Wang P, et al. - Researchers compared the prevalence of smoking at diagnosis between inflammatory bowel disease (IBD) cases and controls recruited in China, India, and the USA, as well as examined the effect of smoking on disease outcomes. Between 2014 and 2018, IBD cases and controls were recruited. For this analysis, all members completed a questionnaire about demographic characteristics, environmental risk factors and IBD history. According to the findings obtained, heterogeneity in the associations of smoking and IBD risk and outcomes between China, India, and the USA was found.