The impact of smoking and smoking cessation on disease outcomes in ulcerative colitis: a nationwide population‐based study

Summary Background Smokers are less likely to develop ulcerative colitis (UC) but the impact of smoking and subsequent cessation on clinical outcomes in UC is unclear. Aim To evaluate the effect of smoking status and smoking cessation on disease outcomes. Methods Using a nationally representative clinical research database, we identified incident cases of UC during 2005‐2016. Patients were grouped as never‐smokers, ex‐smokers and smokers based on smoking status recorded in the 2 years preceding UC diagnosis. We defined subgroups of persistent smokers and smokers who quit within 2 years after diagnosis. We compared the rates of overall corticosteroid use, corticosteroid‐requiring flares, corticosteroid dependency, thiopurine use, hospitalisation and colectomy between these groups. Results We identified 6754 patients with a new diagnosis of UC over the study period with data on smoking status, of whom 878 were smokers at diagnosis. Smokers had a similar risk of corticosteroid‐requiring flares (OR 1.16, 95% CI 0.92‐1.25), thiopurine use (HR 0.84, 95% CI 0.62‐1.14), corticosteroid dependency (HR 0.85, 95% CI 0.60‐1.11), hospitalisation (HR 0.92, 95% CI 0.72‐1.18) and colectomy (HR 0.78, 95% CI 0.50‐1.21) in comparison with never‐smokers. Rates of flares, thiopurine use, corticosteroid dependency, hospitalisation and colectomy were not significantly different between persistent smokers and those who quit smoking after a diagnosis of UC. Conclusions Smokers and never‐smokers with UC have similar outcomes with respect to flares, thiopurine use, corticosteroid dependency, hospitalisation and colectomy. Smoking cessation was not associated with worse disease course. The risks associated with smoking outweigh any benefits. UC patients should be counselled against smoking.