Association between smoking and risk of primary sclerosing cholangitis: A systematic review and meta-analysis

Background/Objectives: Studies have suggested that smokers may have a lower risk of primary sclerosing cholangitis (PSC) although the results have been inconsistent. This systematic review and meta-analysis was conducted to summarize all available data to better characterize this association. Methods: A comprehensive literature review was conducted using Medline and Embase databases through January 2018 to identify all studies that compared the risk of PSC among current/former smokers versus nonsmokers. Effect estimates from each study were extracted and combined using the random-effect, generic inverse variance method of DerSimonian and Laird. Results: Seven case-control studies with 2,307,393 participants met the eligibility criteria and were included in the meta-analysis. The risk of PSC among current smokers and former smokers was significantly lower than nonsmokers with the pooled odds ratio of 0.31 (95% CI, 0.18-0.53) and 0.52 (95% CI, 0.44-0.61), respectively. The risk remained significantly lower among current smokers and former smokers compared with nonsmokers even when only patients with PSC without inflammatory bowel disease were included. Conclusions: A significantly decreased risk of PSC among current and former smokers was demonstrated in this study.