhood NO₂ exposure and the risk of developing schizophrenia. The heightened risk for schizophrenia associated with higher NO₂ levels is consistent with previous findings from other studies.

“I’m very pleased that we had the unique possibility to combine data on air pollution with genetic information at the individual level by using the detailed and extensive population-based Danish registries and databases,” Horsdal told Healio Psychiatry. – by Erin T. Welsh

Disclosure: Horsdal reports no relevant financial disclosures. Please see the full study for all other authors’ relevant financial disclosures.