How alcohol ruins your sleep quality

  1. Author: Conor Erb
  2. Date: July 7, 2021

Sleep is essential if we are to function properly. Lack of sleep doesn’t just mean we feel weary the next day, it leaves us struggling to concentrate or think clearly. Everything seems more difficult to do or to understand, making decisions can feel like an impossible task, our judgement is affected and we can suffer from uncharacteristic mood swings. It impacts on work performance and how we carry out day-to-day tasks, like driving.

Adults generally need between seven and nine hours of good quality sleep per night. We sleep in cycles roughly lasting between ninety minutes and two hours, during which we rotate through stages that take us from light slumber, to deep sleep, to deep REM (rapid eye movement) sleep, which is when we generally dream.

The most common causes of poor sleep include:

  • stress, anxiety or depression
  • noise
  • discomfort – room temperature or uncomfortable beds
  • alcohol, caffeine or nicotine
  • recreational drugs
  • jet lag

Some of those are things we have little or no control over – external triggers can cause stress, an inconsiderate neighbour might play music or the television too loud into the early hours. Others, however – such as temperature and what we consume – are within our control.

One too many

We probably all know how it feels to wake up after one (or more than one) too many alcoholic drinks. We feel sluggish and slow, tired, thirsty, brain-fogged. We certainly don’t perform at optimum level, often losing a morning, and sometimes the whole day, to feeling less than our best. We may have slept like a log all night long, and yet we feel as though we’ve had no rest.

That’s because it’s not just sleep that we need; we need good quality sleep.

There’s a hard-to-shift belief that having an alcoholic drink or two – not necessarily drinking to excess – is a sure-fire way to get a good night’s sleep. Many people rely on it. However, while having a drink might knock you out, the quality of your sleep is likely to be less than good. And, as we’ve established, it’s the quality of your sleep that is key to waking refreshed and ready to face the day ahead.

How alcohol affects sleep

First up, it’s not a myth – alcohol will help you get to sleep. However, it’s unlikely to help you have good quality sleep, and your sleep later in the night will probably be disrupted as your body deals with the alcohol in your system.

Alcohol is a diuretic, so you wake to go to the bathroom through the night. That often results in dehydration, which causes a headache, and sometimes muscle cramps, and the pain can wake you.

Alcohol also raises your body temperature, meaning you can wake up overheated and uncomfortable.

Do you find you snore when you sleep after drinking alcohol, even if you generally don’t? That’s because alcohol is a muscle relaxant. Snoring can impact on your quality of sleep and also lead to you waking up with a sore throat.

We mentioned sleep stages earlier. Alcohol disrupts the body’s natural cycling through these stages, meaning sleep is less beneficial. While it initially acts as a sedative, putting you into deep sleep when you first go to bed, as the effects wear off your sleep becomes lighter and the chances of waking are increased, which reduces overall sleep time.

Alcohol also appears to suppress mentally restorative REM sleep, which can affect memory and cognition.

The homeostatic drive

The longer we are awake, the greater the urge is to go to sleep. This is known as the homeostatic drive and it’s a key regulator of the sleep-wake cycle. It works by increasing levels of adenosine during our periods of wakefulness, meaning we should be ready to sleep at bedtime. The body breaks down adenosine as we sleep and it all starts again the following day. Alcohol boosts adenosine in the system, meaning we plunge into a deep sleep. However, in a bid to balance deep sleep and lighter sleep, we get less deep sleep in the second half of the night.

The circadian rhythm

Our natural body clock has a repeating rhythm that typically runs on a 24-hour cycle. An element of this circadian rhythm is that melatonin is released to prepare us for sleep in the evening. Drinking alcohol lowers melatonin levels, which has an impact on sleep quality.

Cortisol and glucose production

Alcohol consumption triggers an increase in cortisol, the stress hormone. It’s usually produced as part of the body’s stress response system and in the short-term can be helpful – it increases alertness, for example. However, it can also increase blood pressure, and adversely affect processes such as digestion and sleep.

Blood sugar levels rise at night as part of the circadian rhythm. Good quality restorative sleep can actually reduce blood sugar levels, if they are too high.

Cortisol production is increased by sleep deprivation and drives glucose levels up. People with higher blood glucose experience poorer sleep.

It can be a vicious cycle

Heavy alcohol use makes insomnia worse, and there’s a danger of falling into a destructive cycle of using alcohol to sleep, experiencing poor-quality sleep that leaves us tired the next say, so using caffeine to perk up, then needing alcohol again as a depressant to combat the effects of the caffeine.

Just the one!

Assuming not everyone wants to stop drinking entirely, how can we drink in such a way that we enjoy ourselves, but don’t impair the quality of our sleep?

A 2018 study found that even low amounts of alcohol decreased sleep quality by over 9%. Moderate amounts had a 24% impact and high (classed as more than two servings per day for men or more than one serving per day for women) decreased sleep quality by over 39%.

To reduce the risk of sleep disruption, the Sleep Foundation recommends that you stop drinking alcohol at least four hours before bedtime, which allows your body time to metabolise the alcohol. If you take a relaxing herbal tea or a milky drink before bed, that can also help you to sleep better.

If you struggle to get a good night’s sleep, you’re not alone; a Google search on ‘how to get a good night’s sleep’ brings up almost 67 million responses. There’s a range of options open to you if you are looking to improve the quality of your sleep – and swapping to low- and no-alcohol drinks is a powerful change for the better that you can easily make.

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