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 two years preceding UC diagnosis. We defined subgroups of
persistent smokers and smokers who quit within 2 years after diagnosis. We compared rates of
overall corticosteroid use, corticosteroid-requiring flares, corticosteroid dependency, thiopurine
use, hospitalization 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 corticosteroidrequiring 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), hospitalization (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, hospitalization 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, hospitalization 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.