The large European Prospective Investigation into Cancer and Nutrition Study (EPIC) has released a new analysis of the relation of alcohol consumption to mortality. The study concluded that alcohol use was positively associated with overall mortality, alcohol-related cancers, and violent death and injuries, but marginally to cardiovascular disease, and that absolute risks of death observed in EPIC suggest that alcohol is an important determinant of total mortality.
There is no question that heavy alcohol consumption, especially when associated with smoking, increases the risk of a number of upper aero-digestive cancers that are commonly referred to as “alcohol-related cancers.” In the present study, the authors have also included in this group a number of other cancers that may be related less directly to the effects of alcohol; these include colorectal cancer and female breast cancer which, because they are so much more common, make up the large majority of cancers “related to alcohol.” Forum members consider the EPIC study to be an important source of data on cancer, but had a number of questions about the analysis and especially about the conclusions of the authors.
Major weaknesses of the study are that an assessment of alcohol intake was obtained only at a baseline visit, with no further assessments during a follow-up period averaging 12 years, and especially, no information was available on the pattern of drinking of subjects (e.g., regular moderate versus binge drinking). Further, Forum members noted that there was no discussion of the effects of under-reporting of alcohol, which has been shown to markedly affect health effects of alcohol intake in epidemiologic studies. In fact, recent large studies show that most of the cases of cancer that appear to relate to “light-to-moderate drinking” actually relate to underreporting of consumption by subjects who are found, from other collected medical data, to be heavy users or abusers of alcohol.
The authors focus on “extreme drinkers,” which consist of women who consume (≥30 g/day) or men who consume ≥60 g/day. They do not point out that only 2.4% of the women in this study consumed at this level, and little attention is given to the fact that almost all of the women were non-drinkers or light-moderate drinkers. From the data presented in the paper, there is a clear U-shaped curve among women: the highest risks for total mortality were in the abstainers (a 26% increase over the referent group of light drinkers) and the very small number of women in the highest drinking category (a 27% increase).
For men, 8.2% were in the highest drinking category, reporting an average consumption of ≥ 60 g/d (5 – 6 typical drinks). For men, there was generally a U-shaped curve, with lower death rates for light to moderate drinkers. However, the heaviest drinkers had the highest risk of death for overall mortality and for deaths from cancers and other causes of death. For both men and women, at every level of drinking, smokers had an increased risk of death in comparison with non-smokers.
Some reviewers were also concerned about the unusual categorization of alcohol intake used in the study. Referring to subjects reporting 0.1 – 4.9 g/day as “moderate drinkers” is a strange designation for an alcohol intake that in most other studies would be named as light or very modest, and may lead to confusion in interpreting results. (Most studies would define 5 – 14.9 g/day as light to moderate drinkers, and this group is not given a name in this study).
Overall, this study tends to show a U-shaped relation between alcohol consumption and mortality. The data presented focus primarily on the highest categories of drinking, levels that are well known to relate to many diseases and mortality. For truly light-to-moderate consumption, however, there is overwhelming epidemiologic data that such drinking relates to lower mortality risks, and the present study does not contradict such an association.
Reference: Ferrari P, Licaj I, Muller DC, et al (36 other authors). Lifetime alcohol use and overall and cause-specific mortality in the European Prospective Investigation into Cancer and nutrition (EPIC) study. Pre-publication; BMJ Open 2014;4:e005245. doi:10.1136/bmjopen-2014-005245