Alcohol and Cardiovascular Disease Risk and Outcomes: Compelling Evidence?
Researchers conducted 2 systematic reviews of the literature to summarize alcohol’s cardiovascular (CV) effects.
The first review identified 84 prospective cohort studies. Compared with not drinking alcohol,
- alcohol consumption was associated with lower risk for mortality from cardiovascular disease (CVD) and coronary heart disease (CHD) (relative risk [RR] for both, 0.75), incident CHD (RR, 0.71), and all-cause mortality (RR, 0.87).
- drinking 5 or more drinks per day was associated with incident stroke (RR, 1.6) and an increase in stroke mortality (RR, 1.4; of borderline significance).
The second review meta-analyzed results of 44 before-after studies (i.e., no alcohol use versus after alcohol use) and crossover studies on fasting plasma biomarkers for CHD risk.
- Alcohol consumption was associated with more favorable levels of 4 of 13 risk markers (high-density lipoprotein cholesterol, apolipoprotein A1, adiponectin, and fibrinogen).
- It was not associated with C reactive protein, plasminogen activator inhibitor 1, tissue plasminogen activator, total or low-density lipoprotein cholesterol, Lp(a) lipoprotein, triglycerides, tumor necrosis factor α, or interleukin 6.
Comments:These reviews suggest alcohol can reduce CVD and identify some possible mechanisms. Systematic reviews, however, cannot overcome limitations in original studies. For example, most of the observational studies measured alcohol consumption then examined outcomes years later—a design that would never be acceptable for study of a pharmacological preventive intervention. And, none can adequately adjust for the large number of relevant confounders (e.g., healthy characteristics of people who choose to drink “moderate” amounts). The authors state that they find the argument for causation compelling, but the evidence seems similar to the effects of estrogens on CVD risk markers and the numerous and consistent observational studies that found hormone replacement to be beneficial that were consistently wrong. Randomized trials may provide the only compelling evidence. Richard Saitz MD, MPH
Ronksley PE, Brien SE, Turner BJ, et al. Association of alcohol consumption with selected cardiovascular disease outcomes: a systematic review and meta-analysis. BMJ. February 22, 2011 (E-pub ahead of print), doi: 10.1136/bmj.d671.Brien SE, Ronksley PE, Turner BJ, et al. Effect of alcohol consumption on biological markers associated with risk of coronary heart disease: systematic review and meta-analysis of interventional studies. BMJ. February 22, 2011 (E-pub ahead of print), doi: 10.1136/bmj.636.