炎症性腸疾患の疫学

The Epidemiology to Inflammatory Bowel Disease

炎症性腸疾患〔IBD ; 潰瘍性大腸炎（UC），Crohn病（CD）〕は，難病・特定疾患に指定されており，患者は認定を受ける際に臨床調査個人票を提出する．臨床調査個人票の電子化データを用いた疫学指標の算出は，問題点はあるものの例数が多く，重要と考えられる．本稿では，臨床調査個人票を用いて有病率や患者特性を集計し海外と比較した．年齢調整有病率（10万人当たり）はUC 84.5，CD 26.3（2009年）であり，以前と比較して増加している．有病率は，アジアや途上国では増加しており，原因として生活様式の近代化や診断技術の進歩，死亡率の低下などの要因が考えられる．一方，欧米での有病率はプラトーに達したとの報告もあり，日本での動向に注意が必要である．

　IBD〔inflammatory bowel disease ; UC（ulcerative colitis）, CD（Crohn's disease）〕has been included in the“intractable diseases”defined by the Japanese Ministry of Health, Labour and Welfare. Most patients submit a designated registration form annually to the prefectural government in their residential area in order to be subsidized for treatment. After being converted into electronic expression, the collected data can be used for epidemiological research. Here we calculated the prevalence of IBD in Japan and examined patients'characteristics using the electronic data. Then, the date compared with that of foreign countries. Age-adjusted prevalence per 100,000 people was 84.5 for UC and 26.3 for CD in 2009. The prevalence is still increasing with time in Asia including Japan and the developed countries. Possible causes of the increase are westernized lifestyle, advances of diagnostic technology and decreasing mortality. On the other hand, as some studies reported, the prevalence in Europe and the U.S. has reached a plateau, so we should follow the IBD prevalence data in Japan carefully.