Smoking & risk of advanced liver fibrosis among patients with primary biliary cholangitis: A systematic review & meta-analysis

Background & objectives: Studies have suggested that smoking may accelerate the progression of fibrosis among patients with primary biliary cholangitis (PBC), although the data are limited. The current review was undertaken with the aim to comprehensively analyze this possible association by identifying all relevant studies and summarizing their results. Methods: A comprehensive literature review on MEDLINE and EMBASE databases was performed from inception through February 2019 to identify all relevant studies. Eligible studies included cross-sectional studies that recruited patients with PBC and collected data on the smoking status and presence or absence of advanced liver fibrosis for each participant. Odds ratios (OR) with 95 per cent confidence intervals (CI) was desirable for inclusion or sufficient raw data to calculate the same for this association. Adjusted point estimates from each study were extracted and combined together using the generic inverse variance method of DerSimonian and Laird. I 2 statistic, which quantifies the proportion of total variation across studies was used to determine the between-study heterogeneity. Results: Three cross-sectional studies with 544 participants were included. The pooled analysis found a significantly increased risk of advanced liver fibrosis among patients with PBC who were ever-smokers compared to those who were nonsmokers with the pooled OR of 3.00 (95% CI, 1.18-7.65). Statistical heterogeneity was high with I 2 of 89 per cent. Interpretation & conclusions: This meta-analysis found that smoking is associated with a significantly higher risk of advanced liver fibrosis among patients with PBC. Further prospective studies are still required to determine whether this association is causal.