Long-Term Air Pollution Affects the Onset of Autoimmune Thyroid Diseases in Children and Adolescents: Evidence from a Nationwide Cohort Study in Korea

Abstract

Background and AimsPrevious studies have suggested a link between exposure to air pollution and thyroid hormone levels. However, epidemiological evidence on the relationship between air pollution and the incidence of autoimmune thyroid diseases (AITD) in children and adolescents remains scarce. This study aimed to investigate the association between long-term exposure to air pollution and the onset of AITD in children and adolescents in South Korea.MethodsThe study included 1,400,433 children aged 6 years at baseline (between 2008 and 2010) from the National Health Information Database, with follow-up until they reached 19 years of age. We defined the onset of AITD based on the 10th revision of the International Classification of Diseases (Hashimoto’s thyroiditis: E063, Graves’ disease: E050). We excluded individuals with missing data on age, residence, income level, or underlying conditions such as congenital hypothyroidism. We categorized exposure concentration of particulate matter (PM10 and PM2.5), nitrogen dioxide (NO2), sulfur dioxide (SO2), and ozone (O3) into quartiles and estimated the hazard ratio (HR) with 95% confidence interval (CI), comparing the lowest quartile to the others using Cox proportional hazards model. All models were gender-stratified to assess risk differences.ResultsAmong the 1,400,433 children analyzed, 2,344 cases (0.17%) of Hashimoto’s thyroiditis and 3,424 cases (0.24%) of Graves’ disease were diagnosed during the follow-up period. Among girls, annual mean PM2.5 exposure (HR3rd Quartile 1.245, 95% CI: 1.035, 1.497, HR4th Quartile 1.286, 95% CI: 1.052, 1.571) was significantly associated with the onset of Graves’ disease, as was SO2 (HR2nd Quartile 1.31, 95% CI: 1.003, 1.277).Among boys, a significant association was observed between average annual NO2 exposure (HR4th Quartile 2.153, 95% CI: 1.214, 3.818), and the onset of Hashimoto’s thyroiditis.ConclusionsOur findings provide evidence that long-term exposure to air pollution is associated with the incidence of AITD in children and adolescents.

Note:
Funding declaration: None

Conflict of Interests: The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper. The authors also declare no conflict of interest with the NHIS.

Ethical Approval: This study was exempted from review by the Institutional Review Board of the Ewha Womans University Seoul Hospital (IRB No: SEUMC 2023-09-008)

Keywords: Air pollution, Autoimmune thyroid disease, Children, Cohort, Fine particulate matter