biostudies-literatureClarke SLNUniversity of BristolMedical Research CouncilWellcome Trust674-681https://www.ebi.ac.uk/biostudies/studies/S-EPMC7617134biostudies-literatureUnknown75(3)<h4>Objectives</h4>Observational studies report mixed findings regarding the association between vitamin D and juvenile idiopathic arthritis (JIA) incidence or activity; however, such studies are susceptible to considerable bias. Because low vitamin D levels are common within the general population and easily corrected, there is potential public health benefit in identifying a causal association between vitamin D insufficiency and JIA incidence. To limit bias due to confounding and reverse causation, we examined the causal effect of the major circulating form of vitamin D, 25-hydroxy vitamin D (25-[OH]D), on JIA incidence using Mendelian randomization (MR).<h4>Methods</h4>In this 2-sample MR analysis, we used summary level data from the largest and most recent genome-wide association studyArthritis care & researchVitamin D Levels and Risk of Juvenile Idiopathic Arthritis: A Mendelian Randomization Study.PMC7617134211030203918MR/R013926/1MC‐UU‐00011‐5203918/Z/16/ZMR/S009310/1MC_UU_00032/4MC_UU_00011/5211030/Z/18/ZRamanan AVSharp GCRelton CLClarke SLNMitchell REfalseVitamin D Levels and Risk of Juvenile Idiopathic Arthritis: A Mendelian Randomization Study.<h4>Objectives</h4>Observational studies report mixed findings regarding the association between vitamin D and juvenile idiopathic arthritis (JIA) incidence or activity; however, such studies are susceptible to considerable bias. Because low vitamin D levels are common within the general population and easily corrected, there is potential public health benefit in identifying a causal association between vitamin D insufficiency and JIA incidence. To limit bias due to confounding and reverse causation, we examined the causal effect of the major circulating form of vitamin D, 25-hydroxy vitamin D (25-[OH]D), on JIA incidence using Mendelian randomization (MR).<h4>Methods</h4>In this 2-sample MR analysis, we used summary level data from the largest and most recent genome-wide association study2023-01-01T00:00:00Z2023 Mar2025-04-03T23:56:02.659Z2025-04-03T23:56:02.659ZS-EPMC76171343474829110.1002/acr.24815