Indeed, the combination of heavy drinking and smoking is particularly harmful. When considering death as the outcome, however, we can simply look at total, or all-cause, mortality to judge the net effects of varying levels of alcohol consumption. All of the studies show that the relative risk of dying from any cause is lower for individuals in at least one category of alcohol consumption than for individuals consuming no alcohol. While the changes were not always statistically significant for each category in each study, the general pattern is very clear. In each of these studies, moderate drinkers had lower death rates than even lifetime abstainers.
Results are the same when only healthy abstainers are included in the non-drinking category.
In reviewing the results of the studies summarized above, two things become clear. First, individuals who reported that they consumed small to moderate amounts of alcohol had lower death rates than non-drinkers. Thus, on the average, the lives of moderate drinkers were prolonged. Therefore, on the average, the lives of heavy drinkers were shortened. It is always difficult to prove scientifically that some factor that is associated with an effect causes that effect.