Over the past decade several research teams both in the USA and Europe have claimed that a J-shaped curve, as in the case of coronary heart disease, can be seen between alcohol intake and ischaemic stroke. The graph showing the lowest risk of the condition among moderate drinkers, the higher risk showing not only in heavy consumers but also abstainers.

The definition of moderate drinking has lacked clarity as some researchers have focused on daily intake while others have emphasised frequency of consumption. Also a misleading impression of the benefit of moderate drinking can result, as groups categorised as abstainers may have included individuals who had abstained because of poor health. The new data came from a survey designed to clarify the matter.

American Physicians aged 40-84 were enrolled in 1982 in a wide-ranging health study. At that time, the physicians reported no history of stroke, or even symptoms, which might be attributed to a very minor stroke. Other conditions that may also have led to abstention were heart attack, cancer, liver disease and peptic ulcer.

Also recorded were the doctors' drinking habits in terms of drinks of wine, beer or liquor per day, week or month. After 7 years the subjects were asked again and the findings correlated very closely with the original figures, 97% of the participants fell into the light-to-moderate category of 1-7 drinks per week.

From 1982 onwards, every 6 months a questionnaire was sent in which they could record evidence of newly diagnosed conditions, including stroke. Information about deaths and causes was obtained from relatives and confirmed by independent record. All the data was correlated with alcohol intake data in an attempt to see what pattern emerged.

The average follow-up period was just over 12 years, during which 697 strokes occurred.

Results.

Subjects who consumed more than one drink per week were approximately 20% less likely to have a stroke than those who took less than one per week were. When the findings for the two different types of stroke were separated, the reduction in risk for ischaemic stroke was slightly greater than that for strokes in general. No significant relationship was found between alcohol intake and the other much less common type of stroke, which occurs when a blood vessel haemorrhages into the brain.

The protective effect of as little as one drink per week was revealed on closer inspection of different categories of alcohol intake. However, greater consumption, up to one drink per day, did not increase the benefits any further. The investigators conclude that while the findings "may be important for persons who consume alcoholic beverages with low or moderate frequency", no generalisation should be drawn in terms of lifestyle advice.

The investigators point out that heavy drinking is a risk factor for both types of stroke and also cite claims that any overall increase alcohol consumption in a population is likely to be accompanied by a proportionate rise in heavy drinking.

Source:Light-to-Moderate Alcohol Consumption and the Risk of Stroke Among U.S. Male Physicians, New England Journal of Medicine (1999), 341, 1557-64, Berger K., Ajani U.A., Kase C.S., Gaziano J. M., Buring J.E., Glynn R.J.and Hennekens C.H., Division of Preventive medicine, Department of Medicine, Brigham and Women's Hospital; Department of Veterans Affairs Boston Healthcare System; Department of Ambulatory Care and Prevention, Harvard Medical School; Department of Biostatistics, Harvard School of Public Health; and Department of Neurology, Boston University School of Medicine, Boston, MA; Institute of Epidemiology and Social Medicine and Department of Neurology, University of Muenster, Muenster, Germany; Department of Epidemoilogy and Public Health, University of Miami, Miami, USA.