ESPE Abstracts

Backgrounds and Aims: Several previous studies have suggested an association between exposure to air pollution and thyroid hormone levels. But epidemiological evidence on the association between fine particulate matter (PM_2.5) and onset of autoimmune thyroid diseases (AITD) in children and adolescents is scarce. This study aimed to identify the association between long-term exposure PM_2.5 and onset of AITD in children and adolescents of South Korea.

Methods: Between 2008 and 2010, we analysed 1,464,571 children aged six years old from the National Health Information Database. We defined the onset of two AITD based on 10^th revision of International classification of Disease (Hashimoto thyroiditis: E063 and Graves disease: E050). We excluded individuals with missing information on age, residence, and income level. Additionally, we excluded individuals with underlying disease (Celiac disease, Addison’s disease, Type 1 diabetes mellitus, Tuberous sclerosis, lymphoid leukemia, polyglandular dysfunction, and congenital hypothyroidism). We followed up the study subjects up to the age of 19. We categorized PM_2.5 into quartile groups and estimated the Hazard Ratio (HR) with 95% confidence interval (CI) comparing the lowest quartile to the others using Cox proportional hazard regression. All models were stratified by gender.

Results: A total of 1,402,863 children aged six years between 2008 and 2010 were analysed. Among them, 2,367 cases (0.17%) of onset Hashimoto thyroiditis and 3,442 cases (0.25%) of onset Graves disease were identified during follow-up period. Long-term exposure to PM_2.5 were significantly associated with AITD [HR_{2nd Quartile} for Hashimoto thyroiditis: 1.16 (95% CI: 1.01, 1.34), HR_{3rd Quartile} for Hashimoto thyroiditis: 1.25 (95% CI: 1.04, 1.50), HR_{4th Quartile} for Graves disease: 1.23 (95% CI: 1.03, 1.46)] in girls. Whereas, no significant association were observed in boys.

Conclusions: This study found only limited evidence for the hypothesis that long-term exposure for PM_2.5 increases the risk of AITD in children and adolescents.