No matter who you are or how much alcohol you drank, the symptoms of a hangover are pretty universal: tired, cranky, nauseous, and absolutely miserable. So, if you feel drained and without energy to even do the simplest of tasks the day after drinking, you’re not alone. But why exactly do we feel so tired after a night on the town?
It can take your body hours to get back to normal after a heavy night's drinking. Alcohol affects your sleep, so you will probably be feeling very tired and you may have to cancel plans or miss work.
While the symptoms of hangovers are common, the severity of yours will vary. The time it takes to recover will as well; some hangovers last just a few hours and others can have you feeling ill all day, or at least until you get a good amount of sleep.
When you're subject to a permanent hangover, one of the most common symptoms is having trouble sleeping. Alcohol has a dual relationship with sleep: it can make us feel sleepy initially while intoxicated and it can disturb our sleep as it wears off.
Bottom line is alcohol can seriously disrupt your sleep, leaving you jaded and making it hard to focus. And if you imbibe too much close to bedtime, both the quality and quantity of your sleep ― and your brainpower the next day ― will suffer1.
So how exactly does alcohol affect the quality of our sleep? Let's take a look at some of the reasons why it's so damn hard to sleep well after a booze fest.
#1 It causes the “rebound effect”
Even moderate alcohol consumption can ruin a good night's sleep. For instance, a modest dose of alcohol (Blood Alcohol Content in the range of 0.06–0.08) within an hour of bedtime may knock you right out — but it'll exact a serious toll on your body during the second half of your normal sleep period, during what's called a "rebound effect". But what exactly constitutes the so-called “rebound effect”?
In case you forgot, alcohol totally counts as a drug, and your body has to adjust for its effects — like the production of sleep-inducing adenosine and inhibition of the excitatory neurotransmitter glutamate— when it enters your body. After the alcohol is metabolized a few hours later, these adaptations are now unnecessary2, and your body is all out of whack. Needless to say, this can jolt you awake.
#2 It prevents deep sleep
The stage associated with dreams and learning, REM sleep is one of the most restorative parts of sleep3 - and it's reduced by alcohol.
Recent research shows that our dreams may play a crucial role in maintaining the normal function of human physiology and brain function. That’s because during REM, certain neurotransmitters like serotonin are effectively switched off, so we use this period of our sleep to replenish or reset these vital brain chemicals.
While low and moderate doses of alcohol seem to have little effect on REM sleep, high doses of alcohol have a significant impact on the amount and duration of REM.
In other words, not only are you more likely to wake up thanks to the rebound effect, but you're also missing out on the most restorative stage of shut-eye. This can leave you feeling tired the next day no matter how long you stay in bed. No wonder hangovers make you feel tired, sluggish and stressed.
#3 It interrupts sleep for trips to the bathroom
When you drink more than usual, you may often have to get up in the night to go to the toilet. That’s because alcohol is a potent diuretic4 and makes you urinate more than you would when drinking the equivalent volume of non-alcoholic drinks. According to one study, for every 1g of alcohol drunk, urine excretion increases by 10ml5.
The reason this happens is because alcohol suppresses a hormone known as vasopressin (anti-diuretic hormone) which regulates the amount of water absorbed by the kidneys. When vasopressin is low, instead of storing water, the kidneys dump it into the bladder, causing the urge to pee.
This creates a very strong urge to make repeated trips to the bathroom – making for some potentially very sleepless nights.
#4 It affects women more
A 2011 study6 into the effect of intoxication on healthy young adults found that alcohol disrupts sleep in women more than in men.
These gender differences could be explained by the fact that women metabolize alcohol more quickly than men, meaning that the sedative properties of a late-night drink wear off more easily, causing women to feel the second, more fragmented part of their sleep more quickly.
In summary, this study found that women had fewer hours of sleep, woke more frequently and for more minutes during the night, and had more disrupted sleep than men.
A 2013 review of 27 published studies found out that alcohol reduces the time it takes to fall asleep and increases the amount of deep sleep during the first half of the night. However, this is offset by increased sleep disturbances in the second half of the night7.
Overall Hangovers Get You Tired
So, if you plan on downing more than one drink, you're looking at some pretty serious bedtime disturbance. And that’s mainly because alcohol is very disruptive to sleep.
Although many people may feel alcohol helps them get off to sleep, it is also a major culprit for disrupting your night as it can interfere with the body’s chemical processes needed for sound sleep. Waking up deprived of the vital sleep your body needs will leave you feeling drained.
For a healthier day