So how do you know if you are getting enough sleep? Research from Britain and the USA has found that more than one in four adults feel they suffer three bad nights of sleep each week.
ON a very simple level, it does depend on how you feel - poor sleep will leave you feeling tired and sluggish the following day - though there are other tests you can do to see if you have a more serious sleep problem.
First, let's look at a 'normal' day.
Our lives are governed by an internal 'clock' that sets out the rhythm of peaks and troughs we experience during the day.
This clock is called the 'circadian rhythm' and it governs everything from hormone production to when we feel like going to bed.
We are all at our most sleepy in the early hours of the morning and again in the early afternoon, which might be why work can seem like a chore just after lunch.
The circadian rhythm doesn't work alone however, it works along with other factors, such as light - light can actually reset our clock, for example when we travel through time zones.
Through the release of the hormone melatonin, our internal clocks start gently telling our body, a few hours before we go to bed, that sleep is approaching.
By releasing the stress hormone cortisol into our bloodstream, our internal clock also prepares us for the new day a few hours before the alarm sounds.
For our body clock to get the release of hormones correct, light is essential.
This is why the glare from a street light invading your bedroom can make it hard to sleep - you might know it's night-time, but your body can't tell the difference between electricity and the sun.
So, if you feel perky in the morning, a little sluggish after lunch and then more alert in the evening, you are probably getting your sleep balance right.
However, if you dread the sound of the alarm and spend the morning in a daze, tetchy and distressed, and you find yourself suffering from frequent colds and viruses, you are probably sleep deprived.
There can be a large number of reasons for this, such as: •Birth of a new baby •Menopause •Pressure at work •Overactive thyroid gland •Post-traumatic Stress Disorder •Anxiety •Bereavement •Illness •Depression •ME or Chronic Fatigue Syndrome •Shift work •Penchant for late night parties •Overuse of stimulants such as coffee, alcohol and nicotine •Sleep apnoea (breathing difficulties that cause you to wake repeatedly) •Snoring partner •Jet lag •Delayed Sleep Phase Syndrome (DSPS), making it impossible to fall asleep until early morning •Ageing It may even be the short term, regular effects of another cycle; premenstrual syndrome is known to cause sleeplessness.
Although chronic sleep deprivation (which means you are literally falling asleep during the day) can be rectified over a couple of nights, a slow build up of sleep loss, even an hour or so a night, can affect your long-term health and make you susceptible to illness, weight gain and even premature death.