THE EFFECT OF DRINKING COFFEE AND SMOKING CIGARETTES ON THE RISK OF CIRRHOSIS ASSOCIATED WITH ALCOHOL-CONSUMPTION - A CASE-CONTROL STUDY

In order to assess the interaction between alcohol intake, tobacco smoking and coffee consumption in determining the risk of liver cirrhosis we carried out a hospital-based case-control study involving 115 patients at their first diagnosis of cirrhosis and 167 control patients consecutively enrolled in the General Hospitals of the Province of L'Aquila (Central Italy), The mean life-time daily alcohol intake (as g ethanol consumed daily) was measured by direct patient interviews, whose reproducibility was > 0.80 and similar for cases and controls, as checked by interviewing the relatives of a sample of 50 cases and 73 controls. During the same patient's interview we also measured the mean consumption of coffee (daily number of cups of filtered coffee) and tobacco (life-time daily number of cigarettes smoked). A dose-effect relationship on the risk of cirrhosis was present both for alcohol intake - for which the risk was significantly increased above 100 g of daily intake - and for cigarette consumption, The latter did not however improve the goodness-of-fit of a logistic regression model including alcohol intake as covariate. By contrast, coffee consumption had a protective effect on the risk of cirrhosis and significantly improved the goodness-of-fit of such a model, Abstaining from coffee consumption determined both a significantly increased risk of cirrhosis, even for daily alcohol intake below 100 g, and a multiplicative effect with alcohol intake on this risk. In patients drinking greater than or equal to 101 g ethanol daily the relative risk increased from 5.5 (95% confidence interval: 1.4-22.0) for coffee consumers to 10.8 (95% confidence interval: 1.3-58.1) for coffee abstainers. We conclude that: (1) tobacco smoking is likely to be a faint risk factor for cirrhosis, and studies on wider patients series should be performed for confirmation; (2) coffee drinking is associated with a reduced risk of cirrhosis. Whether coffee contains some hitherto unknown protective substances, or is just a marker of other life-style or dietary protective factors, deserves further clarification.