While heavy alcohol consumption appears to increase risk of all
types of strokes, scientists have begun to acknowledge the potentially
protective effect of moderate alcohol consumption. Recent months
have seen the publication of many new studies. Results have been
consistent enough for at least one organization, the National Stroke Association (NSA), to include some favorable information about alcohol and stroke
in its prevention guidelines.
One of the difficulties in advising about alcohol and stroke is
that different types of stroke have slightly different relationships
with alcohol intake. While the evidence on moderate intake and
the most common form of stroke, ischemic stroke, has been almost
entirely favorable, some studies have found an increased risk
for the less common hemorrhagic stroke.
In a "Multidisciplinary Consensus Statement" from the NSA published this year in JAMA, researchers describe some of these differences, noting that
"there is evidence that light to moderate drinking may have beneficial
effects by increasing high-density lipoprotein cholesterol levels
and decreasing platelet aggregation and fibrinogen levels. They advise, "Since some ingestion of alcohol, perhaps up to 2 drinks per day,
may actually help reduce the risk of stroke, drinking in moderation
should be recommended for those who drink alcohol and have no
health contraindications to alcohol use. However, those who do
not customarily drink should not be encouraged to do so."
In 1998, NSA’s Prevention Advisory Board stated, "Studies now show that drinking up to two drinks per day can reduce
your risk for stroke by about half. More alcohol than this each day
can increase your risk for stroke by as much as three times and
also can lead to liver disease, accidents and more... if you don’t drink, don’t start!" The acknowledgment of recent scientific developments by organizations
such as the NSA reflect considerable changes in public health attitudes toward
alcohol.
In the past year, new studies from Spain, Australia, United States
and Denmark have reported a favorable association between low-to-moderate
drinking and a reduced risk of stroke. In the Journal of Clinical Epidemiology,Spanish re-searchers investigated the relationship between alcohol
consumption and stroke in a case-control study. They found a J-shaped
relation between alcohol and all stroke combined, writing, "We found that consumption of less than 30 g/day of alcohol was
protective against all stroke types combined." Specifically moderate intake was most protective against cerebral
infarction and cortical infarction, and heavy consumption of over
140 g/day increased risk of all types of stroke.
Despite past evidence that has been contradictory, the Spanish
researchers found no increased risk for hemorrhagic stroke among
moderate drinkers. Interestingly, an Australian study published
this year in Epidemiology investigated hemorrhagic stroke directly, with researchers analyzing
the relation between levels of all alcohol types and risk of intracerebral
hemorrhage (ICH), stroke caused by bleeding in the brain. When
compared to non-drinkers, moderate drinkers of all alcohol beverages
had a 40 percent reduction in risk of ICH, though heavy drinkers
had a substantial increase in risk. The researchers noted a 70
per-cent reduction for male wine drinkers and a 50 percent reduction
for female wine drinkers, as compared to "never drinkers."
In a well-publicized study by Sacco et al published in JAMA in 1999, light or occasional alcohol consumption was associated
with lowered ischemic stroke (responsible for 80 percent of all
strokes) risk by up to 62 percent compared to non-drinkers in
a multi-ethnic New York City population. For people who consumed
up to two alcoholic drinks per day, stroke risk was 45 percent
lower compared to non-drinkers. But people who had at least five
drinks daily tripled their stroke risk.
Finally, Danish researchers reported a U-shaped relation between
alcohol intake and risk of stroke, based on the Copenhagen City Heart Study. "In analyses adjusted for age, sex, and smoking," wrote Truelsen, M.D.et al in Epidemiology, "intake of wine on a monthly, weekly, or daily basis was associated
with a lower risk of stroke compared with no wine intake." Furthermore, the relation could be explained as a linear relationship,
indicating a dose-response effect.
Conclusion
These four studies, all published in 1999, contribute to the evidence
demonstrating a protective effect for moderate consumption on
the risk of stroke, particularly for ischemic stroke. Never the
less, contra-dictory results, particularly in the area of hemorrhagic
stroke, continue, as a recent Scottish study published in the
British Medical Journal showed:These researchers found a clear increased risk of stroke
mortality for heavier drinkers (over 22 units–nearly four bottles
of wine–per week), but did not find a protective effect at lower
levels of consumption.
Although some controversy in this area of study will inevitably
remain for some time, it can safely be said that the balance of
studies now point to a favorable asso-ciation between moderate
alcohol consumption and reduced risk of stroke. As the New York
researchers explained in their JAMA article, "While no study has shown benefit in recommending alcohol consumption
to those who do not drink, our data support the view, endorsed
by the NAS in its Stroke Prevention Guidelines, that among those who are moderate drinkers, continued consumption may provide a reduction of ischemic
stroke risk." The continuing threat and devastating effect of stroke – as well
as the unanswered scientific questions–assure us that there will
be many more studies on this important topic as we move into the
next century.
This scientific summary is for educational purposes only. For
more information or a list of references, please contact Elisabeth
Holmgren.
