Contrary to prevailing thought, alcohol promotes sleep by affecting homeostasis rather than circadian rhythms. So should drinking be used as a sleep aid?
Alcohol induces sleep disruptions by interfering with sleep homeostasis, not by changing circadian rhythms, according to a new study.
“The prevailing thought was that alcohol promotes sleep by changing a person’s circadian rhythm-the body’s built-in 24-hour clock. However, we discovered that alcohol actually promotes sleep by affecting a person’s sleep homeostasis-the brain’s built-in mechanism that regulates your sleepiness and wakefulness," said Mahesh Thakkar, PhD, Associate Professor and Director of Research in the University of Missouri School of Medicine Department of Neurology, in Columbia.
Alcohol is a potent somnogen and one of the most frequently used “over-the-counter” sleep aids. In healthy nonalcoholics, acute alcohol intake decreases sleep latency and consolidates and increases the quality and quantity of non–rapid eye movement (NREM) sleep during the first half of the night. However, sleep is disrupted during the second half of the night, the researchers reported.
Alcoholics, both during drinking periods and during abstinences, experience a multitude of sleep disruptions manifested by profound insomnia, excessive daytime sleepiness, and altered sleep architecture.
Over the past 5 years, the researchers have conducted a series of experiments using animal models. They have found that the sleep-promoting effects of alcohol may be mediated via alcohol’s action on the mediators of sleep homeostasis.
Sleep homeostasis balances the body’s need for sleep in relation to how long a person has been awake. If a person loses sleep, the body produces adenosine, a naturally occurring sleep-regulating substance that increases a person’s need for sleep. When a person goes to sleep early, sleep homeostasis is shifted and he or she may wake up in the middle of the night or early morning.
The researchers found that alcohol alters the sleep homeostatic mechanism and puts pressure on a person to sleep. When this happens, the sleep period is shifted, and a person may experience disrupted sleep.
Their results also suggest that disrupted sleep homeostasis may be the primary cause of sleep disruption observed after binge drinking.
“Based on our results, it’s clear that alcohol should not be used as a sleep aid,” said study author Pradeep Sahota, MD, Chair of the University of Missouri School of Medicine Department of Neurology. “Alcohol disrupts sleep and the quality of sleep is diminished. Additionally, alcohol is a diuretic, which increases your need to go the bathroom and causes you to wake up earlier in the morning."
In addition to studying alcohol’s impact on sleep homeostasis, the researchers explored how alcohol withdrawal affects sleep. They found that after extended periods of frequent drinking, subjects would fall asleep as expected but would wake within a few hours and would be unable to fall back asleep. When the subjects were not given alcohol, the researchers found that subjects showed symptomatic insomnia.
“During acute alcohol withdrawal, subjects displayed a significant increase in wakefulness with a reduction in rapid eye movement and NREM sleep,” Dr Thakkar said. “This caused insomnia-like symptoms and suggests an impaired sleep homeostasis.”
The researchers published their results in the November 11, 2014 online edition of the journal Alcohol.