Separate and joint effects of alcohol and smoking on the risks of cirrhosis and gallbladder disease in middle-aged women.
Liu B., Balkwill A., Roddam A., Brown A., Beral V., Million Women Study Collaborators None.
The separate and joint effects of alcohol and smoking on incidences of liver cirrhosis and gallbladder disease were examined in a prospective study of 1,290,413 United Kingdom women (mean age, 56 years) recruited during 1996-2001. After a mean follow-up of 6.1 years (1996-2005), incidence rates of cirrhosis and gallbladder disease were 1.3 per 1,000 persons (n = 2,105) and 15 per 1,000 persons (n = 23,989), respectively, over 5 years. Cirrhosis risk increased with increasing alcohol consumption, while the risk of gallbladder disease decreased (P(trend) < 0.0001 for each). Comparing women who drank > or =15 units/week with those who drank 1-2 units/week, the relative risk was 4.32 (95% confidence interval (CI): 3.71, 5.03)) for cirrhosis and 0.59 (95% CI: 0.55, 0.64) for gallbladder disease. Increasing numbers of cigarettes smoked daily increased the risk of both conditions (P(trend) < 0.0001 for each). Comparing current smokers of > or =20 cigarettes/day with never smokers, the relative risk was 3.76 (95% CI: 3.25, 4.34) for cirrhosis and 1.29 (95% CI: 1.22, 1.37) for gallbladder disease. Effects of alcohol and smoking were more than multiplicative for cirrhosis (P(interaction) = 0.02) but not for gallbladder disease (P(interaction) = 0.4). Findings indicate that alcohol and smoking affect the risks of the 2 conditions in different ways. For cirrhosis, alcohol and smoking separately increase risk, and their joint effects are particularly hazardous. For gallbladder disease, alcohol reduces risk and smoking results in a small risk increase.