Background Air pollution could be a potential contributor to autoimmune diseases onset and flare. It has been recently reported by our group in juvenile systemic lupus erythematosus and dermatomyositis, and was rarely studied in Juvenile idiopathic arthritis (JIA) population.
Objectives To evaluate the influence of exposures to inhaled environmental factors during pregnancy and after birth to beginning of disease on JIA diagnosis in residents of a large city.
Methods A case-control study comprising 28 JIA and 56 controls matched by age and gender, residents in the metropolitan region of São Paulo. Daily concentrations of inhaled particulate matter (PM10), sulphur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), and carbon monoxide (CO) were evaluated during gestational period. A structured and reliable questionnaire (kappa index for test-retest of 0.81) assessed demographic data and environmental inhalation exposure during pregnancy and after birth (occupational exposure to demolition, chalk, construction or quarry dust, paints, varnish, gasoline vapor or battery fluids; the presence of industrial activities or gas station near the mother's home/work and/or children's school, maternal tobacco exposure and exposure to tropospheric pollutants).
Results The mean current age was similar in JIA and controls (12.11±4.366 vs.12.02±4.507 years, p=0.93). “Fetal smoking” (mother's second and smoke exposure and/or smoking mothers at home) during pregnancy was significantly higher in JIA patients versus controls (54%vs.17%, p=0.01). Moreover, “fetal smoking” more than 20 cigarettes/day and maternal occupational exposure to quarry dust and gasoline vapor were significantly higher in JIA patients (17%vs.1.7%, p=0,014, 25% vs. 7.1%, p=0.029; respectively). Otherwise, maternal occupational exposure and the presence of industrial activities or gas station at mother's work place >200 meters were significantly higher in controls (39.2%vs.73.2%, p=0.003; 17.8%vs.44.6%, p=0.013; respectively). Regarding tropospheric pollutants no positive association was evidenced (p>0.05) during pregnancy. In multivariate analysis during pregnancy, “fetal smoking” and maternal occupational exposure to quarry dust and gasoline vapor remained risk factor for JIA (OR7.42 CI95%2.08-26.53, p=0.002; OR26.63 CI 95%4.28-165.52, p<0.001, respectively) whereas the fact of mother work during pregnancy was protective factor (OR0.122 CI95%0.027-0.542, p=0.006). Regarding period after birth to beginning disease, secondhand smoke, with exposure to secondhand smoke for over 6 years were significantly higher in JIA group (50%vs.21.4%, p=0.008; 25%vs.5.3%, p=0.014), whereas the frequency of children attend school was significantly lower in JIA patients (64.3%vs.92.8%, p=0.002). In multivariate analysis after birth to beginning disease, secondhand smoke had a significantly association with JIA (OR5.7 IC95%1.87-17.4, p=0.002) whereas a negative association was observed in JIA group attend school (OR0.87 IC95%0.021-0.353, p=0.001).
Conclusions Mothers and patients exposure to secondhand tobacco smoking, besides maternal occupational exposure to quarry dust and gasoline vapor may contribute to JIA onset. On the other hand, the fact of mother work during pregnancy and children attend school may be a protective factor for this inflammatory disease.
Disclosure of Interest None declared