News & Views

How drinking alcohol affects sleep

By Zach Pearl, PhD Staff


Alcohol tricks people into thinking they are getting better sleep. Indeed alcohol might help fall asleep faster but even just a couple of drinks can affect the quality of sleep. Someone that is drinking regularly, may find himself awaken the next day feeling like he hasn’t had any rest at all. 6

What alcohol does while sleeping?

Alcohol reduces melatonin levels

Melatonin is a sleep hormone and has acute, sleep-promoting influences in humans. On its absence people may suffer from sleep problems1. A recent study concluded that alcohol affects the biological clock’s timing, causing “desynchronization”2. Other studies demonstrated that there is a melatonin suppression in the body several hours after acute alcohol consumption3 4.

Alcohol affects sleep patterns

Even a couple of drinks can interfere with the normal sleep process and the more one drinks before going to bed, the more pronounced these effects are. According to the findings, although alcohol allows healthy people to fall asleep quicker and sleep more deeply for a while, it negatively affects the second half of the night5. Most individuals who have few drinks prior to bedtime will suffer withdrawal symptoms during the second part of the night, as alcohol is metabolized rapidly and its blood concentrations in one’s body are negligible by then6. Alcohol consumption before sleep can cause increased arousals and multiple awakenings, REM rebound, reduction in slow wave sleep nightmares or vivid dreams, sweating, and general activation during the second half of the night6. Disruptions in REM sleep may cause daytime drowsiness, poor concentration and fatigue. Alcohol also results in excessive daytime sleepiness7 and clinicians have been advised to warn patients who are concerned about daytime sleepiness to limit their alcohol intake6.

Alcohol causes breathing problems

Approximately 2%-4% of Americans suffer from obstructive sleep apnea (OSA), a disorder in which the upper air passage narrows or closes during sleep8. Alcohol was found to worsen snoring and exacerbate obstructive sleep apnea9. It impairs breathing during sleep by relaxing the throat muscles and affects the brain’s breathing center by masking the effect of low oxygen levels in the bloodstream, possibly damaging tissue. In addition, it prolongs the time required to arouse or awaken after an apnea occurs10. 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 – caused by the efforts of the body to metabolize alcohol – are frequently partially due to breathing-disordered sleep.

Alcohol causes nightmares, sleep walking and leg movement problems

Alcohol may increase nightmares, arousal disorders, and increased restless legs syndrome (RLS) symptoms (people with RLS have uncomfortable sensations in their legs or arms and an irresistible urge to move the legs to relieve the sensations)11. People who consume two or more drinks per day have 2-3 fold increase in RLS that fragments sleep12. Alcohol may also provoke sleepwalking, especially when taken in combination with sedative drugs (e.g. traditional hypnotics)13. Lastly, frequent awakenings during the second half of the night may lead to un-steadiness and falls during nighttime trips to the bathroom. The elderly are at particular risk, as they achieve higher levels of alcohol in the blood and brain than younger persons after consuming an equivalent dose. Bedtime alcohol consumption among older persons may lead to un-steadiness if walking is attempted during the night, with increased risk of falls and injuries14.

In conclusion, alcohol is a commonly used substance for sleep induction. However, it is a poor choice as a hypnotic because it can disrupt sleep even further, may lead to alcohol dependence and alcoholism, and may intensify sleep-related breathing disturbances.

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