Interaction between alcohol consumption and positivity for antibodies to hepatitis C virus on the risk of liver cirrhosis: a case-control study. Provincial Group for the Study of Chronic Liver Disease

To assess the risk of developing liver cirrhosis associated with alcohol consumption, HBV and HCV infection markers, we carried out a case-control study involving 115 patients admitted to the medical departments of the general hospitals in the province of L'Aquila (Abruzzo, Italy) who received for the first time the diagnosis of liver cirrhosis, and 167 controls randomly selected among patients admitted to the same hospitals as the cases. Alcohol intake was measured in all 282 subjects using an already validated standardized questionnaire, and expressed as mean lifetime daily alcohol intake in grams. The mean lifetime daily alcohol intake showed a dose-dependent effect on the risk of cirrhosis: the relative risk significantly rose to 3.8 (95% CI: 2.0-7.3) for a mean daily intake of > or = 101 g alcohol; for HBsAg positivity the relative risk of cirrhosis was 23.0 (95% CI: 4.9-107.8) and for anti-HCV positivity it was 8.7 (95% CI: 4.3-17.6). After applying a multiple logistic regression analysis in a multivariate model including mean lifetime alcohol intake and anti-HCV status, both variables were significantly associated with the risk of cirrhosis (relative risks = 5.3-95% CI: 2.3-12.2 and 9.9-95% CI: 4.4-22.0, respectively). The combination of these two variables was found to fit an additive--but not multiplicative--model relative to the risk of cirrhosis: furthermore, the interaction of the anti-HCV status with the presence or absence of cirrhosis did not result in a significant source of variability for the mean lifetime daily alcohol intake