Chronic and high alcohol consumption has a negative impact on sleep and sleep-associated consolidation of declarative memory.

ABSTRACT

BACKGROUND: The importance of sleep for memory consolidation has become a major focus of research. While it is known that abstaining alcohol-dependent patients often have sleep disorders and that there is some cognitive impairment during early abstention a possible interaction of disturbed sleep with overnight memory consolidation has not been addressed in a study as yet. METHODS: Twenty-four alcohol-dependent patients with a short abstention period (mean 21.9 +/- 7.6 days) were compared with 12 patients with an abstention period of several months (115.7 +/- 43.8 days). Groups did not differ with respect to daily alcohol consumption before treatment, duration of alcohol dependence, and age. Before sleep all patients learned a list of semantically associated word pairs and a face name association task to a fixed criterion (at least 60% of correct recall) and they performed a mirror tracing task. After a polysomnographically registered night the patients were tested for retention of the learned declarative material by cued recall and had to perform the mirror tracing task again. RESULTS: The groups did not differ with respect to sleep parameters or sleep-associated memory consolidation. Across both groups the duration of alcohol dependence correlated negatively with the amount of non-REM sleep and recall in the face name association task correlated negatively with daily alcohol consumption before abstention. Among the longer-term abstainers the duration of abstention correlated with the amount of slow wave sleep. CONCLUSIONS: Our data support the hypothesis that chronic and high alcohol consumption negatively affects sleep and declarative memory consolidation during the first months of abstention. Between an abstention period of a few weeks and of several months no change in sleep parameters and nightly memory consolidation could be demonstrated, however.