Population studies have shown that moderate drinkers tend to have lowerrates of heart disease but higher rates of bleeding-type strokes thanabstainers. A potential mediator of these two contrasting effects ofalcohol may be platelet function. A study in the October issue of Alcoholism: Clinical & Experimental Researchconfirms that moderate drinking has effects on blood coagulation --primarily as a "blood thinner" -- which can have both positive andnegative effects.
"The contrasting effects of alcohol are similar to the effects ofblood thinners like aspirin, which clearly prevent heart attacks but atthe expense of some additional bleeding strokes," said Kenneth J.Mukamal, an internist at Beth Israel Deaconess Medical Center andcorresponding author for the study. "Acting as a blood thinner makessense, because heart attacks are caused by blood clots that form inclogged arteries, and blood thinners can hasten bleeding from injuredarteries. Based on these findings, we speculated that moderate drinkingwould also act as a blood thinner."
Mukamal added that previous research had shown that moderatedrinkers tend to have "less sticky" platelets than abstainers, meaningthat fewer blood elements cluster to form blood clots. "Yet no onebefore had looked at whether alcohol affects how easily platelets areactivated," he said. "This is important because activated platelets aremuch stickier than normal ones."
In 1971, a total of 5,124 men and women enrolled in theFramingham Offspring Study of risk factors for cardiovascular disease-- the sons and daughters of participants in the original FraminghamHeart Study. Participants have been examined and interviewed every fouryears since 1971, except for an eight-year interval between the firstand second visits. This study uses data collected from 3,798 of thoseparticipants, examined between April 1, 1991 and March 1, 1994 (thefifth examination cycle); eventually analyzing data provided by a totalof 1,037 participants (460 men and 577 women) for platelet activationand 2,013 participants (879 men and 1,134 women) for plateletaggregation.
"We found that among both men and women, an intake of three tosix drinks per week or more was linked to lower levels of stickinessmeasured by aggregability," said Mukamal. "Among the men, we also foundthat alcohol intake was linked to lower levels of platelet activation.Together, these findings -- identify moderate drinking as a potentialblood thinner." Mukamal added that the minor differences found betweenthe men and women were more likely due to statistical issues than toany clear gender differences.
"Our findings add to a large body of evidence showing thatmoderate drinking has effects on blood coagulation, which may have bothgood and bad effects, but now identify a new avenue by which thiseffect may occur," said Mukamal. "By themselves, these findings havemore importance for understanding risk factors for vascular diseasethan any clinical relevance, and should not be used by people as anyreason to begin drinking."
The next step for Mukamal and his colleagues is to evaluatethese findings in other populations. "Heart attacks far outnumberbleeding-type strokes in the United States," he said, "but in somecountries such as Japan, they have much higher rates of bleedingstrokes and lower rates of heart attacks than we do, which is perhapsrelated to dietary differences."
Alcoholism: Clinical & Experimental Research (ACER) isthe official journal of the Research Society on Alcoholism and theInternational Society for Biomedical Research on Alcoholism. Co-authorsof the ACER paper, "Alcohol Consumption and Platelet Activation andAggregation among Women and Men: The Framingham Offspring Study," were:Joseph M. Massaro and Ralph B. D'Agostino of the Department ofMathematics and Statistics at Boston University; Kenneth A. Ault of theMaine Medical Center Research Institute in Scarborough; Murray A.Mittleman of the Department of Medicine at the Beth Israel DeaconessMedical Center in Boston; Patrice A. Sutherland, Izabella Lipinska andDaniel Levy of the National Heart, Lung, and Blood Institute inFramingham, Massachusetts; and Geoffrey H. Tofler of the Division ofCardiology at Royal North Shore Hospital in Sydney, Australia. Thestudy was funded by the National Institute on Alcohol Abuse andAlcoholism and the National Heart, Lung, and Blood Institute.
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