Department of Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
Expert Rev Gastroenterol Hepatol. 2012 Aug;6(4):445-7. doi: 10.1586/egh.12.31.
Inflammatory bowel diseases (IBDs), such as Crohn's disease and ulcerative colitis, are multifactorial diseases that result from an overly aggressive immune response towards an environmental trigger in a genetically susceptible host. Much has been learned about susceptibility genes; however, environmental triggers are still largely unknown. In the 1990s, a large study from Europe suggested a north-south gradient regarding the incidence of IBD; however, this was never shown convincingly for the USA. In the present study, the authors used and extended data from the Nurses' Health Study I and II and were able to demonstrate that indeed the risk of developing IBD is significantly lower for the southern latitudes of the USA and did not depend on ancestry or lifestyle factors such as smoking. The authors speculate that an increased exposure to sunlight provides protection from IBD via the vitamin D pathway.
炎症性肠病（IBD），如克罗恩病和溃疡性结肠炎，是多因素疾病，是由遗传易感宿主对环境触发因素的过度攻击性免疫反应引起的。人们已经对易感基因有了很多了解；然而，环境触发因素在很大程度上仍然未知。在 20 世纪 90 年代，一项来自欧洲的大型研究表明，IBD 的发病率存在南北梯度；然而，这在美国从未得到令人信服的证明。在本研究中，作者使用并扩展了护士健康研究 I 和 II 的数据，并能够证明，实际上，美国南部地区的 IBD 发病风险显著较低，并且与遗传或生活方式因素（如吸烟）无关。作者推测，增加阳光暴露可通过维生素 D 途径提供对 IBD 的保护。
