Hepatitis C virus infection and tobacco smoking - joint health effects and implications for treatment of both: A systematic review

Background: Tobacco smoking and hepatitis C virus (HCV) infection cause many diseases independently. The interaction of these conditions on health effects has not been widely studied. There is a paucity of information on addressing tobacco smoking in HCV treatment settings. This review examines the relationship between tobacco smoking and HCV infection and health outcomes and discusses opportunities for treating both conditions. Methods: A systematic review was conducted following the PRISMA 2009 guidelines (Registration No.: CRD42019127771). We searched PubMed, EMBASE, Web of Science, and CINAHL on the health effects of tobacco smoking and HCV infection using keywords and MeSH terms for hepatitis C, tobacco smoking, hepatocellular carcinoma (HCC), chronic obstructive pulmonary disease (COPD), diabetes mellitus (DM), cardiovascular diseases (CVD), and chronic kidney disease (CKD). We used the Newcastle-Ottawa Scale, a measurement tool to assess systematic reviews (AMSTAR-2), and international narrative systematic assessment (INSA) tools to assess the methodological quality of the included studies. Findings: Tobacco smoking and HCV infection share similar underlying risk factors and hence it is unsurprising that tobacco smoking prevalence is higher in people living with HCV (PLHCV) than in the general population. Tobacco smoking and HCV infection have additive or multiplicative interaction to cause HCC, COPD, DM, CVD, and CKD. Anti-HCV direct-acting antiviral (DAA) treatment is highly efficacious and widely accessible in many countries, but untreated tobacco smoking addiction may undermine the achievement of optimal health outcomes possible from HCV treatment. Interpretation: The scale-up of DAA treatment programs globally is an opportunity to address the high prevalence of tobacco smoking in PLHCV by concurrently offering tobacco smoking cessation treatment. Simultaneous initiation of smoking cessation therapy at HCV treatment centres is likely to be cost-effective at maximizing the health gains afforded by DAA treatment. Studies are needed to evaluate the effect of tobacco smoking cessation on the sustained virologic response in DAA treated patients.