Liver cirrhosis and other chronic liver diseases are usually compartmentalized into separate categories based on etiology (e.g., due to alcohol, virus infection, etc.), but it is important to study the intersection of, and possible interactions between, risk factors. The aim of this study is to summarize evidence on the association between alcohol use disorders (AUDs) and decompensated liver cirrhosis and other complications in patients with chronic Hepatitis C virus (HCV) infection. A systematic search of epidemiological studies was conducted using Ovid Medline databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria. Relative Risk estimates were combined using random-effects meta-analyses. The proportion of cases with liver disease progression that could be avoided if no person with a chronic HCV infection had an AUD was estimated using an attributable fraction methodology. A total of 11 studies fulfilled the inclusion criteria, providing data from 286,641 people with chronic HCV infections, of whom 63,931 (22.3%) qualified as having an AUD. Using decompensated liver cirrhosis as the outcome for the main meta-analysis (n = 7 unique studies), an AUD diagnosis was associated with a 3.3-fold risk for progression of liver disease among people with a chronic HCV infection (95% Confidence Interval (CI): 1.8-4.8). In terms of population-attributable fractions, slightly less than 4 out of 10 decompensated liver cirrhosis cases were attributable to an AUD: 35.2% (95% CI: 16.2-47.1%).

For a secondary analyses, all outcomes related to liver disease progression were pooled (i.e., liver deaths or cirrhosis in addition to decompensated liver cirrhosis), which yielded a similar overall effect (n = 13 estimates; OR = 3.7; 95% CI: 2.2-5.3) and a similar attributable fraction (39.3%; 95% CI: 21.9-50.4%). In conclusion, AUDs were frequent in people with chronic HCV infections and contributed to worsening the course of liver disease. Alcohol use and AUDs should be assessed in patients who have liver disease of any etiology, and interventions should be implemented to achieve abstinence or to reduce consumption to the greatest possible extent.