Cigarette Smoke Tied To Colorectal Neoplasia In IBD Patients

While cigarette smoke exposure is associated with an increased risk of colorectal neoplasia in patients with irritable bowel disease (IBD), a new study suggests that the risk may differ for those with ulcerative colitis or Crohn's disease.

Researchers examined data on 1,386 patients with IBD who had at least one pathology report from a colorectal biopsy and provided information on any cigarette exposure, including current and former active smoking as well as passive exposure. Overall, a total of 153 patients (11.5%) were diagnosed with colorectal neoplasia.

Crohn's disease patients were more likely to develop colorectal neoplasia when they were current smokers (hazard ratio 2.20), as well as when they had current or childhood passive smoke exposure (HR 1.87 and 4.79, respectively). The trend for increased risk among former smokers (HR 2.16) wasn't statistically significant.

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Ulcerative colitis patients, however, had an increased risk of colorectal neoplasia when they were former smokers (HR 1.73). Patients with ulcerative colitis did not appear to have an increased risk of colorectal neoplasia with current smoking or with current or former passive smoke exposure, according to the results published in Clinical Gastroenterology & Hepatology.

"Cigarette smoke exposure is, especially in patients with Crohn's disease, a significant risk factor for CRN, even when predictive models are adjusted for known clinical confounders such as extensive colitis and concordant primary sclerosing cholangitis," said lead study author Dr. Kimberley van der Sloot of the Department of Gastroenterology and Hepatology at the University Medical Center Groningen, in the Netherlands.

With Crohn's disease, cigarette smoke exposure may increase inflammation, which in turn raises the risk of colorectal neoplasia, Dr. van der Sloot said by email. Cigarette smoke appeared to have the opposite effect with ulcerative colitis, decreasing inflammation, Dr. van der Sloot added.

"Future research is needed to further explore the role of cigarette smoke exposure in relation to other lifestyle-associated factors known for a role in colorectal neoplasia development in the general population, such as red meat consumption and alcohol use," Dr. van der Sloot said.

One limitation of the study is that participants were from a single tertiary care center, and results may not be generalizable to other populations. Another is the lack of data on how cigarette pack-years or any dose effect of smoke exposure might impact the risk of colorectal neoplasia in IBD patients.

Even so, the study results add to a large body of evidence linking cigarette smoking to a variety of conditions including cancer, cardiovascular disease, and immune mediated diseases like IBD, said Dr. Gilaad Kaplan, a professor of medicine in the division of gastroenterology and hepatology at the Cumming School of Medicine at the University of Calgary, in Alberta, Canada.

"Among those with IBD who are current smokers, I strongly recommend quitting smoking even in those with ulcerative colitis due to the cumulative long-term adverse health effects associated with cigarette smoking," Dr. Kaplan, who wasn't involved in the study, said by email.

"As a gastroenterologist, this is important information to my clinical practice as the findings remind me that I need to ensure enrollment of smokers, and former smokers who are eligible, for colorectal dysplasia surveillance programs for IBD," Dr. Kaplan added.

—Lisa Rapaport

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