Sleep, sleep homeostasis and arousal disturbances in alcoholism

The effects of alcohol on human sleep were first described almost 70 years ago. Since then, accumulating evidences suggest that alcohol intake at bed time immediately induces sleep [reduces the time to fall asleep (sleep onset latency), and consolidates and enhances the quality (delta power) and the quantity of sleep]. Such potent sleep promoting activity makes alcohol as one of the most commonly used "over the counter" sleep aid. However, the somnogenic effects, after alcohol intake, slowly wane off and often followed by sleep disruptions during the rest of the night. Repeated use of alcohol leads to the development of rapid tolerance resulting into an alcohol abuse. Moreover, chronic and excessive alcohol intake leads to the development of alcohol use disorder (AUD). Alcoholics, both during drinking periods and during abstinences, suffer from a multitude of sleep disruptions manifested by profound insomnia, excessive daytime sleepiness, and altered sleep architecture. Furthermore, subjective and objective indicators of sleep disturbances are predictors of relapse. Finally, within the USA, it is estimated that societal costs of alcohol-related sleep disorders exceed $18 billion. Thus, although alcohol associated sleep problems have significant economic and clinical consequences, very little is known about how and where alcohol acts to affect sleep. In this review, a conceptual framework and clinical research focused on understanding the relationship between alcohol and sleep is first described. In the next section, our new and exciting preclinical studies, to understand the cellular and molecular mechanism of how acute and chronic alcohol affects sleep, are described. In the end, based on observations from our recent findings and related literature, opportunities for the development of innovative strategies to prevent and treat AUD are proposed.