PT - JOURNAL ARTICLE AU - Ishaan Dave AU - Brandon Estroff AU - Talia Gergely AU - Christina A. Rostad AU - Lori A. Ponder AU - Courtney McCracken AU - Sampath Prahalad TI - Impact of the Season of Birth on the Development of Juvenile Idiopathic Arthritis in the United States: A Nationwide Registry-based Study AID - 10.3899/jrheum.201238 DP - 2021 Dec 01 TA - The Journal of Rheumatology PG - 1856--1862 VI - 48 IP - 12 4099 - http://www.jrheum.org/content/48/12/1856.short 4100 - http://www.jrheum.org/content/48/12/1856.full SO - J Rheumatol2021 Dec 01; 48 AB - Objective Autoimmune disorders result from the interplay of genetic and environmental factors. Many autoimmune disorders are associated with specific seasons of birth, implicating a role for environmental determinants in their etiopathology. We investigated if there is an association between the season of birth and the development of juvenile idiopathic arthritis (JIA).Methods Birth data from 10,913 children with JIA enrolled at 62 Childhood Arthritis and Rheumatology Research Alliance Registry sites was compared with 109,066,226 US births from the same period using a chi-square goodness-of-fit test. Season of birth of the JIA cohort was compared to the US population estimate using a 2-sided 1-sample test for a binomial proportion and corrected for multiple comparisons. Secondary analysis was performed for JIA categories, age of onset, and month of birth.Results A greater proportion of children with JIA were born in winter (January–March) compared to the US general population (25.72% vs 24.08%; corrected P < 0.0001). This observation was also true after stratifying for age of onset (≤ or > 6 yrs). When analyzed by the month of birth, a greater proportion of children with JIA were born in January compared to the US population (9.44% vs 8.13%; corrected P < 0.0001).Conclusion Relative to the general population, children with JIA are more often born in the winter, and specifically in the month of January. These observations support the hypothesis that seasonal variations in exposures during the gestational and/or early postnatal periods may contribute to development of JIA.