How does alcohol affect sleep? If you drank like I drank a few years ago, then you’ve probably experienced the same messed-up sleep as I did.
Scientists have found that as much as 90 percent of drinkers struggle with sleep, and the script is more or less similar for most of them.
Let’s find out precisely what a good night’s sleep looks like and how it compares to a drunken one. I’ll also tell you what you can expect when you stop drinking alcohol and most importantly, just how critical your sleep quality is to your overall well-being.
Some of the health implications of chronic sleep disruption will shock you.
Stages of Sleep
So a good night’s sleep doesn’t follow a nice, straight line. Our sleep progresses in cycles. On average, each cycle lasts 90 minutes, and we go through three to five cycles a night. Each cycle has four different stages.
The first stage of light sleep lasts up to five minutes, the second stage up to 60 minutes, and the third stage, or the so-called deep sleep stage, lasts up to 40 minutes. At this stage, we’re at our most difficult to wake up.
The fourth and final stage is REM sleep, short for rapid eye movement. This is when we have dreams and one of the lighter sleep stages.
As the night continues, the REM stage occupies more and more of each sleep cycle at the expense of the other three cycles. To give you an idea, we have our first REM stage of the night around 90 minutes after we fall asleep.
And that will only last about 10 minutes. Right before we wake up, though, the last REM stage might last as long as an hour.
Drinking alcohol disrupts the relative proportions of these various stages. During the first half of the night, alcohol suppresses REM sleep. The space that would usually be REM sleep is instead occupied by deep sleep.
But during the second half of the night, these effects reverse. Light sleep in the form of REM is boosted at the expense of deep sleep.
And because we’re more likely to wake up in light sleep, drinkers tend to wake up more during the second half of the night. And there’s another reason for this, which I’ll get to shortly.
Dr. Jekyll and Mr. Hyde
This two-sided effect of consuming alcohol on sleep is a recurring theme. You get one effect during the first half of the night and its opposite in the second half.
Apart from messing up our sleep cycles, the immediate effect of alcohol is to make us sleepy. Alcohol is a central nervous system depressant. It slows the brain’s activity, leading to temporary relaxation and drowsiness.
Because of this, alcohol can shorten sleep latency or the time between when you lie down in bed and fall asleep. And as we saw earlier, drinking leads to light sleep during the night’s second half. This increases the probability of waking up.
Another reason drinkers are more likely to wake up during the second half of the night is dehydration.
Beer makers love to use images of cold beers in a bucket of ice to quench thirst. But the reality is that the more beer you drink, the thirstier you will soon become. And it’s the same for all alcoholic beverages: wine, spirits, whatever.
Alcohol has a diuretic effect. Meaning it makes us urinate more frequently. This effect is due to its suppressing an anti-diuretic hormone called vasopressin.
Without sufficient vasopressin in the system, the kidneys can’t reabsorb water into the body. Instead, they send it directly to the bladder.
This diuretic effect of consuming alcohol is so strong that we lose almost four times as much liquid as we gain through drinking alcoholic drinks.
The end result is frequent visits to the toilet. Scientists call this night-time urination nocturia. And it can obviously ruin your sleep.
A corollary of this dehydration is the hangover the following day. A hangover is simply our body’s organs taking water from the brain, desperately attempting to compensate for their water loss.
Urination also disrupts our sodium and potassium levels, which are necessary for the normal function of our nerves and muscles.
Heavy Drinking and Sleep in Numbers
Having said this, you won’t be surprised to learn that insomnia and other sleep disturbances are one of the most common health concerns of problem drinkers. Estimates for the percentage of heavy drinkers who report a persistent sleep problem range widely, from a low of 36% to a whopping high of 91%.
Most studies find a rate of around 75%. So we’re looking at roughly three-quarters of all problem drinkers suffering from poor sleep.
To make things worse, over the years, our body builds up a tolerance to alcohol’s sedative effects, which means that problem drinkers don’t even get the benefit of a deeper non REM sleep during the first half of the night.
Sleeping After Stopping Drinking
What if you stop drinking?
As you’d expect, the body needs some time to adjust. The sleep problems are magnified for the first one to two weeks after the last drink.
For example, a 2009 study with Brazilian in-patients undergoing alcohol detoxification found that 100% of women and 90% of men suffered from sleep disturbances during this time.
This acute phase of alcohol withdrawal gives way to a more moderate phase, which lasts about five weeks. Around two out of three people will experience a sleep disturbance during this time.
Why All This Matters
Sleep is a fundamental physiological process critical to our immune, hormonal, and cardiovascular systems, and better sleep equals better health.
When our sleep suffers, the entire body suffers. We all know, from our everyday life, the short-term consequences of disrupted sleep:
- Increased stress
- Emotional distress
- Cognitive deficits
- Weak work performance
- Behavioral changes, including mood swings and irritability.
In a nutshell, the day after a poor night’s sleep is one we often chalk down to the category of wasted days. This is something that we all understand.
But many people don’t appreciate the long-term consequences of disrupted sleep; in other words, all the diseases you are more likely to develop if your sleep is chronically deprived or disrupted. These include, among others:
- Hypertension and cardiovascular disease
- Impaired metabolism
- Type 2 diabetes
- Weight gain
There is also some evidence that sleep disruption and deprivation might accelerate the formation of certain tumors, leading to an increased risk of cancer.
For example, long-term data from night shift workers shows that they increase their probability of colorectal cancer by 35% in comparison with people who work regular daytime shifts.
Other studies have found that men with long-term sleep problems are twice as likely to develop prostate cancer.
Unsurprisingly, after all we’ve just discussed, long-term sleep problems are associated with higher all-cause mortality and lower life expectancy.