Cigarette smoking increases the risk of seropositive adult rheumatoid arthritis. The relationship of smoking with juvenile idiopathic arthritis (JIA), a heterogeneous group of 7 mutually exclusive categories of chronic childhood inflammatory arthritides, is unknown. Our objective was to evaluate the association between JIA and its categories with maternal prenatal smoking.
This case-control study used International Classification of Diseases, Ninth Revision codes from hospital records to identify 1,196 JIA cases born in Washington state and diagnosed at a quaternary pediatric center from 1997-2010. Controls (n = 5,618) were randomly selected from birth records of children without JIA, frequency matched on birth year. Prenatal smoking exposure was assessed from subjects' birth certificates. Chart review categorized JIA into International League of Associations for Rheumatology categories. Adjusted odds ratios (OR) and 95% confidence intervals (95% CIs) were calculated using logistic regression.
We did not observe an increased risk of JIA in relation to maternal prenatal smoking. Prenatal smoking was reported less often among mothers of JIA cases (11%), than among control mothers (17%; OR 0.71 [95% CI 0.58-0.87]), a relationship somewhat more marked for oligoarticular/extended oligoarticular JIA. Although this relationship persisted after adjustment, we cannot rule out that the effect may have been due to residual confounding by socioeconomic status.
We did not observe an increased risk of JIA or its individual categories with maternal prenatal smoking.