Inflammatory bowel disease: Is East really differ from West?

When I was a medical student, I was taught to believe that inflammatory bowel disease (IBD) should never be diagnosed in the East. When we saw a patient presenting with bloody diarrhea, we thought of amoebiasis, bacterial dysentery or even viral infection (e.g. cytomegalovirus) instead of ulcerative colitis (UC). If we saw a patient presenting with features of Crohn's disease, this was most likely a case of intestinal tuberculosis. However, things have changed and changed dramatically since then. Today, the rising incidence of IBD in Asia is an undisputable phenomenon, with both UC and CD incidence going up in the past decades.1 In fact, most Asian countries have witnessed a twofold to threefold increase in IBD incidences, and the number is still on the rise. In this issue of the Journal, Mak et al.2 compared the epidemiology of IBD in the East to the West. The authors pointed out that in the East, CD seems to rise more rapidly than UC, and urban areas seems to have more IBD than rural countries, and males seems to have more IBD than females. However, the authors also acknowledged that variations in incidence occur in large countries such as China. The size and nature of diseased populations in these studies may also affect the reported incidence and pattern of IBD. Therefore, these so-called disparities should be interpreted with care. To compare the presentation and course of IBD, one has to take into account of access to health care services and duration of follow up. An efficient and affordable health care service often facilitates early presentation of IBD with fewer complications (such as penetrating disease and stricture). Awareness of family doctors about the features of IBD and its rising incidence in the East may also prompt early diagnosis. Furthermore, threshold for hospitalization and need for surgery in IBD flares and complications vary from country to country. Development of colorectal cancer from IBD takes time and occurs usually in long-standing active disease. Therefore, a relative high incidence of complicated IBD (penetrating and structuring disease), a low hospitalization and surgery rate, and a low incidence of colorectal cancer reported so far in the East can be related to cultural, social, and economic reasons rather than biological differences. In Asia, at least 10 years ago, it is not uncommon to see a patient presenting with perforation of bowel after suffering from abdominal pain and change in bowel habit for years receiving treatments by various doctors as conditions other than Crohn's disease. While there are limitations in comparing patient demography and clinical presentations, there are two important aspects to study in IBD and compare between the East and the West. First, is there any environmental factor(s) that may precipitate the rapidly rising trend of IBD among Asian countries? If this (these) factor(s) can be identified, would it be possible to prevent IBD by mitigating the causal factor(s) in the East? Admitting that there are still a lot of uncertainty on environmental factors in IBD, the authors pointed out that promoting breast feeding, avoidance of antibiotic usage in the young, reducing intake of red meat, sucrose, and other artificial food additives may promise as modifiable factors to avoid development of IBD. All these factors seem to be linked to the microbiota of the gut, which, as more evidence is unveiling, is likely to be the key trigger for chronic inflammation in the intestinal mucosa.3 As more interventional studies have provided evidence, even disease remission and relapse in IBD are associated with microbial changes in both mucosal and luminal microbiota.4 Missing or depleted protecting microbes (such as Firmicutes and other butyrate producing species) or excess of pathogenic microbes (Proteobacteria, Fusobacteria, and mucin degrading species) can probably explain why diet, physical activities, antibiotic usage, and breast feeding are correlated with IBD development.5 I think this will be an area of fruitful basic research and clinical trials. As we are still seeing the dawn of the IBD in the East, we may still have a golden opportunity to proof that, by modifying environmental factors, the rising incidence of IBD can be capped. The other important aspect is obviously genetic factors. The authors pointed out that, from genome-wide association studies, most of the mutations found among IBD patients in the West are not overlapping with the mutations found in the East. Does it mean that IBD in the West is actually a different condition (or spectrum of conditions) compared to IBD in the East? I do not think we have an answer to this question yet. After all, we may argue that even UC or CD in the West are not single disease entities. The mutations found related to these conditions only constitute a small percentage of the IBD patient populations.6, 7 The alarming rising speed in IBD incidence over the past two to three decades implies that this rapid change in epidemiology is likely to be related to environmental changes rather than to genetic forces. Genetic factors probably play only a relatively minor role in modifying the epidemiology of IBD. The study of IBD and comparing epidemiology between the West against the East is an interesting but complicated exercise. As the disease is emerging in the East, we should not miss the opportunity to unveil some of the unknown mechanisms and potential intervention to prevent and better manage this devastating disease of the gut.