Risk Factors

Risk Factors

An estimated 1 - 2 million Americans suffer from inflammatory bowel disease (IBD). (This wide statistical variation is due to the difficulty in diagnosing these disorders and because people in remission may not be identified.) It was thought that Crohn's disease was far less common than ulcerative colitis, but currently the incidences of each are estimated to be about equal. The incidence may vary depending on gender, age, and geography:

• Men and women have equal risk for ulcerative colitis.
• IBD is diagnosed most often in young people between the ages of 10 and 19, but it can occur at any age. A smaller peak onset occurs between ages 50 and 80. About 2% of IBD cases appear in children below age 10.
• Ulcerative colitis is most common among people of European descent. People of African descent have a lower incidence than Caucasians. Low incidence regions include Asia and South America. Ethnically, Jewish people have a higher risk.
• Ulcerative colitis may disproportionately affect people of higher socioeconomic classes, but evidence for this is inconclusive.

Factors Associated with a Higher or Lower Risk for Ulcerative Colitis

Smoking. Smokers have lower than average rates of ulcerative colitis (but higher than average rates of Crohn's disease). Some patients with ulcerative colitis, in fact, have reported that their disorder began after they quit smoking, and many studies have reinforced the association between smoking and protection against ulcerative colitis. (This information is certainly no encouragement to smoke. Rather, patients should ask their doctor about trials using nicotine replacement aids.)

Breastfeeding. Breastfeeding appears linked to lower risk for UC.

Left-Handedness. People who are left-handed have a significantly higher risk for both IBDs as well as for certain other diseases associated with immune abnormalities.

Depression. A 2001 study reported that patients with ulcerative colitis were more likely to have a history of depression or anxiety than those without IBD. Some researchers suggest that depression may alter the immune system and make people more susceptible to ulcerative colitis.