Newswise
— A new study led by researchers at Beth Israel Deaconess
Medical Center (BIDMC) and the Harvard School of Public Health
(HSPH) has found that heavy drinkers -- men who consume an
average of three or more alcoholic beverages per day -- are
nearly 45 percent more likely to suffer an ischemic stroke
compared with nondrinkers.
The study also found that while light and moderate drinkers
appear to be at neither greater risk nor greater advantage
than abstainers when it comes to ischemic stroke, the frequency
with which they consume alcohol may modestly influence their
risk.
The findings, reported in the January 4, 2005 issue of the
Annals of Internal Medicine, help shed light on a subject
that has been the source of some confusion, and reinforce
the importance of what the authors call “drinking patterns,”
the number of days per week that alcohol is consumed and the
amount consumed on drinking days.
“In this study, the participants who were at lowest risk for
stroke were the men who consumed one or two drinks on three
to four days of the week,” says lead author Kenneth Mukamal,
MD, MPH, a general internist at BIDMC and Assistant Professor
of Medicine at Harvard Medical School. “The importance of
drinking pattern for stroke risk parallels our previous findings
among this same group of men regarding alcohol consumption
and the risk of developing diabetes and coronary heart disease.
Among all three types of disease, the lowest risk seems to
occur when consumption is limited to one or, at most, two
drinks, approximately every other day, with little benefit
shown above three to four drinking days per week.”
Nearly 700,000 individuals in the U.S. suffer an ischemic
stroke each year. Sometimes referred to as a “brain attack,”
the condition develops when an artery in the brain becomes
blocked by a blood clot. There are two types of ischemic stroke:
thrombotic, which results from the development of a blood
clot within the brain itself, and embolic, which is the result
of a clot traveling through the bloodstream from another part
of the body and becoming lodged in the brain. In both instances,
the ensuing deprivation of oxygen and nutrients to the brain
can result in neurological damage or death.
During the course of the 14-year study the authors followed
38,156 participants who are part of the HSPH-based Health
Professionals Follow-up Study. Beginning in 1986 and continuing
every four years thereafter until 2000, the male participants,
who ranged in age from 40 to 75, responded to a detailed questionnaire
regarding diet and medical history, including alcohol consumption.
The researchers examined the following factors to gauge the
influence of alcohol consumption on the risk for ischemic
stroke: average amount of alcohol consumed; drinking patterns
(number of days per week alcohol was consumed); and type of
beverage consumed (beer, red wine, white wine, or spirits).
They also looked at the incidence of both subtypes of ischemic
stroke – thrombotic and embolic. During the course of the
study, they confirmed 412 cases of ischemic stroke among the
study participants.
Their findings showed that men whose average alcohol intake
was three or more drinks per day had a 42 percent higher risk
of ischemic stroke (particularly embolic stroke) than did
abstainers. This finding, says Mukamal, may be attributable
to alcohol’s association with both high blood pressure and
atrial fibrillation.
Although the findings also found that average intake of lower
amounts of alcohol was associated with neither a significantly
higher nor lower risk of stroke, when drinking frequency was
taken into account, the light and moderate drinkers who consumed
alcohol three to four days per week had a modest 32 percent
lower stroke risk than did nondrinkers.
“I think there has been a subtle assumption that moderate
drinking is associated with a lower risk of ischemic stroke,
similar to the way that it is associated with a lower risk
of heart attack,” says Mukamal. “But our study did not demonstrate
a statistically significant role for alcohol in guarding against
stroke. While there does appear to be a small window for which
light drinking is associated with lower risk, it’s important
to note that this window is smaller than it is for heart disease
and therefore you cannot simply extrapolate between the two.”
Mukamal notes that red wine appeared to offer slightly more
protection than other types of alcohol, with red-wine drinkers
shown to be at 23 percent lower risk of ischemic stroke. (Intake
of one or more glasses per day was linked to a 46 percent
lower risk, but few men in this study drank red wine on a
daily basis, he adds.)
“Compared with other types of alcohol, red wine was associated
with a step-wise lower risk of ischemic stroke,” according
to Mukamal. “This is curious, because among this population
of men, red wine is not linked to a lower risk of heart disease
any more than any other type of alcohol, so it’s unclear why
this would be the case with stroke.” He adds that further
research will be needed to help clarify this finding.
For now, the standard recommendation that men drink no more
than two drinks per drinking day still appears to be a good
one, say the authors.
“Our findings directly support current public health recommendations
stating that men should consume less than two drinks per day,”
the authors write. “At the same time, our findings support
the safety of continued light alcohol consumption among adults
who have been able to appropriately regulate the quality and
timing of their alcohol use.”
Study coauthors include senior author Eric Rimm, ScD, Walter
Willett, MD, DrPH, Alberto Ascherio, MD, DrPH, Ichiro Kawachi,
MD, PhD, and Meir Stampfer, MD, DrPH, of the Harvard School
of Public Health; Murray Mittleman, MD, DrPH, of Beth Israel
Deaconess Medical Center; Katherine Conigrave, MD, of Royal
Prince Albert Hospital, Camperdown, Australia; and Carlos
Camargo Jr., MD, DrPH, of Massachusetts General Hospital.
This study was supported by grants from the National Institutes
of Health.
Beth Israel Deaconess Medical Center is a patient care, teaching
and research affiliate of Harvard Medical School, and ranks
third in National Institutes of Health funding among independent
hospitals nationwide. BIDMC is clinically affiliated with
the Joslin Diabetes Center and is a research partner of Dana-Farber/Harvard
Cancer Center. BIDMC is the official hospital of the Boston
Red Sox. For more information, visit www.bidmc.harvard.edu.
Harvard School of Public Health is dedicated to advancing
the public’s health through learning, discovery, and communication.
More than 300 faculty members are engaged in teaching and
training the 800-plus student body in a broad spectrum of
disciplines crucial to the health and well-being of individuals
and populations around the world. Programs and projects range
from the molecular biology of AIDS vaccines to the epidemiology
of cancer; from risk analysis to violence prevention; from
maternal and children’s health to quality of care measurement;
from health care management to international health and human
rights. http://www.hsph.harvard.edu.
