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Think a nightcap may help you get a better night’s sleep? You are wrong!

Anyone who consumes alcohol from time to time knows that drinks like beer, wine, or spirits can leave you feeling drowsy. Due to this effect, many people started to use alcohol as a sleep aid. In fact, surveys show that as many as 20% of Americans use alcohol to help them fall asleep in the evening. Alcohol is a depressant, and it indeed induces sleep. However, it also contributes to poor quality shuteye, leading to interrupted snoozing, night sweats and disturbed REM sleep. [1]

Watch this video to learn what happens behind your closed eyes when you go to sleep after drinking.

Alcohol Doesn’t Aid Sleep

A study conducted in 2013 and published in Alcoholism: Clinical & Experimental Research has proven that alcohol doesn’t aid sleep.[2] Although it reduces the time required to fall asleep (sleep onset latency), it causes disrupted sleep in the second half of the night, by increasing non-REM sleep and reducing rapid eye movement.

Depending on the amount of alcohol you consumed, what seems like falling asleep will more likely be closer to passing out. Tolerance for the sedative effects of alcohol is quickly built, which means that over time you will have to drink more to enjoy the same sleep-inducing effects of alcohol consumption.[3]

Since alcohol is quickly metabolized, most people experience withdrawal symptoms in the second half of the night. Symptoms of withdrawal may include shallow sleep and multiple awakenings, REM rebound associated with nightmares or vivid dreams, sweating, and general activation.

Using alcohol as a sleep aid may not only lead to dependence, but also cause a variety of sleep problems such as sleepwalking, sleep talking, and sleep deprivation.

Lastly, alcohol also suppresses breathing and can precipitate sleep apnea. Since alcohol impairs sleep during the second half of the night, it reduces overall sleep time which leads to daytime somnolence.

The Relationship between Alcohol and Insomnia

Insomnia is often a chronic condition, and relying on alcohol to fall asleep will only make things worse and increase your risk of alcohol dependence. Alcoholism itself is associated with the complaints of poor sleep, increased sleep onset, sleep maintenance issues, and decreased delta and REM sleep.[4]  Lastly, it increases the severity of obstructive sleep apnea, even in individuals without a history of OSA.[5]

How Does Alcohol Interrupt Sleep?

According to a study by Wayne State University and the National Institute on Alcohol Abuse and Alcoholism, after a few drinks, individuals report subjectively shallow sleep and frequent awakenings in the middle of the night.[6]

Research shows that, in the first half of the night, when the body is metabolizing alcohol, people spend more time in deep, slow-wave sleep and less time in REM sleep. REM sleep is a vital sleep stage for physical and mental restoration. This is why after a night of drinking, you wake up in the morning feeling drowsy and tired, no matter how long you stay in bed.

You probably think it’s great to spend more time in deep sleep, but it’s really not healthy for you. Why? Because our sleep architecture is biologically tuned to meet our body’s needs during sleep. Abrupt changes to our typical and natural structure of sleep aren’t generally good for our wellbeing.

During the second half of the night, sleep becomes even more disrupted. As alcohol is metabolized and its sedative effects start to disappear, the body goes through a process the experts call a rebound effect[7]. The rebound effect includes a sudden change from deeper to lighter sleep, with more frequent awakenings during the second half of the night. The abrupt frequent awakenings can manifest as micro-awakenings that you don’t even remember, but they still interrupt the natural flow of sleep and its quality. Our sleep architecture shifts again, and we spent significantly less time in slow wave sleep. The rebound effect may also include more time in REM sleep, which is characterized by vivid dreaming. Disrupted REM sleep also Increases risk for parasomnias including sleepwalking and sleep eating.[8]

Mid-night awakenings after drinking are common because alcohol affects the normal production of chemicals in the body that induce sleep (such as melatonin and ATP) when you’ve been awake for a long time, and recede once you’ve had enough rest. After drinking, production of adenosine (vital for inducing sleep) is increased, allowing for a fast onset of sleep. But it recedes as quickly as it came, making you more likely to wake up before you’re truly rested, and preventing you from falling asleep again – another consequence of the rebound effect.

Simply explained, alcohol’s adenosine-boosting effects mess up with your internal sleep drive and make you sleep at times other than you would naturally, throwing your natural sleep-wake cycle off course.[9]

This is the primary way alcohol disrupts sleep, but the effects of going to sleep with alcohol in your system don’t stop here. Here are other ways how alcohol interrupts nightly rest.

Disrupted sleep-wake cycles

Alcohol suppresses melatonin, the primary regulator of sleep-wake cycles. Research shows that a moderate dose of alcohol just 1h before bedtime can decrease melatonin production by 20%.[10] Alcohol reduces the ability of the master biological clock to respond to the light which helps it to stay in sync with the 24h day/night cycle.[11]

Effects on circadian rhythm

Let’s quickly refresh our knowledge on the importance of the body’s internal clock. Our 24-hour rhythms are managed by the master biological clock which is responsible for coordinating circadian rhythm activity through the body.

Circadian rhythms are crucial for our health because they regulate nearly all of the body’s processes, from metabolism and sleep to immunity, energy, our sexual drive, cognitive functions, and mood. Alcohol disrupts circadian functioning and directly interferes with the ability of the master biological clock to synchronize itself. Since our internal clock is, as we previously mentioned, responsible for regulating all of the major body’s processes, the disruptive effects of alcohol can be widespread, affecting not only our sleep, but other systems as well, resulting in poor liver function, leaky gut, and depression.

  1. Poor liver function – Our liver is the body’s filtering system, and its primary role is to metabolize food and chemicals (including alcohol) and to remove toxins from the bloodstream. When alcohol disrupts the circadian rhythms regulating the liver, it compromises liver function and contributes to liver toxicity and disease.
  2. Leaky gut – The gut and its microbiome are often referred to by experts as the body’s second brain, and it’s also operated by circadian rhythm activity. When thrown out of sync, the lining of the gastrointestinal tract becomes more susceptible to permeation, meaning the lining of the GI tract is more likely to allow bacteria, and toxins to leave the intestines and enter the bloodstream.
  3. Depression – There’s a complicated relationship between depression, alcohol, and sleep. Depression and insomnia are often comorbid, and even the presence of moderate amounts of alcohol may make things even worse, especially when it comes to further pushing your circadian rhythm out of sync.

Diuretic effect

Your body knows that nighttime is time for sleep, and not adequate time for trips to the bathroom. Simply explained, your body has learned to put your bladder into hibernation for the night. But alcohol, since it has a diuretic effect, will cause you to wake up to use the restroom during the night, and interrupt your sleep.

Night sweats

Drinking affects your sleep homeostasis by messing up with the body’s core temperature. Alcohol first cools you down, helping you to fall asleep, but in the second half of the night, your body temperature will rise. Due to alcohol’s diuretic effect, your body will be encouraged to lose the extra heat through sweat, ultimately making you dehydrated. Night sweats may be particularly problematic for people who already sleep hot. However, once the effects wear off, your body counteracts it with a corresponding rise in temperature, causing night sweats and making you wake up earlier than expected.

Snoring and sleep apnea

Alcohol relaxes all the muscles in your body, which means that the relaxed tissue in your throat, mouth, and nose may stop proper air flowing, causing the air to vibrate, and resulting in loud snoring.

Effect on sleep disorders

Research shows that alcohol consumption may lead to the development of new sleep disorders or make existing ones worse, particularly when it comes to insomnia[12] and OSA (obstructive sleep apnea).[13]

As you can see, alcohol can equal a fitful night’s sleep. Sleep and circadian rhythm interference from alcohol contribute to next-day sleepiness, fatigue, irritability, and difficulty focusing. Even if you don’t experience it as a typical hangover, alcohol-related sleep loss negatively affects your mood and performance during the day.

The Bottom Line

The bottom line is that the more you drink, and the closer it is to your bedtime, the more it negatively affects your sleep. It doesn’t matter if you take moderate amounts of alcohol at bedtime. Almost any quantity can alter your sleep architecture and natural sleep flow.

Alcohol may severely affect your sleep, but that doesn’t mean you should stop consuming it completely. So, you may be wondering how much alcohol is too much for sleep?

Ideally, you should drink 2 to 3 times a week. This gives you enough room to enjoy a glass of fine wine at your favorite restaurant, an evening cocktail with your friends, and a cold beer at home after a busy week – without interfering with healthy sleep.

And when is the best time to consume alcohol?

Circadian rhythms affect how the body responds to alcohol, depending on the timing of alcohol intake. Research shows the body metabolizes alcohol differently at different times of the day. Your body is least prepared to process alcohol in the morning, and best metabolized early to middle evening hours – or during the traditional “happy hour” time.

Resources and references

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4666864/

[2] https://onlinelibrary.wiley.com/journal/15300277

[3] https://pubs.niaaa.nih.gov/publications/arh25-2/101-109.htm

[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2775419/

[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5840512/

[6] http://grandchallengesforsocialwork.org/wp-content/uploads/2015/12/WP14-with-cover.pdf

[7] https://en.wikipedia.org/wiki/REM_rebound

[8] https://pubs.niaaa.nih.gov/publications/arh25-2/101-109.htm

[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5821259/

[10]https://www.researchgate.net/publication/291450048_An_interaction_of_melatonin_with_alcohol_A_case_study

[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2778757/

[12] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2775419/

[13] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5840512/

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