Contribution of Alcohol to Medical Diseases
Alcohol contributes to many major medical diseases, including liver damage, heart disease, and neurological disorders. Alcohol abuse and alcoholism account for 4.5% of worldwide disability-adjusted life years (DALYs), the number of years one loses from a working life expectancy, and these values increase to 6.7% in high-income countries (box 6.6).
Chronic, high-dose alcohol can lead to fatty liver, alcoholic hepatitis, and ultimately cirrhosis of the liver. In such a diseased condition, alcohol is used preferentially for fuel in the liver, displacing up to 90% of the liver’s normal metabolic substrates. Acetaldehyde accumulates, alcohol-oxidizing activity increases, and alcohol dehydrogenase-mediated nicotinamide adenine dinucleotide reductase (NADH) accumulates. All of these metabolic effects can lead to hepatotoxicity. Alcoholic cirrhosis usually develops after more than a decade of heavy drinking. The amount of alcohol that can injure the liver varies greatly from person to person. In women, as few as two to three drinks per day have been linked with cirrhosis. In men, as few as three to four drinks per day are needed. The US National Institute on Alcohol Abuse and Alcoholism reported that liver cirrhosis was the 12th leading cause of death in 2009 (a total of 31,522 deaths). Of these cirrhosis deaths, 48% were directly attributable to alcohol.
DISABILITY-ADJUSTED LIFE YEARS (DALYs)The World Health Organization (WHO) provides a comprehensive framework for studying health risks that was developed for The World Health Report 2002, which presented estimates for the year 2000. An update for the year 2004 for 24 global risk factors has been provided. It uses updated information from WHO programs and scientific studies for both exposure data and the causal associations between risk exposure and disease and injury outcomes. The burden of disease attributable to risk factors is measured in terms of lost years of healthy life using the metric “disability-adjusted life year” (DALY). The DALY combines years of life lost due to premature death and years of healthy life lost due to illness and disability. Although there are many possible definitions of “health risk,” it is defined in the report as “a factor that raises the probability of adverse health outcomes.” The report focuses on selected risk factors that have global spread, for which data are available to estimate population exposures or distributions, and for which the means to reduce them are known. Five leading risk factors were identified in this report: childhood underweight, unsafe sex, alcohol use, unsafe water and sanitation, and high blood pressure. These were responsible for 25% of all deaths in the world and 20% of all DALYs. Reducing exposure to these risk factors would increase global life expectancy by nearly 5 years. World Health Organization. Global Health Risks: Mortality and Burden of Disease Attributable to Selected Major Risks. World Health Organization, Geneva, 2009.
Heavy drinking is also associated with increased mortality from heart disease. Alcohol can cause cardiomyopathy, which is decreased function of the heart muscle. Moderate drinking, in contrast, has been associated with beneficial effects on the cardiovascular system caused by increases in high-density lipoproteins (that is, “good cholesterol”). Heavy alcohol intake is also associated with cancers of the mouth, tongue, esophagus, liver, pancreas, pharynx, larynx, stomach, lung, colon, and rectum.
Alcohol and cancer vulnerability involve a powerful interaction with smoking, which is historically high among individuals with alcoholism. Over decades, the association between alcohol drinking and smoking has been high, as has the negative association between alcohol consumption and the likelihood to quit smoking. In 2000, the National Institute on Alcohol Abuse and Alcoholism reanalyzed data from its 1992 National Longitudinal Alcohol Epidemiology Survey. The total sample size was 42,862. The prevalence of smoking was 28% among lifetime abstainers from alcohol, 49% among light drinkers, and 73% among heavy drinkers. According to this same survey, of the people with a lifetime history of alcohol abuse or dependence, 68% smoked, compared with 46% of people without these disorders.