Influence of alcohol on sleep, cortisol secretion and memory consolidation. Results of a randomised controlled trial

Background. Sleep enhances memory consolidation. Chronic consumption of 0.4 g alcohol/kg bodyweight has a negative impact on cognitive function. An artificial increase of cortisol during the first half of the night impairs declarative memory consolidation. Alcohol can stimulate cortisol secretion. Objectives. Does the acute consumption of this amount of alcohol have a negative impact on sleep, memory, and secretion of cortisol? Material and methods. In a double-blind randomized cross-over design, 34 healthy young males received 0.4 g alcohol/kg bodyweight or an isotonic transfusion of sodium chloride during early NonREM sleep. Before sleep, they had learned a declarative and a procedural memory task that had to be recalled the next morning when alcohol had levelled off. Results and Conclusions. Alcohol increased cortisol secretion in the early night and resulted in an attenuated cortisol awakening response. In addition, latencies for REM and sleep stage 4 and the time spent in sleep stage 1 and wake states were increased. Subjects felt less refreshed in the morning after alcohol transfusion, but memory recall was unchanged. Alcohol at a moderate dose thus had a negative impact on cortisol rhythm and some sleep parameters, but this effect was not strong enough to influence overnight memory consolidation.