Many insomniacs take a drink of whiskey or wine before bedtime in order to reduce sleep latency. While alcohol does help people get to sleep faster, drinking has been shown to result in low quality of sleep as measured by nighttime awakenings (fragmented sleep) and decreased time spent in REM sleep.
After a few drinks, especially in people who don’t drink much, individuals often report subjectively shallow sleep and frequent mid-night awakenings. The effects vary greatly; some people experience sweating (a monkeywrench in the body’s sleep thermoregulation process) and vivid dreams (a characteristic of abrupt transition between stages). Indeed, drinking lowers your body’s core temperature slightly, followed by a rise. In controlled studies with EEG monitoring, researchers have found that REM is supressed early in the nighttime, but that the REM rebound can occur in the second half of the night.
At low doses alcohol has GABA agonist properties – just like most insomnia medications do.
The mechanism by which alcohol suppresses REM sleep is not clear. It does not seem to interact with the neurotransmitter adenosine, which known to be important in REM. It seems probable that alcohol’s general depressant properties reduces brain activity that becomes active in REM. Alcohol does inhibit the neurotransmitter glutamate’s entry to NMDA-receptors (one of the brain’s receptors for glutamate) and glutamate is the main excitatory neurotransmitter, so this provides a partial explanation for alcohol’s effect on general brain activity.
Sleep-disordered breathing, a dyssomnia affecting millions of people, is made worse by alcohol.
There's a connection between obstructive sleep apnea and alcohol consumption. Drinkers can experience apnea if only for a night. Alcohol impairs breathing in sleep by relaxing the throat muscles and it affects the brain's breathing center by masking the effect of low oxygen levels in the bloodstream, possibly damaging tissue. Even people who normally don't snore do so if they have been drinking the night before. Snorers without apnea can exhibit apnea symptoms if they have been drinking. Hangover symptoms - attributed to the efforts of the body to metabolize alcohol - are frequently partially due to breathing-disordered sleep.
Detailed studies of sleepers’ EEG readings have found that the alcohol disrupts sleep differently in the first half of the night than in the second half. (http://www.nature.com/npp/journal/v20/n3/full/1395251a.html)
Alcohol tends to be metabolized rapidly, so halfway through the night the concentration of alcohol in the bloodstream is down to approximately zero. The metabolites are still around and the effects of the alcohol persist (that’s where hangovers come from). But alcohol per se doesn’t directly affect sleep architecture during the second half of the night. The discomfort people may feel when they awaken during this period could be due to withdrawal/hangover. This is not to say that sleep cures drunkenness or tipsiness. Indeed, the military has shown that young adult pilots suffer detrimental effects on their motor skills and flying ability the day after drinking the previous evening.
Alcohol dependence and sleep disorders are often co-morbid – people suffer both at the same time.
There is also the causal arrow running in the opposite direction. People who don’t get a good night’s sleep and are tired during the day may be more apt to drink in the evening.
A 1999 poll found 28% of American insomniacs used alcohol to get to sleep. Insomniacs are more likely to drink before bedtime than good sleepers - the alcohol can be considered self-medication. Alcohol is a constituent in over-the-counter medical preparations like Nyquil – partly to dissolve the other medicines better than water can and partly because alcohol is a relaxant and depressant and the makers know it will help some patients fall asleep. (Nyquil contains an antihistamine to help patients stay asleep through the night.).
Knowing alcohol’s ability to cut sleep latency times, insomniacs could be more likely to take a drink before bed – self medicating with whatever is in the liquor cabinet. Maybe this works as a short-term fix, but for most people it is not a long-term solution. Frequent alcohol use can lead to a dependency – maybe not alcoholism but the body anticipates a drink every night – and the alcohol changes the sleep cycle, to which the body compensates – some.
There is some evidence that in general men and women react to alcohol differently. A study on young adult women showed alcohol increased their time in deep sleep, while cutting REM sleep. Men, on the other hand, experience a decreased in both deep and REM sleep after drinking. These are very general trends, and individuals differ widely in their reactions.
A more recent study found women’s sleep is MORE affected by alcohol than men’s.
Insomnia and alcoholism can both be chronic conditions and often co-morbid.
Sleep fragmentation and difficulty in maintaining sleep (DIS) are common in alcoholics – both those who drink and those who are trying to quit. Sleep problems are often experienced by people who cut back on their alcohol consumption. Alcoholics in recovery programs have to remember this. Insomnia is a withdrawal symptom.
In fact, poor sleep and the discomfort it brings is thought to be a major reason for relapse among alcoholics trying to quit.
Changes in sleep architecture and the advent of sleep disorders can predict relapse in alcoholics who have quit drinking. Researchers have documented a relationship. Perhaps if in the future widespread home monitoring of sleep patterns will enable recovering alcoholics or their family members to be forewarned about a possible relapse.
Quitting drinking may not bring a return to normal sleep. Chronic alcohol consumption disturbs the function of calcium channels in the thalamus, which is part of the brain involved in sleep regulation. A Wake Forest University study found “the brain adapts to long-term alcohol use and doesn’t immediately return to normal when alcohol use is stopped.” ( http://www.eurekalert.org/pub_releases/2004-10/wfub-nfc101804.php)
Alcoholism, or a propensity to consume alcohol, has some genetic basis. A tendency to insomnia can also has be in-born, although it is incorrect to call insomnia an inherited condition. Scientists have found the PER gene has a polymorphism and the PER3 form is associated with both night owlness and decreased sleep quantity. This PER3 phenotype has been found to predict insomnia in alcoholics.
AARP Blog - Say No to a Nightcap: It’s Bad for Your Sleep