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Sibling Exposure and Risk of Juvenile Idiopathic Arthritis
Author(s) -
Miller Jessica,
Ponsonby AnneLouise,
Pezic Angela,
Kemp Andrew,
Piper Susan E.,
Akikusa Jonathan D.,
Allen Roger C.,
Munro Jane E.,
Ellis Justine A.
Publication year - 2015
Publication title -
arthritis and rheumatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.106
H-Index - 314
eISSN - 2326-5205
pISSN - 2326-5191
DOI - 10.1002/art.39129
Subject(s) - sibling , medicine , odds ratio , confidence interval , arthritis , juvenile , population , case control study , protective factor , risk factor , hygiene , immunology , demography , pediatrics , environmental health , pathology , biology , psychology , developmental psychology , sociology , genetics
Objective Susceptibility to juvenile idiopathic arthritis (JIA) is presumed to be determined by both genes and environment. However, the environmental factors remain largely unknown. The hygiene hypothesis suggests that exposure to siblings, as a marker of exposure to microbes in early life, may protect against the development of later immune disorders. Some prior evidence suggests this may also be true for JIA. The present study was undertaken to test this hypothesis in detail. Methods We conducted a comprehensive analysis of the role of sibling exposure in JIA risk within the Childhood Arthritis Risk Factor Identification Study JIA case–hospital control sample (302 cases and 676 controls) from Victoria, Australia. Results We found that, compared to being an only child, having any siblings was protective against JIA, with an adjusted odds ratio (OR) of 0.46 (95% confidence interval [95% CI] 0.28–0.74) ( P = 0.001). The protective association appeared to increase with increasing number of siblings (e.g., for ≥3 siblings, adjusted OR 0.25 [95% CI 0.13–0.48], P < 0.001). A protective association of siblings was also observed when we considered cumulative sibling years by age 6 (e.g., for ≥3 years of exposure versus no exposure, adjusted OR 0.49 [95% CI 0.30–0.79], P = 0.003). We also compared cases to a second control sample (n = 341) collected from the community and weighted to represent the child population of Victoria. Data remained supportive of an association between sibling exposure and protection against JIA, particularly for exposure to younger siblings. Conclusion Increased exposure to siblings is associated with a reduced risk of disease in our sample. This suggests that increased microbial exposure in childhood may confer protection against the development of JIA.