The influence of blood alcohol concentrations of around 0.03% on neuropsychological functions - a double-blind, placebo-controlled investigation

There is a general agreement that blood alcohol concentrations (BACs) of about 0.05% result in impairment of the ability to drive. This fact has been supported by means of experiments. In addition, there are only a few studies to date investigating low BACs. The present study aims to investigate the extent and quality of cognitive changes in low BACs of around 0.03%. Sixteen healthy male subjects were examined in a double-blind, placebo-controlled study. During the trials the BAC was regulated to about 0.03%. As part of the study a record was made of the general level of intelligence, subjective impairments, possible depressive symptoms, general ability to perform, vigilance, divided attention, response times and performance of memory. Statistical analysis took place using the two-period crossover design. Verbal intelligence, general performance, vigilance (optical stimuli), divided attention, vigilance towards acoustic stimuli and the general response time to acoustic and visual-acoustic sequential stimuli, and memory were not impaired significantly by a BAC of around 0.03%. The total response and motor response time to optical stimuli as well as decision time about sequential optical stimuli were, however, significantly changed for BACs of around 0.03%. In conclusion, the present results show that already in BACs of around 0.03%, particular cognitive functions which rely on perception and processing of visual information, are significantly impaired. This was evident in the more complex and urgent tasks.