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Friday, February 3, 2012

Critique 069: Little effect of binge drinking on heart disease or mortality among moderate drinkers in Denmark

Skov-Ettrup LS, Eliasen M, Ekholm O, Grønbaek M, Tolstrup JS. Binge drinking, drinking frequency, and risk of ischaemic heart disease: A population-based cohort study. Scandinavian Journal of Public Health 2011;39:880–887.

Comments on study: This appears to be a well-done population–based study with good follow up and excellent ascertainment of outcomes: IHD and all-cause mortality. This was made possible by the unique civil registry number allocated to each Danish citizen at birth. This number is used in any sort of business with the authorities such as tax, social security, and health, and a social security card with the number must be presented with any contact with the national health system – a failsafe method of securing exact follow-up of all diagnoses or death.

The assessments of alcohol were based on consumption in the week prior to the examination, and binge drinking was defined as more than 5 drinks/occasion. Given that the assessment was from only one week, data were not available to judge whether or not binge-drinking episodes occurred rarely or regularly.

Data were available on the usual covariates related to IHD: smoking, education, physical activity, BMI, and self-reported hypertension and diabetes. There was a strong correlation between binge drinking and the total amount of alcohol consumed, but the authors controlled for total alcohol intake when comparing binge and non-binge drinkers.

When comparing outcomes in binge vs. non-binge drinkers, the analyses were restricted to subjects in the “light-to-moderate” categories. Here, there were no significant differences noted between subjects who binged and those who did not. In all comparisons, the relative risk of IHD and all-cause mortality was higher for non-drinkers than for all categories of drinkers.

When relating frequency of drinking (the number of days of the week when subjects consumed alcohol) to IHD and total mortality, all subjects (not just the light-to-moderate drinkers) were included. Here, again, there were no significant differences in outcomes comparing people consuming alcohol on 1-2, 3-4, 5-6, or 7 days/week (although , once again, the highest risk was always among the non-drinkers). These results differ from those of Mukamal et al1 and Tolstrup et al,2 studies showing that frequency of consumption was a key determinant of health outcomes.

Thus, these findings do not show differences in effects of binge vs. non-binge drinking in terms of IHD or mortality. Further, the study does not show a significant effect according to the number of days per week that subjects consumed alcohol. As one reviewer stated: “The present paper suggests that, within the group of persons following sensible drinking limits of weekly amount of alcohol intake, there does not appear to be adverse effects on the heart when not following the recommendation to avoid having more than five drinks on a single occasion.”

Specific comments on the results of the present study: As a Forum reviewer commented: “The sensible drinking limits of up to 21 drinks/week for men or up to 14 drinks/week for women (1 drink = 12 grams of alcohol) proposed by the Danish National Board of Health are well known in Denmark. It is estimated that, overall, 20% of the population over 16 years of age drink in excess of the proposed drinking limits.3 However, by limiting the study of the effect of binge drinking to subjects who follow the weekly drinking limits (83.7% of the male and 90.4% of the female participants), you have restricted the analysis of binge drinking effects to a population of genuine moderate drinkers.” If binge drinking among all drinkers were evaluated, the results may well have been different.

In the present analyses, a very high percentage of the “light-to-moderate drinkers” reported binge drinking: up to 61% of men in the 14-21 drinks/week category and 35% of the women in the 7-14 drinks/week category. The median number of drinks on a binge was 9 for men and 7 for women. Despite reporting binge drinking, the overall average intake of the subjects in these analyses remained in the light-to-moderate category. Hence, although they reported binge drinking on at least one occasion in the preceding week, they were not overall heavy drinkers.

As one reviewer commented, “The combination of moderate drinking with occasional parties with intake of >5 drinks is a normal pattern of drinking in Denmark. It is assumed that many were in the habit of sharing some bottles of wine with friends on a Saturday evening and then drink very little during work days, while others prefer the daily glass of wine or beer with their meals. However, they would be very similar in other choices of lifestyle.” While the type of beverage consumed was not reported in this paper, a reviewer comments: “Based on data from earlier reports from the Danish National Cohort Study. you would expect that most of the female participants are wine drinkers and that many of the moderate male consumers also prefer wine.” Previous studies from Copenhagen have shown better health outcomes for wine drinkers than for consumers of other beverages.4 In this study, non-drinkers tended to have lower levels of education than the moderate drinkers, as has been found commonly in other studies. > > > > Read More