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Prevalence of current, former, and never smoking at diagnosis and association of smoking status with Crohn’s disease and ulcerative colitis by country of recruitment. *Adjusted for sex. OR, odds ratio; NE, not estimable. The reference group of the unadjusted and adjusted ORs consisted of never smokers at diagnosis. The associations of former smoking and CD and UC were not estimable for India due to absolute absence of former smoking CD cases and controls
