| | Confounders of the Relation between Type of Alcohol and Cardiovascular DiseaseThere have been numerous reports from epidemiologic studies showing that moderate drinkers have lower rates of cardiovascular disease (CVD) than do those who drink heavily or not at all. A number of scientific reports from scientists around the world suggest confounding may play a role in the reported beneficial health effects associated with moderate drinking. Among potentially confounding variables for these reported associations are the frequency of alcohol consumption, drinking pattern (steady or binge drinking), type of beverage, and differences in the pattern of drinking associated with different types of beverages. In some papers, individuals who report primarily wine consumption have been shown to be at lower risk of CVD and total mortality, and there is evidence for greater beneficial effects from more frequent, regular drinking. However, other potential confounders include better cognitive function, higher socioeconomic status, better subjective health, and a healthier diet, including food purchases, all of which are more common in regular drinkers and wine drinkers. Thus, the question of whether the beneficial effects of beverage types differ, with additional benefits for wine, remains unresolved. Introduction  A large number of simple prospective studies have quite consistently shown that alcohol (ethanol) itself has cardioprotective properties and thereby contributes to the descending leg of the U-shaped relationship between alcohol and all-cause mortality 1, 2, 3, 4. A recent longitudinal study has confirmed this by showing that in a randomly selected healthy population, a change in intake over a 5-year period implied an increased risk of cardiovascular disease (CVD) among those who decreased their consumption, and a decreased risk among abstainers who increased their intake of alcohol (5). The effect of alcohol seems relatively short-term and acute when CVD is the outcome, with much longer latency times when it comes to cancer (6). During the past decade, some epidemiological studies have suggested that drinkers of wine have a lower incidence of CVD than drinkers of other types of alcohol 7, 8, 9, 10, 11. It has been shown in some populations that beer, wine, and spirits may also have a differential effect on other health outcomes 8, 12, 13 (Fig. 1). These differences in “effect” on health may be explained by true differences; there are experimental studies to support several plausible biological explanations. Wine contains several components that may contribute to a possible antithrombotic and anticarcinogenic effect, which may exert their action locally in parallel with the possible effect of ethanol. Polyphenolic substances, for example, have been shown to inhibit platelet aggregation. An alternative explanation is confounding. In many countries and cultures there are differences between drinkers of different types of alcohol and these differences may have confounded the results. Drinking Patterns and Other Confounders Among the potentially confounding variables for the reported associations between alcohol intake and health outcomes is drinking pattern, which is defined herein as the frequency of alcohol consumption, divided into steady or binge drinking. Both in large American and Danish cohorts it has been shown that men who drink alcohol more frequently have a lower risk of developing CVD than those who drink less frequently, independent of the amount of intake 14, 15. The findings are less convincing for women (15) (Fig. 2). Several explanations may account for a possible interaction between sex and drinking frequency. One explanation is sex-specific drinking habits, such as drinking with meals. It cannot be excluded that men who drink frequently are more likely to drink with meals, which may contribute to a greater risk reduction when compared with men with less frequent alcohol intake. Other potential confounders include cognitive function, socioeconomic status, subjective health, and dietary habits, since all of these factors have been shown to be associated with intake of different types of beverages 16, 17, 18, 19. In the Copenhagen City Heart Study, conducted on a cohort of Danish men, a strong dose-response relationship was recently found between IQ scores in young adulthood and beverage preferences later in life. Intelligence seemed to correlate strongly in a positive way to a preference for wine. The strength of the association was maintained as the total consumption of wine increased over time in that cohort (18). It is likely that dietary factors need more thorough attention. Some studies have found wine drinkers to have a healthier diet than drinkers of beer or spirits, and variation in diet associated with the preferred drink may explain why wine seems to have an additional beneficial effect on health outcomes. However, self-reported diet and other lifestyle factors may themselves be underreported or overreported. For example, intake of certain food items may be either exaggerated or understated depending on health recommendations. These misclassifications are likely to be associated with educational level, income, and a preference for different alcoholic beverage types. We tested this idea by studying the relationship between the purchase of beer and wine and various other food items. The purpose of the study was to investigate whether wine purchasers buy healthier food items on the whole and thereby have a healthier diet than do beer buyers. The data were collected from sales tickets obtained from supermarkets in Denmark. The results showed that wine buyers tended to buy more olives, fruits, vegetables, poultry, cooking oil, and low-fat products than beer buyers (20). Beer buyers tended to buy precooked dishes, sugar, cold cuts, chips, pork, butter, sausages, lamb, and soft drinks more often than wine buyers (Fig. 3). Generally, both beer and wine buyers shop more frequently on weekends than on other days, but wine buyers are more likely to purchase food items consistent with the Mediterranean diet, whereas beer buyers tend to buy “traditional” food items. In conclusion, the question of whether the beneficial effects of beverage types differ, with additional benefits for wine, remains unresolved. It may still be the drink, but it may also be the drinker. References 1. 1Boffetta P, Garfinkel L. Alcohol drinking and mortality among men enrolled in a American Cancer Society prospective study. Epidemiology. 1990;1:342–348. MEDLINE |
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2. 2Corrao G, Bagnardi V, Zambon A, Arico S. Exploring the dose-response relationship between alcohol consumption and the risk of several alcohol-related conditions: a meta-analysis. Addiction. 1999;94:1551–1573. MEDLINE |
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6. 6Leinoe EB, Hoffmann MH, Kjaersgaard E, Nielsen JD, Bergmann OJ, Klausen TW, et al. Prediction of haemorrhage in the early stage of acute myeloid leukaemia by flow cytometric analysis of platelet function. Br J Haematol. 2005;128:526–532. MEDLINE |
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11. 11Wannamethee SG, Sharper A. Type of alcohol drink and risk of major coronary heart disease events and all-cause mortality. Am J Public Health. 1999;89:685–690. MEDLINE |
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12. 12Grønbæk M, Becker U, Johansen C, Tonnesen H, Jensen G, Sorensen TIA. Population based cohort study of the association between alcohol intake and caner of the upper digestive tract. Br Med J. 1998;317:844–848. 13. 13Pedersen A, Johansen C, Grønbæk M. Relations between amount and type of alcohol and colon and rectal cancer in a Danish population-based cohort study. Gut. 2003;52:861–867. MEDLINE |
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14. 14Mukamal K, Conigrave M, Mittleman M, Camargo C, Stampfer MJ, Willett WC. Roles of drinking pattern and type of alcohol consumed in coronary heart disease in men. N Engl J Med. 2003;348:109–118.
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15. 15Tolstrup J, Jensen MJ, Tjonneland A, Overvad K, Mukamal KJ, Grønbæk M. Prospective study of alcohol drinking patterns and coronary heart disease in women and men. Br Med J. 2006;332:1244–1248. 16. 16Barefoot JC, Grønbæk M, Feaganes JR, McPherson RS, Williams RB, Siegler IC. Alcohol beverage preference, diet, and health habits in the UNC Alumni Heart Study. Am J Clin Nutr. 2002;76:466–472. MEDLINE 17. 17Grønbæk M, Mortensen E, Mygind K, Andersen A, Becker U, Gluud C. Beer, wine, spirits and subjective health. J Epidemiol Community Health. 1999;53:721–724.
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18. 18Frost L, Vestergaard P, Mosekilde L, Mortensen LS. Trends in incidence and mortality in the hospital diagnosis of atrial fibrillation or flutter in Denmark, 1980–1999. Int J Cardiol. 2005;103:78–84. Abstract | Full Text |
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19. 19Tjonneland A, Grønbæk M, Stripp C, Overvad K. Wine intake and diet in a random sample of 48763 Danish men and women. Am J Clin Nutr. 1999;69:49–54. MEDLINE 20. 20Johansen D, Friis K, Skovenborg E, Grønbæk M. Food buying habits of people who buy wine or beer: cross sectional study. BMJ. 2006;332:519–522. From the Centre for Alcohol Research, National Institute of Public Health  Address correspondence to: Morten Grønbæk, MD, Centre for Alcohol Research, National Institute of Public Health, Copenhagen, Denmark.
PII: S1047-2797(07)00006-3 doi:10.1016/j.annepidem.2007.01.004 © 2007 Elsevier Inc. All rights reserved. | |
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