In our present analysis, we found that alcohol consumption could strengthen the harmful effect from cigarette smoking. Our estimate indicate that compared with the nonsmoker and non-smoker, those who both smoke and drink could have 75% higher risk of death or 112% more likely to die early. We have also indicated that women are likely to have higher risk of all-cause mortality or premature death from the combine effect of tobacco smoke and drink use than men.
Alcohol use has been reported to increase risk of all-cause mortality; however this is generally found to be varied by the amount consumed with a U or J shape being reported. This usually indicated as a lower overall mortality among subject with light to moderate drinking while a higher rate of death among those heavy drinkers(9, 10). However, A study from a large cohort showed that the beneficial effect from the light and moderate alcohol use was offset by cigarette smoke and the risk of total mortality increase with the smoking intensity from 0.8 (95% CI: 0.6, 1.0) for non-smoker to 1.0 (0.9, 1.2) for moderate smokers and 1.4 (95% CI: 1.2, 1.7) for heavy smokers(18). The negative combined effect from smoking and drinking was also reported in other studies(19, 20). Our study was consistent with these findings in general and found that the highest risk was observed among those who both smoke and drink alcohol.
Premature death of a middle-aged person is often devastating to a household and is often associated with decreased income, and mortality in the affected families. Identification of the associated risk is crucial to health planning and policy development(21). In our study, we also tried to explore the adverse association of this synergy effect of cigarette smoking and alcohol consumption with premature death. Consistent with the results for all-cause mortality, we found that, compared with non-smoker and non-drinker, smoker and drinker was significantly associated with early death, despite of the non-significance among subgroup by gender due to the small sample size.
It is noteworthy that the gender difference was found in both all-cause mortality and premature death. It has been noted that women smokers and/or drinker are more likely to have greater mortality risk. This phenomena has been reported in previous publications(1, 4, 9, 19, 22, 23) assessing smoking or drink risk, even among those with existing diseases, such as diabetes (24). The mechanisms underlying the sex difference in mortality may be attribute to their biological or related to differences in smoking behaviour between men and women. It seems that men are likely to be exposed more risks than women, which may confer the risk from smoke or drink use. This can be told from our data. In our study, we found that 52.7% of men were both cigarette smokers and alcohol drinkers, whereas, only 2.19% was found in women.
Several limitations of the study should be mentioned. First, due to the limited information from this public database, further analysis by drink amount or the cause of death, such as CVD mortality or cancer mortality are not available. Several studies have shown that the effect of alcohol consumption on mortality is generally found to depend on the amount consumed and presented differently by cause-specific mortality. However, this was argued by other studies suggesting that the nonlinear relationship is explained by the study design or selected bias across age-sex strata(11, 12). Second, this study is an ongoing study and the follow-up period is relative short. Thus, the statistical power is limited for subgroup analysis by gender. Third, as date of death was only released for data of 2013 follow-up survey, information on age of death and premature death can only be obtained for this survey.
In summary, our present analysis indicated that alcohol consumption could further increase the risk of total death or premature death from smoking. Further studies are needed to confirm the higher risk of death from joint effect of smoking and drink among female population.