The purpose a study by K. Mukamal and colleagues was to quantify the relation between alcohol consumption and cardiovascular and total mortality in patients with a history of cardiovascular events. The authors state that regular, moderate alcohol consumption by healthy people is associated with lower cardiovascular and all-cause mortality, but no extensive meta-analysis is presently available on the possible association of alcohol consumption with secondary events in patients with cardiovascular disease. The authors retrieved articles through October 2009 by search in PubMed and EMBASE. Fifty-four publications were identified, but only 8 were selected for their analyses, including 16,351 patients with a history of cardiovascular disease. Secondary events were cardiovascular or all-cause mortality. All selected studies were prospective. Data were pooled with a weighted, least-squares regression analysis of second-order fractional polynomial models.
The meta-analysis on cardiovascular mortality showed a J-shaped pooled curve with a significant maximal protection (average 22%) by alcohol at approximately 26 g/day. In the meta-analysis on mortality for any cause, J-shaped pooled curves were observed in the overall analysis (average maximal protection of 18% in the range of 5 to 10 g/day) and in all subgroups according to either the type of patients or the characteristics of the studies. The authors conclude that in patients with cardiovascular disease, light to moderate alcohol consumption (5 to 25 g/day) was significantly associated with a lower incidence of cardiovascular and all-cause mortality.
Professor R Curtis Ellison comments: This meta-analysis supports separate reports from earlier studies showing that subjects who already have evidence of cardiovascular disease have better prognosis if they consume some alcohol after developing clinical disease. In reviewing 8 papers with a total of 16,351 patients with a history of cardiovascular disease, reduced mortality was found for consumers of alcohol in comparison with non-drinkers. While the authors suggest a “J-shaped curve,” the estimated risk of death remained lower for consumers of up to about 3 typical drinks/day than it was for abstainers.
This is a very well-done, complete analysis. There was no evidence of publication bias. Potential weaknesses are that the assessment of alcohol intake for 3 studies was obtained shortly after a myocardial infarction (“a few days after the primary event”); for the other 5 studies, alcohol intake was assessed “more than 2 months after the primary event,” which may be preferable for assessing long-term drinking after an event. However, in sensitivity analyses, the estimates of effect of alcohol were the same for the two groups.
In 2 studies, former drinkers were included in the reference group, and in 3 studies it was not stated whether or not they were included. The estimates of effect were greater (47% maximal protection, versus 22-26% reduction overall) among studies not including former drinkers.
The overall association between alcohol consumption and cardiovascular mortality is shown in the figure below, from the paper. It suggests that the lowest relative risk of cardiovascular death (“maximal protection”) could be seen in subjects reporting as little as 5 grams of alcohol per day, the equivalent of only about 2 _ to 3 drinks/week. However, the relative risk (RR) of cardiovascular death remains lower than that of non-drinkers at all levels of alcohol intake; the 95% percentile estimate crosses that of non-drinkers at about 26 grams of alcohol/day (just over 2 typical drinks by US standards).
Pooled curves of relative risk of cardiovascular mortality and alcohol intake, extracted from 7 independent relationships using fixed (solid lines) and random (dotted lines) models. RR = relative risk; 95% CI- = lower value of confidence interval; 95% CI+ = upper value of confidence interval.
Estimates of the association between alcohol and total mortality were very similar, with “maximal protection” of 18-20% at between 5-10 grams/day; the estimated relative risk remained lower than that of non-drinkers throughout the range of alcohol intake, with the upper 95% percentile reaching the risk of non-drinkers at about 24 grams/day.
Source: Mukamal KJ, Chen CM, Rao SR and Breslow RA. Alcohol consumption and cardiovascular mortality among US adults, 1987 to 2002.J Am Coll Cardiol 2010;55:1328-1335.