Moderate consumption of alcohol is inversely related with coronary disease, but that dose and its association with mortality is controversial.
The authors of this study therefore carried out a meta-analysis of prospective studies on levels of alcohol consumption and total mortality from thirty-four selected studies on men and women, (a total of 1,015,835 subjects and 94,533 deaths).
Results showed a J-shaped relationship between alcohol and total mortality in both men and women. Consumption of alcohol, up to 4 drinks per day in men and 2 drinks per day in women, was inversely associated with total mortality, with maximum protection being 18% in women and 17% in men.
Higher doses of alcohol were associated with increased mortality. The inverse association in women disappeared at doses lower than in men. When adjusted and unadjusted data were compared, the maximum protection was only reduced from 19% to 16%. The degree of association in men was lower in the United States than in Europe. The authors conclude that low levels of alcohol intake (1-2 drinks per day for women and 2-4 drinks per day for men) are inversely associated with total mortality in both men and women. Their findings, while confirming the hazards of excess drinking, indicate potential windows of alcohol intake that may confer a net beneficial effect of moderate drinking, at least in terms of survival.
Comments by R. Curtis Ellison
This meta-analysis involved a huge number of subjects from 56 independent prospective studies. It confirmed that the relation between alcohol intake and total mortality is J-shaped, with about 16% reduced risk for light drinkers and increased mortality for heavy drinkers.
Several points from this study are worth emphasizing. For men, the risk of mortality was lower for drinkers up to about 3 to 4 drinks per day, but the relative risk crossed the line for women at about 2 drinks/day. This is shown in Fig. 3.A from the article, below, that gives the relative risk (versus non drinkers) of adjusted estimates from the meta-analysis and 99% confidence intervals. While the nadir of the risk for both men and women is around 5 grams/day, or the equivalent of just under _ drink/day, the level at which the relative risk increases above that of non-drinkers is at about 25 g/day for women and 40 g/day for men. The upper 99% confidence interval reaches 35 g/day for women and 45 g/day for men. The authors point out that an under-estimation of intake by subjects (which is generally considered to be the case in epidemiologic studies) would move these values to the right (meaning greater safety for moderate drinking) while over-estimation of intake would move the values to the left.
These data support much earlier research showing that the effects of a given amount of alcohol may be greater in women, probably mainly because of differences in metabolism of alcohol.
A second important point is that, for men, studies in Europe show greater beneficial and less harmful effects than studies in the USA, as illustrated in Figure 3.C.
Here, the relative risk of drinkers exceeds that of non-drinkers at about 30 g/day in studies in the United States but not until almost 65 g/day in studies in Europe. While the reasons for this are not know, it may relate to differences in drinking practices, in that consuming alcohol on a regular basis and with meals is a usual pattern in much of Europe but drinking mainly on the week-end remains more common in the United States. Among women, the differences between studies in the United States and Europe were less marked.
Source: Di Castelnuovo A, et al. Alcohol dosing and total mortality in men and women. An updated meta-analysis of 34 prospective studies. Arch Intern Med 2006;166:2437-2445