Page last updated: Tuesday, june 08, 2010
Alcohol and cardiovascular mortality - Common sense and scientific truth

The aim of a study by A Klatsky et al. was to determine the association of alcohol consumption and cardiovascular mortality in the US population.  The authors state that alcohol consumption has been associated with a lower risk of cardiovascular disease (CVD) in cohort studies, but this association has not been prospectively examined in large, detailed, representative samples of the US population.  They analyzed 9 iterations of the National Health Interview Survey, an annual survey of a nationally representative sample of US adults between 1987 and 2000.  Exposures of interest included usual volume, frequency, and quantity of alcohol consumption and binge drinking.  Mortality was ascertained through linkage to the National Death Index through 2002.  Relative risks were derived from random-effects meta-analyses of weighted, multivariable-adjusted hazard ratios for cardiovascular mortality from individual survey administrations.
Results showed that light and moderate volumes of alcohol consumption were inversely associated with cardiovascular mortality.  Compared with lifetime abstainers, summary relative risks were 0.95 (95% confidence interval [CI]: 0.88 to 1.02) among lifetime infrequent drinkers, 1.02 (95% CI: 0.94 to 1.11) among former drinkers, 0.69 (95% CI: 0.59 to 0.82) among light drinkers, 0.62 (95% CI: 0.50 to 0.77) among moderate drinkers, and 0.95 (95% CI: 0.82 to 1.10) among heavy drinkers. The magnitude of lower risk was similar in subgroups of sex, age, or baseline health status. There was no simple relation of drinking pattern with risk, but risk was consistently higher among those who consumed ≥3 compared with 2  drinks/drinking day.  The authors conclude that in 9 nationally representative samples of US adults, light and moderate alcohol consumption were inversely associated with CVD mortality, even when compared with lifetime abstainers, but consumption above recommended limits was not.
Professor R Curtis Elllison comments:  The importance of this study is that it reflects the population of the United States over a long period of time and is based on more than 10,000 deaths from CVD.  In Table 2 from the paper, below, it can be seen that the multivariable-adjusted hazard ratio estimates for “light” drinking and “moderate” drinking were 31% and 38% lower, respectively, than for the referent group consisting of lifetime abstainers. 
It is interesting that very little difference in CVD mortality was noted between “never drinkers” and “lifelong infrequent drinkers, “former drinkers,” or even “heavy” drinkers.  Further, the investigators found little effect from reported “binge drinking” in this group of subjects.  The key results are the markedly lower risk of cardiovascular death for current drinkers of light to moderate amounts.  While the hazard ratios for CVD death were closer to 1 for minority populations, the authors reported that “light and moderate drinking were associated with significantly lower risk even among minority participants.”
The authors conclude that these findings indicate that “the inverse associations of light and moderate drinking with risk of CVD mortality are robust with respect to the choice of referent category.”   Further, these data are based on population-based samples, and we agree with the authors that their results “provide some of the strongest evidence to date that the observed associations can be generalised to the US population and are not limited to intensively monitored cohorts of volunteers.” 
Accompanying Editorial:  In an excellent, well-balanced accompanying editorial, Arthur Klatsky states that the current study “adds to the case that the inverse relationship of light–moderate drinking to CV mortality is scientifically valid.  One important consideration is the use of a national sample. This aspect contributes strength to the scientific validity of the data by countering the argument that data in narrower study populations might not be generalizable.  Another important strength is directly relevant to the much-debated issue of the most appropriate reference group.  In the present report there is little relationship of CV death to past or infrequent drinking.  If acknowledged past drinkers are not at increased risk, it is less likely that misclassification of others as lifelong abstainers is a factor in results.”  Klatsky adds that, overall, “recent observational population studies consistently show lower risk among lighter drinkers than abstainers for atherothrombotic vascular disease.”  Points favouring a causal protective effect of moderate alcohol drinking include “proper time sequence, consistency in diverse healthy or unhealthy populations, plausible biological mechanisms, relative specificity for atherothrombotic conditions, controlled trial data for surrogate end points, and weakness of data supporting alternative explanations.” 
Regarding physicians having to make recommendations based on observational data, rather than on randomised controlled trials, Klatsky states: “The risks of moderate drinking differ by sex, age, personal history, and family history.  As is often the case in medical practice, advice about lifestyle must be based on something less than certainty.  There is no substitute for balanced judgment by a knowledgeable, objective health professional.  What is required is a synthesis of common sense and the best available scientific facts.”
Source: Klatsky AL. Alcohol and cardiovascular mortality.  Common sense and scientific truth. J Am Coll Cardiol 2010;55;1336–1338.

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