Alcohol-induced drowsiness and vigilance performance.

Abstract

Visual vigilance was tested in 8 male and 7 female social drinkers (aged 21-26) after they drank, 0, 0.5, 0.8 and 1.2 g of 95% alcohol/kg of body weight. The mean blood alcohol concentrations before the task were 0.0362, 0.070 and 0.102%. The subjects viewed pseudo-randomly presented signal lights embedded in nonresponse stimuli occurring at 1-s intervals in an oscilloscope for 30 min. The percentage of correct key-press responses was significantly lower after the high dose of alcohol and the response time was significantly longer. Deterioration in performance was also related to time at the task but there were no significant interactions with the alcohol effect. Men consistently detected more signals than did the women; the 2-way analysis of variance indicated significant main effects for alcohol and sex but not interaction. Eyelid position was continuously monitored; over all, 66% of the misses occurred with the eyes open, 26% with the eyes closed longer than 1 s, and 8.3% from eyeblinks (less than 1 s). Alcohol had the greatest effect on eyelid-closed misses; the effect increased linearly with the dose, ranging from a mean of 1.7 misses/30 signals after the placebo to 7.2 misses/30 after the high alcohol dose. The percentage of time the eye was closed increased from 2.5 in the placebo to 6.3, 11.9 and 17.1, respectively, after the low, medium and high doses of alcohol.