The Interheart Study is a large international collaborative project which follows individuals with a first heart attack (myocardial infarction) and compares their age- and sex-matched controls across 52 countries in Asia, Europe, the Middle East, Africa, Australia, North and South America.

Included are nations with very divergent lifestyles, religions, degrees of development, and drinking habits. The authors attempt to provide a “world-wide” overview of the relation of alcohol consumption to the risk of myocardial infarction (MI).

However, they were forced to use a case-control design, a type of study with many opportunities for bias and one that prevents determination of a causal relation. Further, the lack of detailed data on the amount of alcohol consumed by individuals weakens their results.

While the authors state that their study shows that low levels of alcohol use are associated with a moderate reduction in the risk of MI, they point out differences in results in different countries. Forum members considered that these large differences severely limit their ability to use such a dataset to provide overall conclusions on alcohol and MI. For example, only 1% of the non-drinkers in this study came from Western Europe and 1% from North America, while more than 70% of the non-drinkers came from the Middle East or Asia.

With such diversity (e.g., almost all the abstainers were from one area), it is not possible to adequately “adjust” for such regional differences in analysis. 

The authors also studied how alcohol consumption shortly prior to (in the 24 hours before) the occurrence of a MI relate to the short-term risk of MI. While their results show an increased risk for heavy drinking immediately prior to an MI, they had analytic problems, stating: “Thus, there remains uncertainty over the risk of MI in the period immediately following alcohol intake.”

Previous large prospective cohort studies (a type of epidemiologic study that decreases the risk of recall bias regarding alcohol intake and certain types of confounding) have clearly shown an inverse relation (or protective effect) between moderate alcohol consumption and heart attack. 

Most of the previous studies have provided much more detailed data on alcohol exposure than did the present study. The authors realised many of these problems, and warn against using their results to make overall conclusions about the association between alcohol and MI from their paper.

“The associations observed between alcohol use and MI may be accounted for by unmeasured confounders such as genetic differences between populations, variation in alcohol type or preparation, and heterogeneity of social context," they state. "The present analysis should therefore prompt further research to clarify the nature of the association between alcohol use and MI.”

To read the full critique, click here.

These critiques are published with the permission of The ISFAR.