ALCOHOL’S DAMAGING EFFECTS ON THE BRAIN
Difficulty walking, blurred vision, slurred speech,
slowed reaction times, impaired memory: Clearly,
alcohol affects the brain. Some of these
impairments are detectable after only one or two
drinks and quickly resolve when drinking stops.
On the other hand, a person who drinks heavily
over a long period of time may have brain deficits
that persist well after he or she achieves sobriety.
Exactly how alcohol affects the brain and the
likelihood of reversing the impact of heavy
drinking on the brain remain hot topics in alcohol
research today.
We do know that heavy drinking may have
extensive and far–reaching effects on the brain,
ranging from simple “slips” in memory to
permanent and debilitating conditions that require
lifetime custodial care. And even moderate
drinking leads to short–term impairment, as
shown by extensive research on the impact of
drinking on driving.
A number of factors influence how and to what
extent alcohol affects the brain (1), including
how much and how often a person drinks;
the age at which he or she first began drinking,
and how long he or she has been drinking;
the person’s age, level of education, gender,
genetic background, and family history of
alcoholism;
whether he or she is at risk as a result of
prenatal alcohol exposure; and
his or her general health status.
This Alcohol Alert reviews some common
disorders associated with alcohol–related brain
damage and the people at greatest risk for
impairment. It looks at traditional as well as
emerging therapies for the treatment and
prevention of alcohol–related disorders and
includes a brief look at the high–tech tools that
are helping scientists to better understand the
effects of alcohol on the brain.
BLACKOUTS AND MEMORY LAPSES
Alcohol can produce detectable impairments in
memory after only a few drinks and, as the
amount of alcohol increases, so does the degree
of impairment. Large quantities of alcohol,
especially when consumed quickly and on an
empty stomach, can produce a blackout, or an
interval of time for which the intoxicated person
cannot recall key details of events, or even entire
events.
Blackouts are much more common among social
drinkers than previously assumed and should be
viewed as a potential consequence of acute
intoxication regardless of age or whether the
drinker is clinically dependent on alcohol (2).
White and colleagues (3) surveyed 772 college
undergraduates about their experiences with
blackouts and asked, “Have you ever awoken
after a night of drinking not able to remember
things that you did or places that you went?” Of
the students who had ever consumed alcohol, 51
percent reported blacking out at some point in
their lives, and 40 percent reported experiencing a
blackout in the year before the survey. Of those
who reported drinking in the 2 weeks before the
survey, 9.4 percent said they blacked out during
that time. The students reported learning later
that they had participated in a wide range of
potentially dangerous events they could not
remember, including vandalism, unprotected sex,
and driving.
Equal numbers of men and women reported
experiencing blackouts, despite the fact that the
men drank significantly more often and more
heavily than the women. This outcome suggests
that regardless of the amount of alcohol
consumption, females—a group infrequently
studied in the literature on blackouts—are at
greater risk than males for experiencing
blackouts. A woman’s tendency to black out
more easily probably results from differences in
how men and women metabolize alcohol. Females
also may be more susceptible than males to
milder forms of alcohol–induced memory
impairments, even when men and women
consume comparable amounts of alcohol (4).
ARE WOMEN MORE VULNERABLE TO
ALCOHOL’S EFFECTS ON THE BRAIN?
Women are more vulnerable than men to many of
the medical consequences of alcohol use. For
example, alcoholic women develop cirrhosis (5),
alcohol–induced damage of the heart muscle
(i.e., cardiomyopathy) (6), and nerve damage
(i.e., peripheral neuropathy) (7) after fewer years
of heavy drinking than do alcoholic men. Studies
comparing men and women’s sensitivity to
alcohol–induced brain damage, however, have
not been as conclusive.
Using imaging with computerized tomography,
two studies (8,9) compared brain shrinkage, a
common indicator of brain damage, in alcoholic
men and women and reported that male and
female alcoholics both showed significantly
greater brain shrinkage than control subjects.
Studies also showed that both men and women
have similar learning and memory problems as a
result of heavy drinking (10). The difference is
that alcoholic women reported that they had been
drinking excessively for only about half as long as
the alcoholic men in these studies. This indicates
that women’s brains, like their other organs, are
more vulnerable to alcohol–induced damage than
men’s (11).
Yet other studies have not shown such definitive
findings. In fact, two reports appearing side by
side in the American Journal of Psychiatry
contradicted each other on the question of
gender–related vulnerability to brain shrinkage in
alcoholism (12,13). Clearly, more research is
needed on this topic, especially because alcoholic
women have received less research attention than
alcoholic men despite good evidence that women
may be particularly vulnerable to alcohol’s effects
on many key organ systems.
BRAIN DAMAGE FROM OTHER CAUSES
People who have been drinking large amounts of
alcohol for long periods of time run the risk of
developing serious and persistent changes in the
brain. Damage may be a result of the direct
effects of alcohol on the brain or may result
indirectly, from a poor general health status or
from severe liver disease.
For example, thiamine deficiency is a common
occurrence in people with alcoholism and results
from poor overall nutrition. Thiamine, also known
as vitamin B1, is an essential nutrient required by
all tissues, including the brain. Thiamine is found
in foods such as meat and poultry; whole grain
cereals; nuts; and dried beans, peas, and
soybeans. Many foods in the United States
commonly are fortified with thiamine, including
breads and cereals. As a result, most people
consume sufficient amounts of thiamine in their
diets. The typical intake for most Americans is 2
mg/day; the Recommended Daily Allowance is 1.2
mg/day for men and 1.1 mg/day for women (14).
Wernicke–Korsakoff Syndrome
Up to 80 percent of alcoholics, however, have a
deficiency in thiamine (15), and some of these
people will go on to develop serious brain
disorders such as Wernicke–Korsakoff syndrome
(WKS) (16). WKS is a disease that consists of
two separate syndromes, a short–lived and
severe condition called Wernicke’s
encephalopathy and a long–lasting and
debilitating condition known as Korsakoff’s
psychosis.
The symptoms of Wernicke’s encephalopathy
include mental confusion, paralysis of the nerves
that move the eyes (i.e., oculomotor
disturbances), and difficulty with muscle
coordination. For example, patients with
Wernicke’s encephalopathy may be too confused
to find their way out of a room or may not even
be able to walk. Many Wernicke’s encephalopathy
patients, however, do not exhibit all three of these
signs and symptoms, and clinicians working with
alcoholics must be aware that this disorder may
be present even if the patient shows only one or
two of them. In fact, studies performed after
death indicate that many cases of thiamine
deficiency–related encephalopathy may not be
diagnosed in life because not all the “classic”
signs and symptoms were present or recognized.
Approximately 80 to 90 percent of alcoholics with
Wernicke’s encephalopathy also develop
Korsakoff’s psychosis, a chronic and debilitating
syndrome characterized by persistent learning and
memory problems. Patients with Korsakoff’s
psychosis are forgetful and quickly frustrated and
have difficulty with walking and coordination (17).
Although these patients have problems
remembering old information (i.e., retrograde
amnesia), it is their difficulty in “laying down” new
information (i.e., anterograde amnesia) that is the
most striking. For example, these patients can
discuss in detail an event in their lives, but an
hour later might not remember ever having the
conversation.
Treatment
The cerebellum, an area of the brain responsible
for coordinating movement and perhaps even
some forms of learning, appears to be particularly
sensitive to the effects of thiamine deficiency and
is the region most frequently damaged in
association with chronic alcohol consumption.
Administering thiamine helps to improve brain
function, especially in patients in the early stages
of WKS. When damage to the brain is more
severe, the course of care shifts from treatment to
providing support to the patient and his or her
family (18). Custodial care may be necessary for
the 25 percent of patients who have permanent
brain damage and significant loss of cognitive
skills (19).
Scientists believe that a genetic variation could be
one explanation for why only some alcoholics with
thiamine deficiency go on to develop severe
conditions such as WKS, but additional studies
are necessary to clarify how genetic variants
might cause some people to be more vulnerable
to WKS than others.
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