Piovani D, Pansieri C, Kotha SRR, Piazza AC, Comberg CL, Peyrin-Biroulet L, Danese S, Bonovas S. Ethnic Differences in the Smoking-related Risk of Inflammatory Bowel Disease: A Systematic Review and Meta-analysis.
J Crohns Colitis 2021;
15:1658-1678. [PMID:
33721889 DOI:
10.1093/ecco-jcc/jjab047]
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Abstract
BACKGROUND AND AIMS
The association between smoking and inflammatory bowel disease [IBD] relies on old meta-analyses including exclusively non-Jewish White populations. Uncertainty persists regarding the role of smoking in other ethnicities.
METHODS
We systematically searched Medline/PubMed, Embase, and Scopus for studies examining tobacco smoking and the risk of developing IBD, ie, Crohn's disease [CD] or ulcerative colitis [UC]. Two authors independently extracted study data and assessed each study's risk of bias. We examined heterogeneity and small-study effect, and calculated summary estimates using random-effects models. Stratified analyses and meta-regression were employed to study the association between study-level characteristics and effect estimates. The strength of epidemiological evidence was assessed through prespecified criteria.
RESULTS
We synthesised 57 studies examining the smoking-related risk of developing CD and UC. Non-Jewish White smokers were at increased risk of CD (29 studies; relative risk [RR]: 1.95, 95% confidence interval [CI]: 1.69‒2.24; moderate evidence). No association was observed in Asian, Jewish. and Latin-American populations [11 studies; RR: 0.97; 95% CI: 0.83-1.13], with no evidence of heterogeneity across these ethnicities. Smokers were at reduced risk of UC [51 studies; RR: 0.55, 95% CI: 0.48-0.64; weak evidence] irrespectively of ethnicity; however, cohort studies, large studies, and those recently published showed attenuated associations.
CONCLUSIONS
This meta-analysis did not identify any increased risk of CD in smokers in ethnicities other than non-Jewish Whites, and confirmed the protective effect of smoking on UC occurrence. Future research should characterise the genetic background of CD patients across different ethnicities to improve our understanding of the role of smoking in CD pathogenesis.
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