Impact of Smoking and Smoking Cessation on Ulcerative Colitis Disease Outcomes

Ulcerative colitis. Coloured X-ray of the abdomen of a 30 year old man with ulcerative colitis. This is an inflammation and ulceration of the colon that causes bloody diarrhoea and abdominal pain. This is a severe case affecting the whole colon. The cause of ulcerative colitis is not known. Treatment is with anti-inflammatory drugs and in severe cases surgical removal of the colon.
Smoking is not associated with a beneficial impact in disease outcomes in UC. Furthermore, we found no evidence that smoking cessation impacts adversely on subsequent clinical outcomes.

According to a study published in Alimentary Pharmacology and Therapeutics, smokers and never-smokers with ulcerative colitis (UC) have similar disease outcomes with respect to colectomy, hospitalization, corticosteroid dependency, thiopurine use, and flares, while quitting smoking is not associated with worse disease course. Thus, clinicians should counsel newly diagnosed patients with UC against smoking and smokers should be encouraged to quit. Although it is known that smokers are less likely to develop UC, the impact of smoking and quitting smoking on UC disease outcomes is unclear. The current study used a nationally representative clinical research database to identify a retrospective incident cohort of patients diagnosed with UC from 2005 to 2016 to evaluate this impact. The Clinical Practice Research Datalink (CRPD) contains longitudinal, patient-level, anonymized electronic health records from approximately 8% of general practices in the UK. Patients were categorized as smokers, ex-smokers, and never-smokers based on the status reported in the 2 years before the first record of UC diagnosis. Between-group comparisons were made of colectomy, hospitalization, thiopurine use, corticosteroid-requiring flares, corticosteroid use, and corticosteroid dependency, with corticosteroid use as a proxy measure of a corticosteroid-requiring flare-up as the primary outcome.

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Among a total 9616 patients with newly diagnosed UC, 6754 had available smoking data. At time of diagnosis, 39.9% (n=2698) were never-smokers, 47.1% (n=3178) were ex-smokers, and 13% (n=878) were smokers. During the 12-year study period, the proportion of smokers at diagnosis remained stable. The cumulative risk of corticosteroid use among never smokers was 27.9%, 34.8% and 37.1% at 1, 3 and 5 years, respectively. This risk was similar among ex-smokers and smokers (P =.36 and =.21, respectively). A similar risk in smokers compared with never-smokers was seen for colectomy (HR, 0.78; 95% CI, 0.50‐1.21), hospitalization (HR, 0.92; 95% CI, 0.72‐1.18), corticosteroid dependency (HR, 0.85; 95% CI, 0.60‐1.11), thiopurine use (HR, 0.84; 95% CI, 0.62‐1.14), and corticosteroid‐requiring flares (OR, 1.16; 95% CI, 0.92‐1.46). Risks seen in persistent smokers vs quitters for crude oral corticosteroid use were similar: 35.7% vs 45.9% (P =.02), and similar risks of corticosteroid flares were seen in quitters compared with persistent smokers (OR, 1.13; 95% CI, 0.66‐1.94; P =.66). No significant difference was seen between quitters vs persistent smokers in rates of thiopurine, corticosteroid dependence, hospitalization, and colectomy.

Study limitations included using a cross-sectional marker of smoking status, a lack of smoking data on 30% of UC patients in the two years before diagnosis, and a lack of information on endoscopic or inflammatory markers of disease activity.

The study investigators concluded, “Our findings, taken together with those of others, support the view that smoking is not associated with a beneficial impact in disease outcomes in UC. Furthermore, we found no evidence that smoking cessation impacts adversely on subsequent clinical outcomes. These are important observations since evidence suggest that some patients believe smoking has a beneficial effect on the disease course of UC… Our findings should therefore embolden clinicians to advise against smoking and reassure patients who already smoke that they can benefit from the many advantages of smoking cessation without risk of worsening their UC.”


Blackwell J, Saxena S, Alexakis C, et al. The impact of smoking and smoking cessation on disease outcomes in ulcerative colitis: a nationwide population-based study [published online August 6, 2019]. Aliment Pharmacol Ther. doi: 10.1111/apt.15390