Researchers are also reporting that people with inflammatory bowel disease are at increased risk for asthma, arthritis, chronic kidney disease, psoriasis, bronchitis, and other conditions believed to be linked to the immune system.
"These studies remind us that the effects of inflammatory bowel disorders extend to every corner of the body, including the lungs and central nervous system," says Edward Loftus Jr. of the Mayo Clinic, who wrote an editorial accompanying two studies.
"The findings lend credence to the concept that patients with one chronic inflammatory condition are more likely than the general population to develop another."
Ulcerative colitis commonly affects young adults; symptoms can include chronic diarrhea, abdominal cramping, weight loss, and fever. The condition is limited to the lining of the large intestine, and because of this it is curable by surgery that removes the colon. Crohn's disease involves any part of the intestinal tract from the mouth to the anus.
Unlike the poorly understood but more common condition known as irritable bowel syndrome (IBS), IBD is frequently associated with symptoms occurring outside the bowel. These can include inflammation of the eyes, mouth ulcers, joint pain or swelling, and other inflammatory-related conditions.
Link With MS Long Suspected
A link between IBD and multiple sclerosis has been suspected for some time, but earlier studies have been conflicting. Powerful new drugs used to treat IBD, which block inflammation-causing tumor necrosis factor (TNF -- a part of the immune system), are also suspected of causing multiple sclerosis.
Medications that block TNF like Remicade and Humira are now required to contain labels warning of a possible link to multiple sclerosis and similar conditions. But all agree that their role in the disease is far from clear.
In one of the two new studies, University of Pennsylvania School of Medicine researchers compared 20,000 IBD sufferers in the U.K. to 80,000 people with similar characteristics who did not have IBD.
The risk of developing multiple sclerosis or a related disease was 1.7 times higher for the people who had IBD compared with those without IBD.
The researchers characterize the association as "small but significant."
Medications that block TNF had not been introduced at the time the database was compiled, suggesting an independent link between IBD and multiple sclerosis and other MS-like disorders, study co-researcher James D. Lewis, MD, tells WebMD.
"This study does not answer the questions about the safety of this new collection of anti-TNF-alpha therapies and whether IBD patients should or should not use them," he says.
Beyond GI Symptoms
In the second study, researchers in Canada examined the relationship between IBD and a group of common lung and neurological diseases believed to be mediated by the immune system. They did this by examining a database of just over 8,000 patients treated for IBD over a 19-year period. Each patient was matched with 10 people who did not have IBD.
The researchers reported that people with ulcerative colitis or Crohn's disease had modestly elevated risks of having other inflammatory conditions including asthma, arthritis, bronchitis, psoriasis, and heart disease related to inflammation.
Ulcerative colitis, but not Crohn's disease, was linked to a greater risk for multiple sclerosis and chronic kidney disease.
In more than half of the cases, these diseases were diagnosed before the IBD, lending support to the idea that they share a common genetic or environmental cause.
Loftus tells WebMD that the findings highlight the importance of looking beyond gastrointestinal symptoms when treating patients with IBD.
"It is important to treat the whole patient and not just the GI symptoms," he says.