This meta-analysis is from authors who in the past have tended to argue that the demonstrated inverse association between moderate alcohol consumption and ischemic heart disease (IHD) shown in most studies is due to confounding by other lifestyle factors. However, in this paper, they come to the conclusion (in their words): “Results from our quantitative meta-analysis showed that drinkers with average intake of < 30 g/day and no episodic heavy drinking had the lowest IHD risk (relative risk = 0.64, 95% confidence interval 0.53 to 0.71). Drinkers with episodic heavy drinking occasions had a risk similar to lifetime abstainers (relative risk = 1.12, 95% confidence interval 0.91 to 1.37).”
The conclusions of the authors thus not only support a “J-shaped” curve for alcohol consumption and IHD but provide additional support suggesting that the effect may be causal, i.e., related to the alcohol consumption and not to other associated lifestyle factors. They state: “For drinkers having one to two drinks per drinking day without episodic heavy drinking, there is substantial and consistent evidence from epidemiological and short-term experimental studies for a beneficial association with IHD risk when compared to lifetime abstainers. The alcohol-IHD relationship fulfills all criteria for a causal association proposed by Hill.
” It is clear from epidemiologic studies that moderate drinkers may exhibit moderation in other lifestyle factors (such as not smoking, eating a healthy diet, etc.). Indeed, there is aggregation of healthy lifestyle factors that must be considered when judging how a single factor (such as moderate drinking) relates to disease outcomes. This meta-analysis suggests that other lifestyle factors do not explain the lower risk of IHD found to occur among moderate drinkers. In fact, increasingly, moderate drinking is found to be an independent (and rather important) lifestyle factor that lowers the risk of cardiovascular disease, regardless of other factors. Such protection is not seen when drinking is more than moderate, defined in this paper as an average of 30 grams or more of alcohol per day, the equivalent of about 2 ½ to 3 typical drinks. Reference: Roerecke M, Rehm J. Alcohol consumption, drinking patterns, and ischemic heart disease: a narrative review of meta-analyses and a systematic review and meta-analysis of the impact of heavy drinking occasions on risk for moderate drinkers. BMC Medicine 2014;12:182.