Diet Is the Biggest Environmental Risk Factor in IBD
The strongest environmental influence on inflammatory bowel disease (IBD) globally appears to be diet, though more research is needed, said Dr Charles Bernstein, at the 2018 AIBD Meeting.
Though the highest rates of IBD continue to be in North America, Europe, and Australia, epidemiology data shows a growing incidence in Asia as well. As we look for potential etiologic factors, Dr Bernstein, from the University of Manitoba IBD Clinical and Research Centre, Winnipeg, said a useful approach has been to look for consistency in environmental influence on IBD rates around the world.
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Smoking has been considered a classic risk factor for IBD. In the US, patients with Crohn disease (CD) are more likely to be smokers, and patients with ulcerative colitis (UC) are more likely to be ex-smokers. Smoking also contributes to a worse course of disease. However, in terms of global etiology, Dr Bernstein called the relevance of smoking into question. He pointed out that smoking is not a risk factor in countries where the incidence of IBD is rising the most rapidly, such as India.
A study that directly compared risk across China, India, and the US found that in China, smoking is not a risk factor for CD though prior smoking is for UC; otherwise there was not a strong relationship between risk and smoking in the three countries. Thus, Dr Bernstein concluded that this is not a clear etiologic factor worldwide for IBD.
Dr Bernstein also discussed antibiotic use as a risk factor, with studies showing vastly different bacterial composition in the bowels after antibiotics use and these changes lasting for months. A study by his research group looking at use of antibiotics in the first year of life for children with IBD vs controls found that children with CD were given antibiotics at higher rates, conferring an 80% increased risk. In adults, antibiotic use 2-5 years prior to diagnosis has been associated with adult onset IBD, a 40% increased risk. With studies estimating that one-third of all antibiotic prescriptions are considered inappropriate, providers need to be more cautious.
The research consistently shows that the first year of life is a crucial period for developing IBD risk, Dr Bernstein said, as this is when the gut microbiome develops. Looking at some other proposed risk factors, he said that C section delivery, initiation of breastfeeding after discharge, and incidence of maternal infections warranting antibiotics appear to have no effect.
This implies that events later in childhood are more important for conferring risk. These include infections preceding diagnosis, the aforementioned antibiotics use, and diet. Changes in diet worldwide, particularly the consumption of more processed foods, may be linked to increased risk. Consumption of high fiber foods including fruits and vegetables appears to be protective.
He noted that complementary and alternative medicines may not be just a harmless add-on, as patients are less likely to be adherent to medications with use of these therapies. Probiotics are not beneficial but may not be harmful either.
Finally, Dr Bernstein presented data that patients report stress and worry as major environmental contributors to their disease and flare-ups. A high perception of stress is associated with disease symptoms, raising the importance of the brain-gut connection in this disease and other autoimmune conditions. Patients are also more likely to have a mood disorder several years before onset of IBD. Further research is needed to explore the biology behind this link.
—Kara Rosania
Reference:
Bernstein C. The environment and IBD: what every patient asks, and every clinician should know. Presented at: Advances in Inflammatory Bowel Diseases; December 13-15, 2018; Orlando, FL. https://www.consultant360.com/meetings/aibd.