In a recent study published in the journal Gut, a team of researchers conducted an Asian-Pacific population-based study and was able to identify an association between immunological, hygiene and dietary factors in childhood with an increase in the risk for developing inflammatory bowel disease.
The incidence of IBD has increased dramatically over the past half century. Although more than 160 genetic risk loci have been identified that underlie disease predisposition, these loci have not completely explained the disease etiology. Striking epidemiological observations including the rising incidence in developing countries and the increased risk of disease in migrant populations implicate the importance of environmental influences on genetic predisposition. In the West, smoking represents one of the most consistently reported risk factors for Crohn’s disease (CD), while data are more conflicting for other factors including appendectomy,tonsillectomy, breast feeding and antibiotic use.
In the study titled “Environmental risk factors in inflammatory bowel disease: a population-based case-control study in Asia-Pacific,” Slew Ng from the Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Institute of Digestive Disease, Li Ka Shing Institute of Health Science, Chinese University of Hong Kong in China and colleagues confuted a population-based study as part of the Asia-Pacific Crohn’s and Colitis Epidemiology study (ACCESS) to evaluate the risk factors for the development of IBD in patients from Indonesia, Malaysia, Sri Lanka, Hong Kong, Thailand, China, Macau, Singapore, and Australia.
The analysis included a total of 442 IBD patients (58% ulcerative colitis; 42% Crohn’s disease) and 940 controls. All participants completed a questionnaire from the International Organization of on environmental factors for IBD.
Results showed that protective factors for Crohn’s disease in Asians were: antibiotic use before age 15 years, being breast-fed for a year or longer, engaging in daily physical activity, having dogs during childhood and daily tea consumption.
In Australians, antibiotic use, having dogs, breast-feeding, and drinking tea were all protective factors against Crohn’s disease.
In Asians, the results showed that the protective factors against ulcerative colitis development in Asians were: having aquarium fish, drinking tea daily, antibiotic use in childhood, being breast-fed for a year or longer, having in-house water tap during childhood, drinking coffee daily, having hot water tap during childhood, and having a flush toilet during childhood.
Having aquarium fish, antibiotic use, breast feeding, having a hot water tap or having a flush toilet were also protective factors for the development of ulcerative colitis in Australians.
When the researchers combined the statistical analysis for both Asians and Australians, the results revealed that bacille Calmette-Guérin tuberculosis vaccine increased risk for Crohn’s disease development, however, they also found that pertussis vaccine decreased risk for the development of ulcerative colitis. The results also showed that smoking increased risk for Crohn’s disease development by more than four times in Australians, while ex-smoking increased risk for the development of ulcerative colitis in both Asians and Australians.
“In conclusion, we reported for the first time in a population-based cohort in Asia-Pacific the role of dietary and immunological alterations early in life and development of IBD,” the researchers wrote according to a recent news release. Crohn’s disease and ulcerative colitis “share overlapping environmental factors. We found a duration-response protective association between breast feeding and disease development, and contact with childhood pets is a novel protective factor. These observed associations indicate that early childhood factors and markers of altered intestinal microbiota including antibiotic use may modulate the risk of IBD later in life and that this period requires further evaluation.”
“These are the first large prospective data on environmental factors from Asia, which, surprisingly, are in concordance with data reported previously from Caucasian populations from Western Europe and North America,” Peter Laszlo Lakatos, MD, from Semmelweis University in Hungary, and Johan Burisch, MD, from Hvidovre University Hospital in Denmark, wrote in a related editorial. “The study has several advantages,” including its design, vigorous matching of controls and use of a questionnaire used frequently in previous studies.
“On the other hand, the study of environmental factors in such a setting is a treacherous path,” they wrote. “The … questionnaire has never been validated” and may not perform well across different environments; some “potentially important questions” were omitted; the interpretation of questions may have been culturally variable; the country-level data are small and national or ethnic variation may be undetectable; and the combination of Asian and Australian data, as well as their prediction based on first-year incidence data “that the authors were only able to include approximately 50%-55% of the incident cases” may introduce biases.”
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