Abstract
Background and aimsThe effect of smoking on the risk of developing inflammatory bowel diseases (IBD) may be heterogeneous across ethnicity and geography. Although trends in smoking for the general population are well described, it is unknown whether these can be extrapolated to the IBD cohort. Smoking prevalence trends specific to the global IBD cohort over time have not been previously reported. This is a systematic review of smoking prevalence specific to the IBD cohort across geography.MethodsA systematic literature search was conducted on Medline and Embase from January 1st 1946 to April 5th 2018 to identify population-based studies assessing the prevalence of smoking at diagnosis in inception cohorts of Crohn’s disease(CD) or ulcerative colitis(UC). Studies that did not report smoking data from time of diagnosis or the year of IBD diagnosis were excluded. Prevalence of smoking in IBD was stratified by geography and across time.ResultsWe identified 56 studies that were eligible for inclusion. Smoking prevalence data at diagnosis of CD and UC was collected from twenty and twenty-five countries respectively. Never-smokers in the newly diagnosed CD population in the West has increased over the last two decades, especially in the United Kingdom and Sweden; +26.6% and +11.2% respectively. Never-smokers at CD diagnosis in newly industrialised nations have decreased over the 1990s and 2000s; China (-19.36%). Never-smokers at UC diagnosis also decreased in China; -15.4%. The former-smoker population at UC diagnosis in China is expanding; 11%(1990–2006) to 34%(2011–2013).ConclusionThere has been a reduction in the prevalence of smoking in the IBD cohort in the West. This is not consistent globally. Although, smoking prevalence has decreased in the general population of newly industrialised nations, this remains an important risk factor with longer term outcomes awaiting translation in both UC and CD.
Highlights
Our group has extensively reported that inflammatory bowel diseases (IBD) have become a global challenge in the 21st century.[1,2,3,4,5] The rapidly accelerating incidence of both Crohn’s disease (CD) and ulcerative colitis (UC) in the newly industrialized countries in the East mirrors epidemiological patterns of IBD in the West more than 75 years ago.[2]
A systematic literature search was conducted on Medline and Embase from January 1st 1946 to April 5th 2018 to identify population-based studies assessing the prevalence of smoking at diagnosis in inception cohorts of Crohn’s disease(CD) or ulcerative colitis(UC)
There has been a reduction in the prevalence of smoking in the IBD cohort in the West
Summary
Our group has extensively reported that inflammatory bowel diseases (IBD) have become a global challenge in the 21st century.[1,2,3,4,5] The rapidly accelerating incidence of both Crohn’s disease (CD) and ulcerative colitis (UC) in the newly industrialized countries in the East mirrors epidemiological patterns of IBD in the West more than 75 years ago.[2]. In the West, smoking has been consistently reported as a risk factor for developing CD and adversely affects disease course[7,8,9], whereas former smokers and non-smokers are at increased risk of developing UC in comparison to current smokers.[10,11] In contrast, studies in non-Western populations have been unable to replicate this association between CD and smoking.[12] The interaction between smoking and the NOD-2 gene and their effect on the risk of CD has been postulated to be specific to the 1007 fs mutation and a negative association between NOD-2 mutation and smoking could be explained by their inverse relationship.[13]. Smoking prevalence trends specific to the global IBD cohort over time have not been previously reported. This is a systematic review of smoking prevalence specific to the IBD cohort across geography
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