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.