Environmental Risk Factors and Early-Life Exposures in Juvenile Idiopathic Arthritis: A Case-Control Study

Objective. Juvenile idiopathic arthritis (JIA) is a heterogeneous group of disorders characterized by chronic arthritis in children with unknown etiology. Although research evaluating environmental or early-life exposures in JIA is scarce, there are data to suggest that infections, smoking exposure, and lack of breastfeeding play a role. This case-control study investigated the association of selected environmental and early-life risk factors with the development of JIA. Methods. JIA cases were identified at a major pediatric rheumatology outpatient clinic. Each case was asked to identify up to 3 healthy playmates of similar age and same sex to serve as controls. Parents/caregivers of cases and controls completed a questionnaire on selected environmental and early-life exposures. Conditional logistic regression adjusted for age and socioeconomic status was used to determine the odds ratio (OR) for developing JIA with 95% confidence intervals (95% CIs) for the playmate-matched design. Results. Included in the study were 225 JIA cases and 138 controls. Compared to playmate-matched controls, preterm delivery (OR 1.8 [95% CI 1.2-2.7]) was associated with JIA. There was no association between JIA and household smoking or maternal prenatal smoking, breastfeeding, hospitalization with infection in the first year of life, daycare attendance before 6 years of age, household pets, or residential area prior to the onset of JIA. Conclusion. There was no association between the previously reported risk factors of smoking, early-life infection, or breastfeeding and development of JIA in this study. The association of preterm delivery with JIA needs to be further studied.