ObjectivesWe aimed to investigate the incidence of juvenile idiopathic arthritis (JIA) in the three geographical regions of Norway, and whether potential regional incidence differences are explained by environmental or genetic factors across regions.MethodsWe conducted a register‐based cohort study including all Norwegian children born 2004‐2019, with follow‐up throughout 2020. The JIA diagnosis defined by ≥ 2 ICD‐10 codes for JIA was validated against medical records. The incidence rate (IR) and hazard ratio (HR) for JIA were estimated for all Norway, and for the regions North, Mid, and South. In a sub‐sample from the Norwegian Mother, Father, and Child Cohort Study (MoBa), the genetic risk for JIA was assessed in the three regions.ResultsAfter median 9.1 (range 0.3‐16.0) years of follow‐up, we identified 1184 JIA cases and 910058 controls. The IR for JIA/100 000 person‐years was 14.4 in all of Norway; 25.9 in region North, 17.9 in region Mid and 12.5 in region South. The HR (95% CI) of JIA in region North was 2.07 (1.77‐2.43) and in region Mid 1.43 (1.23‐1.67) compared to region South. Adjustments for perinatal factors, socioeconomic status, and early antibiotic exposure did not change our estimates substantially. In MoBa (238 cases, 57392 controls), the association between JIA and region of birth was no longer significant when adjusting for genetic factors.ConclusionsWe found a higher incidence of JIA with increasing latitude, without evidence for available environmental factors explaining the observed gradient. In contrast, genetic factors modified the association, but further studies are warranted.

中文翻译：

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挪威各纬度幼年特发性关节炎的发病率和遗传风险


目的我们旨在调查挪威三个地理区域的幼年特发性关节炎 （JIA） 的发病率，以及潜在的区域发病率差异是否由不同地区的环境或遗传因素解释。方法我们进行了一项基于登记册的队列研究，包括所有 2004-2019 年出生的挪威儿童，并在 2020 年全年进行随访。根据病历验证了 ≥ 2 个 ICD-10 代码定义的 JIA 诊断。估计了所有挪威以及北部、中部和南部地区的 JIA 发病率 （IR） 和风险比 （HR）。在挪威母亲、父亲和儿童队列研究 （MoBa） 的子样本中，评估了三个地区 JIA 的遗传风险。结果经过中位 9.1 年 （范围 0.3-16.0） 年的随访，我们确定了 1184 例 JIA 病例和 910058 例对照。整个挪威的 JIA/100 000 人年的 IR 为 14.4;北部地区为 25.9，中部地区为 17.9，南部地区为 12.5。与南部地区相比，北部地区 JIA 的 HR （95% CI） 为 2.07 （1.77-2.43），中部地区为 1.43 （1.23-1.67）。对围产期因素、社会经济地位和早期抗生素暴露的调整并没有显着改变我们的估计。在 MoBa （238 例，57392 例对照） 中，在调整遗传因素时，JIA 与出生地区之间的关联不再显著。结论我们发现 JIA 的发病率随着纬度的增加而增加，没有可用的环境因素解释观察到的梯度。相比之下，遗传因素改变了这种关联，但需要进一步的研究。