The 10th ICAP report discusses how even low levels of alcohol
may be problematic for some individuals and populations. The paper
argues that greater attention needs to be given to the drinking
patterns of these "special populations" as to how much or even
whether they drink.
Biological vulnerability to alcohol is distinguished from those
at risk because of their heavy and chronic alcohol consumption.
The risk factors are different, as are the implications for prevention,
although there are areas of overlap. Research suggests that those
with the highest genetic risk become heavy drinkers quite early
in life, continuing as heavy drinkers as adults.
Biological Vulnerability to alcohol The genetic makeup of an individual,
general health status, or the presence of a particular medical
condition may confer vulnerability to alcohol. Variables such
as gender, race, and age also play a role, all influencing the
way in which ethanol is metabolized by the human body and the
way in which it interacts with other biological functions.
Genetics Research such as the ongoing Collaborative Study on the
Genetics of Alcoholism (COGA), in the US, suggest that variations
in several genes may be involved, including those coding for the
enzymes responsible for metabolizing alcohol and those coding
for receptors to neuro-transmitters responsible for how the brain
responds to alcohol.
For some populations, genetic vulnerability means low tolerance
to alcohol and the inability to process it, while for others it
is an increased risk for alcohol abuse or dependence. The genetic
variations could possibly be used to identify vulnerable individuals.
Genetic makeup with an increased risk for alcohol abuse and dependence
seems to have a familial component to vulnerability. Data from
the US and Western Europe suggest that an estimated 5 to 10 %
of female relatives of alcoholics and 25% of male relatives will
themselves develop alcohol dependence.
An example of genetic variation is shown among Asians. Here, alcohol
metabolism is impaired by a nonfunctional form of the enzyme aldehyde
dehydrogenase (ALDH). Adverse reactions to even small amounts
of alcohol include facial flushing, nausea, heart palpitations,
and dizziness Research suggests 25-40% of Japanese, 25% of Han
Chinese and 15-30% of Koreans are affected.
Health Status As well as genetic pre-disposition,an important
determinant of susceptibility to potential adverse effects of
alcohol is health status. This includes general health, nutritional
state, and certain ailments and conditions.
As regards nutrition the malnourished are especially vulnerable.Thiamine
deficiency, most often seen in chronic alcohol abusers, has been
linked with neurological impairment and Wernicke-Korsakoff syndrome.
As regards illness, individuals with hypertension may be adversely
affected by drinking and for those infected with hepatitis C,
alcohol may accelerate the rate of liver damage and increase the
risk of cirrhosis.
Gender A smaller blood volume and higher proportion of body fat
mean that the effects of alcohol are felt at lower doses in women
than they are in men. They also metabolize alcohol differently.
The activity of ADH, the other key enzyme involved in the breakdown
of ethanol, is roughly 70-80% greater in men than it is in women.
This difference diminishes in post-menopausal women, whose estrogen
levels do not fluctuate with the menstrual cycle.
Age It has been shown that the activity of ADH decreases with
age, especially in men, increasing susceptibility to the effects
of ethanol. The elderly are more likely to suffer poor health,take
medications plus changes in general metabolism with age may also
put them at increased risk.
Much of the research on the effects of alcohol on these processes
is derived from animal models and from experiments conducted in
vitro. Consequently, some caution is required when extrapolating
these data to humans, as the levels of alcohol needed to effect
changes in animal models are often significantly different from
the conditions created when people drink.
Policy implications The paper concludes that measurable markers
that identify at-risk individuals may bring about new approaches
to both screening and education measures. Physicians should be
educated in advances in this area and the biology of vulnerability
to alcohol understood in order to provide their patients with
accurate and balanced advice that addresses each ones particular
needs. Finally the importance of encouraging research aimed both
at identifying the sources of vulnerability is stressed plus new
strategies for using such findings for the purposes of prevention.