It's 4am. You're wide-awake. It's been another restless night.
You stare at your alarm clock in panic as the same thoughts race through your mind:
How am I going to stay awake in work tomorrow?
Why can't I just go back to sleep?!
We need sleep. Like the air we breathe and the food we eat, it's essential to our health. Without it, we wouldn't last long!
However, what is less clear is how much sleep we should be getting.
Unless you've been living under a rock your whole life, chances are you'll have heard that we should be getting eight hours' sleep every night. But is this really true?
Read on to find out how certain factors, including your age, your genes - and even cultural attitudes - play a part in determining how much sleep you really need.
Did you know that up until the 17th Century it was actually common to wake up in the middle of the night?
Roger Ekirch, a historian at Virginia Tech University, discovered a large body of evidence suggesting that humans before the Industrial Revolution slept in not one, but two chunks.
This pattern consisted of a "first" and a "second" sleep, with an hour or two of wakefulness just after midnight. It is believed that the human body has a natural preference for this segmented sleep pattern.
A relatively recent phenomenon, we now tend to sleep once within a 24-hour period. Erkirch suggests that artificial light and, sadly, cultural shifts in attitudes towards sleep as a "necessary evil" could be to blame.
It could be in your genes
Too little sleep impacts our health, wellbeing and even life expectancy.
However, research by Ying-Hui Fu at the University of California, San Francisco, has found that a small group of people naturally sleep far less than what we may consider to be typical. Known as "short-sleepers", people within this population carry a genetic mutation that reduces their need for a longer sleep.
For some people, this means sleeping for as little as four hours per night!
We change as we get older - and so does our need for sleep.
We snooze a lot as newborn babies: between 14 and 17 hours to be precise! By the time a child is school-aged, this drops to between 9 and 11 hours.
Comparatively, an older adult may only need approximately seven hours per night.
Our bodies usually know when to fall asleep and wake up.
Known as our sleep-wake cycle - or circadian rhythm - this clever internal clock helps us to feel sleepy when it's dark and alert when it's light.
Generally speaking, our sleep requirement stabilises once we become young adults, around the age of 18. At this point, we usually start following a typical sleep-wake cycle of around seven to nine hours of sleep, followed by 15 to 17 hours of wakefulness.
Quality vs quantity
Today, we can measure practically anything about ourselves. We count our steps, our calories, our exercise - and now even the time we spend catching those 40 winks!
But sometimes, we can get so hung up about quantity that we can forget about quality.
Think about how you feel when you wake up. Do you feel ready to start your day? Or are you tired and grumpy? Consider how many hours you slept for - and then try adjusting this the following night.
Ask yourself the following questions:
- Is your bedroom dark and distraction-free?
- Do you spend time relaxing before you go to bed?
- Is your mattress and bed comfortable and supportive?
- Do you try to keep to a sleep schedule by going to sleep and waking up at the same time every day?
If you can answer "yes" to every one, you're on the right track to getting good quality sleep.
We can all follow healthy habits to improve our quality of sleep - and in turn, improve our quality of life.
So how much sleep is enough?
So do we really need eight hours' sleep? In short, the answer is no.
Whilst the norm for most adults is seven to nine hours, in reality we all need different amounts of sleep to feel rested and wake up feeling refreshed.
When it comes to sleep, we are all unique. There is no "one-size-fits-all"!