Inflammatory Bowel Disease in Asia: A Second Chance at Uncovering Environmental Factors

Lindsey Konkel

Disclosures

Environ Health Perspect. 2016;124(3):a49 

In This Article

Introduction

When Siew Ng left Malaysia in the early 1990s to study medicine and gastroenterology in London, inflammatory bowel disease (IBD) was practically nonexistent in her native state of Penang and across much of Asia. But on a single day in the fall of 2015, she saw four patients newly diagnosed with Crohn's disease at the Prince of Wales Hospital in Hong Kong. "It seems that patients with IBD are dropping from the sky," says Ng, now a gastroenterologist at The Chinese University of Hong Kong.

Thirty years ago, fewer than 1 in 1 million people in Hong Kong had IBD[1]—the blanket term physicians use to refer to Crohn's disease and a related condition called ulcerative colitis. Both of these immune-mediated diseases lead to chronic gut inflammation that often results in surgery (irritable bowel syndrome, despite its similar name, is a separate, noninflammatory condition). Today roughly 3 in 100,000 people in Hong Kong have a new diagnosis of IBD.[2] Ng and others call the dramatic increase in IBD cases in Hong Kong alarming.

As with many autoimmune diseases, the causes of IBD remain unclear.[3,4] Genetic factors, unlike the environment, cannot shift in the span of a single generation, so genes alone can't explain the recent rise of IBD in non-Western countries. And like many chronic diseases, IBD appears to be the consequence of a complex set of interactions between genes and the environment, an interplay that appears to be modulated by microbes that make their home in the human gut.[5,6]

Despite recent increases, IBD is still relatively rare in Hong Kong and other parts of Asia compared with North America, Europe, Australia, and New Zealand, where the prevalence of IBD averages about 500 in every 100,000 people in the general population.[1] The incidence of autoimmune and inflammatory diseases increased drastically in the developed countries of northern Europe and North America during the second half of the twentieth century.[7] It appeared to be a problem primarily among white people of European descent, but that demographic picture is changing.[7]

"If you look back at the medical literature from a hundred years ago, the rise of IBD—where it was first described in the UK—bears an uncanny resemblance to what we are now witnessing in Hong Kong and across parts of Asia," says Gil Kaplan, an epidemiologist and gastroenterologist at the University of Calgary who specializes in the global rise of IBD.

Although studies of IBD in Asia are in their infancy, early findings suggest a picture similar to what has been observed in North America. The fingerprints of rapid industrialization—the Westernization of diets, subsequent changes to the gut microbiome, exposure to increased levels of pollution, and even improvements in hygiene and health care—may be linked to IBD risk.[7,8] Now Ng and others across Asia and North America are homing in on newly vulnerable populations in search of environmental causes and risk factors—a quest that could ultimately advance efforts to prevent IBD and other chronic inflammatory and autoimmune diseases.

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