Smoke Damage Hits Low and Long

Crohns disease and ulcerative colitis risk goes up with cigarette smoking

(RxWiki News) Damage from smoking can creep below our lungs. Our stomachs can hurt, the pain can spread into the colon, and the pain can stay even if we quit.

A new study found that smoking increases the chance of developing Crohn's disease. And those who used to smoke have a higher risk of developing ulcerative colitis.

"Quit smoking today - your doctor can help."

The authors, led by Leslie Higuchi, MD, a physician in the Division of Gastroenterology and Nutrition at the Children's Hospital Boston, aimed to figure out the connection between cigarette smoking, especially quitting, on the chance of developing Crohn's disease and ulcerative colitis.

Both are inflammatory bowel diseases that cause pain in the stomach and lining of the colon.

Researchers surveyed 229,111 women in the Nurses' Health Study and Nurses' Health Study II over a 32-year span.

The nurses ranged in age from 25-55. The researchers excluded those who did not complete the survey.

Every two years, researchers collected data on when patients started smoking, how much they smoked per day, any diagnoses of Crohn's or ulcerative colitis, and other possible causes for the diseases.

The amount of exposure to cigarette smoke was measured in pack-years, which is smoking a pack containing 20 cigarettes each day for a year.

The number of pack years was calculated by multiplying the number of packs smoked per day by the number of years it took to smoke that amount.

Researchers documented 336 patients with Crohn's and 400 patients with ulcerative colitis.

They found that current and former smokers developed Crohn's 1.9 and 1.35 times more often when compared to those who never smoked.

For ulcerative colitis, smokers would actually develop it less often than non-smokers, 0.86 times as often. But for former smokers, they developed ulcerative colitis1.56 times more often.

The risk of ulcerative colitis triples for those who quit smoking within 2-5 years, and the odds stay high over 20 years.

They did not study if there was a link between the number of cigarettes smoked per day and the risk of the two diseases.

"The distinctly different relationship between cigarette smoking and Crohn's disease from that of smoking and ulcerative colitis underscores the complexity of the pathogenesis of these diseases," the authors said in their report.

"Whereas cigarette smoking consistently heralds an elevated risk of Crohn's, one might speculate that it may suppress risk of ulcerative colitis in a genetically predisposed individual until smoking cessation…"

The authors note several limitations with their study, including that only women in the health profession were part of the data, other possible causes were not taken into account, and participants were only between 25 and 55 years of age.

Though it is not representative of the whole population, the authors say their age-specific data is similar to rates from other US populations.

The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases, the National Institutes of Health, Crohn's and Colitis Foundation of America, Research Fellowship Award, Broad Medical Research Program of the Broad Foundation, the National Cancer Institute and the National Institutes of Health.

They had no role in conducting the study.

The authors served as consultants for various companies that may be a potential competing interest, and one author received research support for the study.

The study was published online July 10 in the American Journal of Gastroenterology.

Review Date: 
September 10, 2012