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.