Effects of high alcohol intake, alcohol-related symptoms and smoking on mortality.

BACKGROUND AND AIMS: Both high alcohol intake and alcohol dependence increase mortality, and both are associated with smoking. We aimed to compare the associations of quantity of alcohol, number of alcohol-related symptoms and smoking history with all-cause mortality, and to assess symptom count and smoking history as confounders or mediators of the effects of high alcohol intake.

DESIGN: Survival was analysed by Cox regression with sex, body mass index, alcohol intake (overall and by beverage), maximum drinks on any day, alcohol symptom count and smoking status as potential predictors of age at death.

SETTING: Australia.

PARTICIPANTS: Participants were apparently healthy volunteers consisting of 33 593 Australian adult twins and their relatives who completed questionnaires or interviews between 1979 and 2005.

MEASUREMENTS: Data on alcohol use, smoking and occurrence of symptoms related to alcohol use disorders and death records from the Australian National Death Index.

FINDINGS: A total of 3764 participants were matched with deaths occurring within Australia up to July 2014. Individually, alcohol intake [hazard ratio (HR) = 1.0082, 95% confidence interval (CI) = 1.0063-1.0102, per drink per week], beer intake (HR = 1.0159, 95% CI = 1.0123-1.0195, per drink per week), life-time maximum number of drinks in 1 day (HR = 1.0176, 95% CI = 1.0130-1.0221, per drink), symptom count (HR = 1.0867, 95% CI = 1.0633-1.1106, per symptom) and smoking status (HR = 2.82, 95% CI = 2.52-3.16 for smokers of 10+ cigarettes/day versus never-smokers) were each significant predictors of all-cause mortality. After adjustment for the independently significant predictors alcohol symptom count and smoking status, alcohol intake was no longer significant (adjusted HR = 1.0012 per drink per week, 95% CI = 0.9979-1.0145).

CONCLUSIONS: Number of symptoms related to high alcohol intake and tobacco smoking appear to account for the positive association between alcohol consumption and premature mortality.