The Effects of Ethanol on Organ Systems
Although one to two drinks per day in an otherwise healthy and nonpregnant individual can have some beneficial effects, at higher doses alcohol is toxic to most organ systems. Knowledge about the deleterious effects of alcohol helps the physician to identify alcoholic patients and provides information that can be used to help motivate them to abstain. The information offered here generally applies across ages and genders, with common sense differences (e.g., older persons carry higher health risks). It is important to remember that the typical white- or blue-collar alcoholic functions at a fairly high level for years, and that not everyone develops each problem.
Central Nervous System
Approximately 35% of drinkers may experience a blackout, an episode of temporary anterograde amnesia, in which the person forgets all or part of what occurred during a drinking evening. Another common problem, one seen after as few as several drinks, is that alcohol causes alterations between sleep stages and a deficiency in rapid eye movement and deep sleep with resulting prominent and sometimes disturbing dreams later in the night. Finally, alcohol relaxes muscles in the pharynx, which can cause snoring and exacerbate sleep apnea, with symptoms of the latter in 75% of alcoholic men over age 60. As a consequence of alcohol-related impairment in judgment and coordination, at least half of patients with physical trauma have evidence of substance-related impairment, a finding reflecting the fact that 40% of drinkers in the United States have at some time driven while intoxicated.
The effect of alcohol on the nervous system is even more pronounced among alcohol-dependent individuals. Chronic high doses cause peripheral neuropathy in 5 to 15% of alcoholics: patients experience bilateral limb numbness, tingling, and paresthesias, all of which are more pronounced distally. Wernicke’s syndrome (ophthalmoparesis, ataxia, and encephalopathy) and Korsakoff’s syndrome are seen in <10% of alcoholics as the result of thiamine deficiency, especially in persons with transketolase deficiency. Approximately 1% of alcoholics develop cerebellar degeneration, a syndrome of progressive unsteady stance and gait often accompanied by mild nystagmus; neuroimaging studies reveal atrophy of the cerebellar vermis.
Alcoholics can manifest severe cognitive problems including impairment in recent and remote memory for weeks to months after an alcoholic binge. Increased size of the brain ventricles and cerebral sulci are seen in 50% of chronic alcoholics, but these changes are often reversible, returning toward normal within a year or so of abstinence. There is no single alcoholic dementia syndrome; rather, this label is used to describe patients who have apparently irreversible cognitive changes (possibly from diverse causes) and chronic alcoholism.
Finally, almost every psychiatric syndrome can be seen temporarily during heavy drinking or subsequent withdrawal. These include intense sadness lasting for days to weeks in the midst of heavy drinking in 40% of alcoholics, which is classified as an alcohol-induced mood disorder; temporary severe anxiety in 10 to 30% of alcoholics, often beginning during alcohol withdrawal, which can persist for many months after cessation of drinking (alcohol-induced anxiety disorder); and auditory hallucinations and/or paranoid delusions in a clear sensorium (alcohol-induced psychotic disorder) seen temporarily in 1 to 10% of alcoholics. Treatment of all forms of alcohol-induced psychopathology includes abstinence and supportive care, with the likelihood of full recovery within several days to 4 weeks. A history of alcohol intake is an important consideration in any patient with one of these psychiatric symptoms.
The Gastrointestinal System
Esophagus and Stomach
Acute alcohol intake can result in inflammation of the esophagus and stomach, causing epigastric distress and gastrointestinal bleeding. Chronic heavy drinking, if associated with violent vomiting, can produce a Mallory-Weiss lesion, a longitudinal tear in the mucosa at the gastroesophageal junction.
Pancreas and Liver
The incidence of acute pancreatitis (25 per 1000 per year) is almost threefold higher than in the general population, accounting for an estimated 10% or more of the cases of this disorder. Alcohol impairs gluconeogenesis in the liver with a resulting fall in the amount of glucose produced from glycogen; lactate production increases; and there is a decreased oxidation of fatty acids with an increase in fat accumulation in liver cells. In the healthy individual these changes are reversible, but with repeated exposure to ethanol, more severe changes can occur, including fatty accumulation, alcohol-induced hepatitis, perivenular sclerosis, and cirrhosis, with the latter observed in an estimated 15 to 20% of alcoholics.
Drinking as few as 1.5 drinks per day increases a woman’s risk of breast cancer 1.4-fold. For both genders, four drinks per day increases the risk for oral and esophageal cancers approximately threefold and rectal cancers by a factor of 1.5; seven to eight or more drinks per day enhances the risks for many cancers by a factor of five.
Ethanol causes an increase in red blood cell size [mean corpuscular volume, (MCV)], which reflects the effects on stem cells. If heavy drinking is accompanied by folic acid deficiency, there can also be hypersegmented neutrophils, reticulocytopenia, and a hyperplastic bone marrow; if malnutrition is present, sideroblastic changes can be observed. Chronic heavy drinking can decrease production of most white blood cells, decrease granulocyte mobility and adherence, and impair the delayed-hypersensitivity response to new antigens (with a possible false-negative tuberculin skin test). Finally, many alcoholics have mild thrombocytopenia, which usually resolves within a week of abstinence unless there is hepatic cirrhosis or congestive splenomegaly.
Acutely, ethanol decreases myocardial contractility and causes peripheral vasodilation, with a resulting mild decrease in blood pressure and a compensatory increase in cardiac output. Exercise-induced increases in cardiac oxygen consumption are higher after alcohol intake. These acute effects have little clinical significance for the average healthy drinker but can be problematic in men and women with cardiac disease.
The consumption of three or more drinks per day results in a dose-dependent increase in blood pressure, which returns to normal within weeks of abstinence. Heavy drinking is an important contributor to mild to moderate hypertension. Chronic heavy drinking can cause cardiomyopathy, with symptoms ranging from unexplained arrhythmias in the presence of left ventricular impairment to heart failure with dilation of all four heart chambers and hypocontractility of heart muscle. Perhaps one-third of cases of cardiomyopathy are alcohol-induced. Mural thrombi can form in the left atrium or ventricle, while heart enlargement >25% can cause mitral regurgitation. Atrial or ventricular arrhythmias, especially paroxysmal tachycardia, can also occur after a drinking binge in individuals showing no other evidence of heart disease - a syndrome known as the “holiday heart.”
Chronic intake of modest doses of alcohol can have some beneficial effects. A maximum of one to two drinks per day may decrease the risk for cardiovascular death, perhaps through an increase in high-density lipoprotein (HDL) cholesterol or changes in clotting mechanisms. In one large national study, cardiovascular mortality was reduced by 30 to 40% among individuals reporting one or more drinks daily compared to nondrinkers, with overall mortality lowest among those consuming approximately one drink per day. Recent data have also corroborated the decreased risk for ischemic, but not hemorrhagic, stroke associated with regular light drinking.
Genitourinary System Changes, Sexual Functioning, and Fetal Development
Acutely, modest ethanol doses (e.g., blood alcohol concentrations of 100 mg/dL) can both increase sexual drive and decrease erectile capacity in men. Even in the absence of liver impairment, a significant minority of chronic alcoholic men may show irreversible testicular atrophy with concomitant shrinkage of the seminiferous tubules, decreases in ejaculate volume, and a lower sperm count.
The repeated ingestion of high doses of ethanol by women can result in amenorrhea, a decrease in ovarian size, absence of corpora lutea with associated infertility, and spontaneous abortions. Heavy drinking during pregnancy results in the rapid placental transfer of both ethanol and acetaldehyde, which may have serious consequences for fetal development. The fetal alcohol syndrome can include any of the following: facial changes with epicanthal eye folds, poorly formed concha, and small teeth with faulty enamel; cardiac atrial or Ventricular septal defects; an aberrant palmar crease and limitation in joint movement; and microcephaly with mental retardation. The amount of ethanol and/or time of vulnerability during pregnancy have not been defined, making it advisable for pregnant women to abstain completely.
Other Effects of Ethanol
Between one-half and two-thirds of alcoholics have skeletal muscle weakness caused by acute alcoholic myopathy, a condition that improves but which might not disappear with abstinence. Effects of repeated heavy drinking on the skeletal system include alterations in calcium metabolism, lower bone density, and less growth in the epiphyses, with an increased risk for fractures and osteonecrosis of the femoral head. Hormonal changes include an increase in cortisol levels, which can remain elevated during heavy drinking; inhibition of vasopressin secretion at rising blood alcohol concentrations and the opposite effect at falling blood alcohol concentrations (with the final result that most alcoholics are likely to be slightly overhydrated); a modest and reversible decrease in serum thyroxine (T4); and a more marked decrease in serum triiodothyronine (T3).
Alcohol and Alcoholism
- Alcohol and Alcoholism: Introduction
- Alcoholism (Alcohol Abuse or Dependence)
- Identification of the Alcoholic and Intervention
- Rehabilitation of Alcoholics
- The Alcohol Withdrawal Syndrome
Revision date: July 8, 2011
Last revised: by Janet A. Staessen, MD, PhD