We all know sleep deprivation isn't great for us, but we might not always pick up on the signs that we're suffering from it.
This year's World Sleep Day, falling on Friday 17 March, is the perfect reminder that all adults need between seven and nine hours of shut eye each night to function at our best. And perhaps more importantly, this should be undisturbed and comfortable, allowing your body to fully recover.
But for those of us who lead busy lives and struggle to prioritise sleep, what exactly can happen to us physically and mentally? Sleep expert Dr Katherine Hall of Happy Beds brings the harsh reality to life...
The five warning sigs you're not getting enough sleep
1. Your skin is paler and sallower
Yes, you won't just feel groggy, you might start to look physically unwell too.
"Over time, without proper sleep, skin can become paler and sallower, lacking in the usual healthy colour you'd expect. Furthermore, the skin will begin to sag and possibly even wrinkle, especially around the eyes," says Dr Hall.
"A couple of nights without great sleep shouldn't lead to this; however, these effects will start to become more obvious over an extended period."
2. Your eyes are red and puffy, and you have dark circles
What might be more concerning, is that regularly having tired eyes can lead to premature ageing.
"We're probably all familiar with the feeling of looking in the mirror after a poor night's sleep and seeing the telltale signs in our eyes. We begin to suffer from red and puffy eyes relatively soon after our period of poor sleep starts," explains Dr Hall. "Dark circles also appear around our eyes and lines start to build over time."
3. You’re feeling low
Feeling consistently low due to poor sleep isn't something to be brushed off, as it can lead to more serious problems.
"It's not just the eyes and skin that are affected by a lack of sleep; physical appearance is also hugely altered by mood," points out Dr Hall.
"We're all familiar with that feeling when the alarm goes off, and we've had a bad night's sleep – we're moody and miserable, feeling down and even anxious. These are all common effects, sometimes even leading to mental health problems."
4. You’ve put weight on
You may have no idea that sleep deprivation is to blame, but it's "quite common" for weight gain to be linked to a sleep deficit.
"The NHS advises that studies have shown that people who sleep less than seven hours a day tend to gain more weight and have a higher risk of becoming obese than those who get seven hours or more," adds Dr Hall.
Naturally, when we are tired we find it harder to stick to healthy balanced eating as we crave more comfort food and energy. While of course this is okay in moderation, it's not great long-term health-wise.
5. You keep getting the common cold
Our body needs to be well-rested to fight off infection.
"A prolonged lack of sleep can negatively affect the immune system, enabling these sorts of illnesses to creep in more often," says Dr Hall.
How to prevent sleep deprivation
The reality is, that it can often feel hard to prevent ourselves from suffering from sleep deprivation in the first place, when it feels like there are other more important things to do.
"So many people deprive themselves of sleep through sleep procrastination and staying up too late to 'get things done' – either finishing work, doing personal chores around the house, or having 'me time'," explains sleep expert Tracy Hannigan, aka Tracy The Sleep Coach. "Just as the physical sleep cycle starts when we wake up in the morning, so does the prevention of sleep procrastination."
But, while you might not think there's anything you can do about it, Hannigan suggests some simple but effective changes to make.
"Prioritising tasks, saying yes and no appropriately, and leaving time for oneself in small ways throughout the day can help organise our logistical and emotional lives so that we can begin to wind down for sleep after the day is over," Hannigan recommends.
"To help with this, creating rituals around the 'closing of the day', such as no laptops after dinner, and no phones in bed – and instead doing something we enjoy – can help us leave the day behind and get better quality sleep."
How to sleep better not just longer
While getting the recommended amount of hours a night is ideal, Hannigan emphasises that sleep quality is more important to our ability to concentrate and feel good during the day.
"Sleep quality is affected primarily by the building of 'sleep drive'. This can be improved by two things: the length of time we are awake/starting the day (vs laying around in bed) and how physically active we are," she says.
"A person who sleeps eight hours and has a sedentary job and no extra exercise builds less sleep drive than a person who sleeps eight hours and has a more active day. Now, both people might be fine, but the first person would be more susceptible to sleep disruption as they would be closer to a threshold point where arousal and wakefulness are closer to having an impact on their sleep."
It seems sleep drive and psychological arousal need to be in balance. "So learning to rest and relax and manage stress can help improve balance with sleep drive and promote deeper sleep," she adds.
What to do if you've slept badly
Lets face it, sometimes we're going to sleep badly, which is less than ideal when we have no choice but to get up for work the next day. But it's how we deal with it that matters.
"For people who have slept badly and have to get going in the morning, fatigue management after a bad night can be tackled in several different ways," Hannigan points out.
"First, have a cold blast in the shower before dressing, even if you take showers at night. The cold water can invigorate you, and you will have a rush of hormones that will help you feel more alert, and more vibrant. It also can help reduce any redness in your eyes.
"A. brisk walk (maybe on the way to work) can also help build energy. Eating a breakfast rich in vitamins, such as a protein and complex carb, can help top up your energy levels till lunch where – if you have a chance – a 15-minute nap can help reduce sleepy feelings."
In a nutshell, mentally focussing on things other than tiredness and taking healthy measures to help re-energise your body throughout the day will get you through.
Hannigan adds, "In the evening, if you can, stick to your regular bedtime as that would be helpful in the long run. But if your poor sleep is very intermittent, it won't be a problem to go to bed half an hour earlier than usual to get a bit of extra sleep."
Watch: The science behind beauty sleep