Cognitive Impairment & Recovery
Brain damage is a common & potentially severe consequence of long-term,
heavy alcohol consumption. Even mild-to-moderate drinking can adversely
affect cognitive functioning (i.e., mental activities that involve
acquiring, storing, retrieving & using information) 1.
Persistent cognitive impairment can contribute to poor job performance in
adult alcoholics & can interfere with learning & academic achievement in
adolescents with an established pattern of chronic heavy drinking 2.
A small but significant proportion of the heaviest drinkers may develop
devastating, irreversible brain-damage syndromes, such as
Wernicke-Korsakoff syndrome, a disorder in which the patient is incapable
of remembering new information for more than a few seconds 3.
It stands to reason that cognitive impairment also may impede recovery
from alcoholism, although evidence has not conclusively shown this to be
the case. For example, Morgenstern & Bates 4 studied whether deficits in
a patient's learning & planning abilities-core aspects of many treatment
strategies-affected recovery from alcoholism.
They found that impairment was not a significant predictor of poor
treatment response. On the other hand, evidence does support the
possibility that brain damage, whether resulting from or predating
alcohol use, may contribute to the development & progression of
alcoholism 5.
Designing practical strategies to cope with the complex combination of
alcoholism & cognitive impairment requires an understanding of the nature
of cognitive functions & their interactions with structural & functional
brain abnormalities.
This issue of Alcohol Alert describes the nature & consequences of common
alcohol-associated cognitive defects, explores the extent to which some
cognitive abilities recover with abstinence & summarizes recent research
on the effects of cognitive deficits on alcoholism treatment outcome.
Cognition & Alcohol
Most alcoholics exhibit mild-to-moderate deficiencies in intellectual
functioning 6, along with diminished brain size & regional changes in
brain-cell activity. The most prevalent alcohol-associated brain
impairments affect visuospatial abilities & higher cognitive functioning
7. Visuospatial abilities include perceiving & remembering the relative
locations of objects in 2- & 3-dimensional space. Examples include
driving a car or assembling a piece of furniture based on instructions
contained in a line drawing. Higher cognitive functioning includes the
abstract-thinking capabilities needed to organize a plan, set it in
motion & change it as needed 2.
Most alcoholics entering treatment perform as well as nonalcoholics on
tests of overall intelligence. However, alcoholics perform poorly on
neuropsychological tests that measure specific cognitive abilities 8. For
example, an alcoholic who has remained abstinent after treatment may have
no apparent difficulty filing office documents correctly, a task that
engages multiple brain regions. However, that same person might be unable
to devise a completely different filing system, a task closely associated
with higher cognitive functioning.
How Much Is Too Much?
The link between duration & lifetime quantity of drinking & the
development of cognitive problems is unclear. Some investigators have
proposed that cognitive performance worsens in direct proportion to the
severity & duration of alcoholism 6,9. Studies suggest that social
drinkers who consume more than 21 drinks per week also fit into this
category 6. Other investigators have suggested that cognitive deficits
may be detectable only in those alcoholics who have been drinking
regularly for 10 years or more 8,10. Long-term, light-to-moderate social
drinkers have been found to fall into this category as well, showing
cognitive deficits equivalent to those found in detoxified alcoholics 8.
Although further research is needed to determine how a person's pattern
of drinking is related to cognitive impairment, some deficits are
possible even in people who are not heavy drinkers.
Tracking Structural & Functional Brain Abnormalities
Structural & functional brain abnormalities generally are measured by
noninvasive imaging techniques that provide a picture of the living brain
with minimal risk to the individual. Structural imaging techniques, such
as computed tomography & magnetic resonance imaging, are used to generate
computerized pictures of living tissue. Functional imaging techniques,
such as positron emission tomography & magnetic resonance spectroscopy,
permit scientists to study cell activity by tracking blood flow & energy
metabolism. For more information about imaging, see Alcohol Alert No. 47,
"Imaging & Alcoholism: A Window on the Brain."
Structural imaging consistently reveals that compared with nonalcoholics,
most alcoholics' brains are smaller & less dense 11,12. Loss of brain
volume is most noticeable in two areas: the outer layer (i.e., the
cortex) of the frontal lobe, which is considered a major center of higher
mental functions 7,12,13 & the cerebellum, which is responsible largely
for gait & balance as well as certain aspects of learning 14. Support for
these results is provided by functional imaging studies, which reveal
altered brain activity throughout the cortex & cerebellum of heavy
drinkers 15. In addition, functional imaging often is sufficiently
sensitive to detect these irregularities before they can be observed by
structural imaging techniques & even before major cognitive problems
themselves become manifest. This suggests that functional imaging may be
particularly useful for detecting the early stages of cognitive decline
15.
Understanding the Basis of Cognitive Impairment
Accurate measurement of cognitive abilities is challenging & relating
those abilities to a specific brain irregularity simply may not be
possible with the current technology 16. Discrepancies among research
findings have led scientists to develop improved cognitive-measuring
techniques. Using a battery of tests, Beatty & colleagues 9 have
suggested that widespread (i.e., diffuse) cognitive impairment could
arise from damage to multiple brain areas, each of which regulates
distinct but related abilities. Likewise, damaging the network of brain
cells that synchronizes the overall activity of those multiple areas may
produce the same cognitive impairments previously attributed to localized
damage 9.
Is Impairment Reversible?
Certain alcohol-related cognitive impairment is reversible with
abstinence 17. Newly detoxified adult alcoholics often exhibit mild yet
significant deficits in some cognitive abilities, especially
problem-solving, short-term memory & visuospatial abilities 18. By
remaining abstinent, however, the recovering alcoholic will continue to
recover brain function over a period of several months to 1 year 19-with
improvements in working memory, visuospatial functioning &
attention-accompanied by significant increases in brain volume, compared
with treated alcoholics who have subsequently relapsed to drinking 18.
Rewiring Brain Networks
Reversibility of alcohol-related cognitive function also may be the
result of a reorganization of key brain-cell networks. Some researchers
have proposed that such reorganization may contribute to the success of
alcoholism treatment. Using advanced imaging techniques, Pfefferbaum &
colleagues 20 examined the brain activity of cognitively impaired
alcoholic participants during a series of tests designed to assess
cognitive function. They found that although the alcoholic subjects had
abnormal patterns of brain activation, compared with control subjects,
they were able to complete the tasks equally well, suggesting that the
brain systems in alcoholics can be functionally reorganized so that tasks
formerly performed by alcohol-damaged brain systems are shunted to
alternative brain systems. This finding-that cognitively impaired
alcoholic patients use different brain pathways than unimpaired patients
to achieve equivalent outcome-also was suggested in a study of patients
in 12-step treatment programs 4. Functional brain reorganization may be
particularly advantageous for adolescent alcohol abusers in treatment,
because their developing brains are still in the process of establishing
nerve-cell networks 21.
Cognitive Function & Alcoholism Treatment
The exact role that cognitive function has in alcoholism treatment
success is unclear. Structural & functional imaging, as well as more
specific cognitive tests, may provide scientists with the tools needed to
reveal subtle relationships between alcohol-related cognitive impairment
& recovery. Meanwhile, certain conclusions can be drawn from existing
research that help to explain how cognitive function may influence
alcoholism treatment:
* Cognitive deficits have been hypothesized to affect the efficacy of
alcoholism treatment, although a clear association has not been
established. One view finds that cognitively impaired patients may not
be able to comprehend the information imparted during therapy & thus,
may not make full use of the strategies presented, thereby hampering
recovery. Another view is that cognitive functioning may not directly
influence treatment outcome, but may impact other factors that, in
turn, contribute to treatment success 22. Focusing on those
factors-such as improved nutrition, opportunities for , careful
evaluation of comorbid mental or medical disorders, and/or treatment
strategies aimed at enticing the patient out of long-standing social
isolation-ultimately may be more beneficial than focusing exclusively
on recovery from alcoholism.
* Other types of non-alcohol-related brain damage also can produce
symptoms resembling those associated with chronic alcoholism.
Clinicians must be aware that no matter the cause of the impairment, it
may have an impact on the patient's ability to benefit fully from
alcohol-treatment strategies.
* Cognitive impairment is usually most severe during the first weeks of
abstinence, perhaps making it difficult for some alcoholics to benefit
from educational & skill-development sessions, which are important
components of many treatment programs 22,23. For example, one study
found that alcoholics tested soon after entering treatment were unable
to recall treatment-related information presented in a film they had
just been shown 4. As time goes by & cognitive function improves,
however, patients may make better use of information presented to them
in individual & group therapy, educational programs & 12-step programs.
Cognitive Impairment & Recovery From Alcoholism-
A Commentary by NIAAA Director Enoch Gordis, M.D.
The new noninvasive imaging techniques that allow us to "see" how the
brain operates have been a boon to the study of cognition. Through this
medium, we now know that the brain is capable of "rewiring" itself. In
doing so, the brain can regain some of the cognitive abilities previously
diminished as a result of damage from alcohol or other diseases. The
brain's remarkable ability to recover is important for at least two
reasons. First, alcohol use over a period of time, even at low levels of
drinking, can produce varying degrees of cognitive damage, a problem that
is of particular concern because alcohol use is so widespread. Thus, the
brain's self-repairing ability may help defer or reduce alcohol-induced
cognitive problems among a large portion of the population. Second, the
brain's ability to rewire itself may have implications in terms of
adolescent drinking. Recent evidence suggests that the adolescent brain,
which is still forming important cellular connections, is more vulnerable
than the adult brain to alcohol-induced damage. This is particularly
troubling, given the problems associated with chronic binge drinking,
which is all too common among young people. The brain's ability to rewire
important neurological systems might help mitigate a lifetime of
cognitive difficulties resulting from chronic drinking during
adolescence, but we do not yet know if this is true. Future research will
help clarify this & other important questions about alcohol's effect on
cognition.
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