I have recently been discussing nightmares–those frightening, upsetting dreams that disturb our sleep. I will be returning to the issue of dreams in the future but for now I would like to turn our attention to one of the most common disrupters of sleep in our society. Paradoxically, it may also be the most commonly used sleep aid as well.
I am, of course, referring to alcohol. In the past I discussed the impact of cannabis on sleep and came to the conclusion that due to lack of research we just don’t know a lot about how cannabis affects sleep. Many patients swear by it and it is becoming more available in many parts of the country. Efforts are also under way to change the status of cannabis so that more research can be conducted on it, which will be helpful. Fortunately, we know much more about the impact of our most widely used intoxicant on health in general and on sleep in particular. Unfortunately, it is pretty clear that alcohol is not a friend of those seeking good sleep.
Many people continue to believe that alcohol helps them sleep and have a few drinks as a “nightcap” before bed. It is actually easy to see why people might believe this. It is, after all, a fairly common experience for people to become sleepy after having a few drinks. A “few more” and they might even pass out. This is because alcohol has a biphasic effect on sleep and arousal. This makes it difficult to be aware of the negative effects because the positive ones come first and are more obvious.
When alcohol levels in the blood are rising or at low doses the effect is stimulatory (Lee-Chiong, 2008). This is because of the way alcohol systematically affects the brain. First affecting areas involved in the inhibition of behavior a feeling of release and activation is experienced. When alcohol levels are high or falling, a sedative effect is experienced instead (Lee-Chiong, 2008). Generally, the body can remove about 10 to 20 mg/dl per hour at a fairly constant rate (Lee-Chiong, 2008). This is primarily through metabolism in the liver. For this reason we recommend allowing 1.5 to 2 hours per drink before bedtime. This is slower than the 1 drink per hour rate that is usually discussed with regard to how quickly the body can rid itself of alcohol. By allowing all of the alcohol consumed at dinner to be removed from the body (and brain) its impact on sleep is eliminated.
When a person begins drinking, mild stimulation and pleasure may be experienced. As blood levels get higher and then begin to decrease, a sense of relaxation and sleepiness develops. This results in decreased time to fall asleep and increased deep sleep during the first half of the night. This would ordinarily be a positive effect and would make alcohol a good candidate for a useful sleep aid if the effect stopped here. Unfortunately it does not. Instead, as alcohol continues to leave the system, a rebound effect occurs and there are more arousals and awakenings from sleep. REM sleep is also increased during the second part of the night. This can result in very vivid dreams and even nightmares. In other words, the benefit given during the first part of the night is more than offset by the effect in the second part of the night. Most often this results in a poor night’s sleep and fatigue the next day. When this effect is taken to the extreme, after a night of passing out from alcohol, it contributes to the suffering known as a hangover.
I should also point out that because of the sedative effects of alcohol, snoring and sleep apnea are often made worse due to increased airway resistance caused by decreased pharyngeal dilator muscle tone. When people have seriously abused alcohol to the point of dependence the above effects become even more severe. For example, when withdrawing from alcohol, it takes longer to fall asleep, total sleep time is decreased, there are more awakenings, there is decreased deep sleep and greater amounts of REM sleep occur. After people have detoxified themselves from alcohol sleep disturbances such as insomnia can persist with deep sleep reduced, resulting in poor quality sleep, as well as reductions in total sleep time.
Alcohol has a pervasive effect on the brain with more and more effects on deeper structures with increasing blood level. A really interesting graphic on the effects of alcohol on the brain can be found here. Current thinking about relatively safe levels of alcohol consumption are for no more than 1 drink per day for women and no more than 2 drinks per day for men. And no saving up drinks for a binge on the weekend! What I concluded with regard to cannabis certainly applies even more so to alcohol–natural sleep is best.
Lee-Chiong, T. (2008). Sleep medicine: Essentials and review. New York: Oxford University Press.