Alcohol-induced impairment of central nervous system function: behavioral skills involved in driving

Several points emerge from the large body of data on the effects of alcohol on CNS function. First, the degree of impairment is dose related, but not identical or strictly linear for all behaviors. Alcohol-related impairment of behavioral skills involved in driving is greatest for those tasks that require cognitive functioning; simple perception alone is least affected. Impairment of cognitive functioning, which includes information processing and decision making under conditions of divided attention, is evident at BALs above 50 mg/dl and is markedly affected above 100 mg/dl. Above a BAL of 100 mg/dl, almost all behavioral skills are impaired by alcohol. Most studies have employed only one or at most two doses of alcohol in testing for impairment. The limited range of BALs studied makes determination of the overall shape of the dose-response curve difficult. Second, alcohol-related impairment of CNS functions cannot be demonstrated at low BALs. There is no consistent evidence that BALs below 50 mg/dl impair any behavior in most individuals. Youth and the elderly, groups not typically studied in the laboratory, may represent exceptions to this general observation. Nonetheless, these findings are more consistent with a threshold effect for impairment than for impairment at all levels of BAL. Third, for most behavioral skills, the decrement in performance after alcohol is slight, rarely exceeding 35-50% of the control period. In many studies, changes of only 8-10% are reported to be statistically significant. Whether these small statistically significant decrements in performance are an explanation for increased crash risk remains uncertain.(ABSTRACT TRUNCATED AT 250 WORDS)