The present publication is from the very large Prospective Urban Rural Epidemiological (PURE) study that focuses especially on middle-income and lower-income countries, for which previous data on the association of alcohol consumption with health outcomes are sparse. Included in this analysis are data from high-income countries (HICs: Sweden and Canada); upper-middle-income countries (UMICs: Argentina, Brazil, Chile, Poland, South Africa and Turkey); lower-middle-income countries (LMICs: China and Columbia); and low-income countries (LICs: India and Zimbabwe). The large majority of the subjects were from lower income countries.
It has long been recognized that, when evaluating the health effects of drinking, it is especially important to evaluate alcohol intake within a particular population, with its specific genetic, lifestyle, environmental, and cultural factors, and not study alcohol in isolation. While the PURE study is a very well-done study, Forum members were concerned that the authors have attempted to answer overall questions about alcohol and health by combining data from such diverse populations. For example, the issue of very different causes of mortality in different populations would lead to very different approaches to improving longevity. There are too many factors associated with health outcomes to attempt to determine the specific alcohol effects when considered in isolation.
The authors tried to adjust for confounders as far as that was possible, but one cannot exclude further confounding, especially as subjects from lower-income countries contained a much larger proportion of smokers than there were in higher-income countries. The authors also point at differences between countries not fully explained by drinking pattern (or other factors); this suggests that further confounding exists. Further, lumping all types of stroke into one category may be hiding associations, especially as lower-income countries might have a higher frequency of cerebral hemorrhages. Similarly, using a single grouping for all cancers may be inadequate. Other limitations of this study include the short duration of follow-up time (4.3 years) and the low number of cases of each outcome.
The Forum concluded that even though the study includes information from many countries, it is not possible from such data to determine net health effects of alcohol consumption that are applicable to people everywhere. Their analytic results cannot be used, as the authors suggest, to “support global health strategies,” although they may surely be useful for developing “national initiatives to reduce harmful alcohol use,” especially for lower-income countries.
Reference: Smyth A, Teo KK, Rangarajan S, O’Donnell M, Zhang X, Rana P, Leong DP, et al. Alcohol consumption and cardiovascular disease, cancer, injury, admission to hospital, and mortality: a prospective cohort study. Lancet 2015. Pre-publication. http://dx.doi.org/10.1016/ S0140-6736(15)00235-4. Online/Comment http://dx.doi.org/10.1016/ S0140-6736(15)00236-6.