Alcohol is a highly-abused substance that greatly exacerbates sleep problems. During abstinence, residual disruptions in sleep maintenance and sleep architecture are the greatest predictors of relapse .
Moderate alcohol consumption 30-60 minutes before bedtime catalyzes disruptions in sleep maintenance and sleep architecture that are mediated by blood alcohol levels . Disruptions in sleep maintenance are most marked once alcohol has been completely metabolized from the body. Under conditions of moderate alcohol consumption where blood alcohol levels average 0.06-0.08 percent and decrease 0.01-0.02 percent per hour, an alcohol clearance rate of 4-5 hours would coincide with disruptions in sleep maintenance in the second half of an 8 hr sleep episode . In terms of sleep architecture, moderate doses of alcohol facilitate "rebounds" in rapid eye movement (REM) and stage 1 sleep; following suppression in REM and stage 1 sleep in the first half of an 8 hr sleep episode, REM and stage 1 sleep increase well beyond baseline in the second half. Moderate doses of alcohol also increase slow wave sleep (SWS) in the first half of an 8 hr sleep episode . Enhancements in REM sleep and SWS following moderate alcohol consumption are mediated by reductions in glutamatergic activity by adenosine in the central nervous system . In addition, tolerance to changes in sleep maintenance and sleep architecture develops within 3 days of alcohol consumption before bedtime .
Low doses of alcohol (one 12 oz. beer) are sleep-promoting by increasing total sleep time and reducing awakenings during the night. The sleep-promoting benefits of alcohol dissipate at moderate and higher doses of alcohol (two 12 oz beers and three 12 oz. beers, respectively) . Previous experience with alcohol also determines whether or not alcohol is a "sleep promoter" or "sleep disrupter." Under free-choice conditions, in which subjects chose between drinking alcohol or water, inexperienced drinkers were sedated while experienced drinkers were stimulated following alcohol consumption . In insomniacs, moderate doses of alcohol improve sleep maintenance .
Sleepiness influences the severity of alcohol consumption. Conditions of sleep deprivation encourage more episodes of alcohol consumption . Increased alcohol consumption during the winter months for Northern climate residents is attributed to escalations in fatigue .
Sleep and hormonal disruptions following withdrawal from chronic alcohol consumption are the greatest predictors of relapse . During abstinence, recovering alcoholics have attenuated melatonin secretion in the beginning of a sleep episode, resulting in prolonged sleep latencies . Escalations in cortisol and core body temperatures during the sleep period contribute to poor sleep maintenance [7,8].