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 streetlight invading your bedroom can make it hard to sleep – you might know its 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
- Pressure at work
- Overactive thyroid gland
- Post-traumatic Stress Disorder
- ME or Chronic Fatigue Syndrome
- Shift work
- Penchant for late-night parties
- Overuse of stimulants such as coffee, alcohol and nicotine
- Sleep apnoea (a breathing difficulty that causes you to wake repeatedly)
- Snoring partner
- Jet lag
- Delayed Sleep Phase Syndrome (DSPS), making it impossible to fall asleep until early morning
Most of us do more than just sleep in bed. How we spend time in the bedroom also changes constantly throughout our lives.
It may even be the short-term, regular effects of another cycle; premenstrual syndrome (also known as premenstrual tension) is known to cause sleeplessness.
Although chronic sleep deprivation (which means you are literally falling asleep during the day, and which can even be caused by missing a single night of sleep) can be rectified over a couple of nights, a slow buildup 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.
HOW SLEEP WORKS
While we are still unclear about the exact role of sleep, scientific research has revealed more about the form it takes. Sleep has two main states – REM (Rapid Eye Movement) and non-REM.
Within the non-REM stage there are four distinct stages. The first stage is very short, lasting about 10 minutes. It allows the muscles to relax and the brainwave patterns begin to slow down. During this stage you are very easy to wake, and as it begins, you may have that sensation of ‘nodding off’, with little rouses into consciousness.
To an observer, stage two looks very much like stage one, however an EEG (a graph called an electroencephalogram that depicts the pattern of brain waves produced by the brain) shows that there is a change in the type of brain waves being produced.
A single wave, called K complexes, is followed by a sleep spindle (named after the spindle shape it makes on the EEG screen). It would take a louder noise or firmer prod to rouse you from this stage, but you are still considered to be in the ‘entering’ stage of sleep.
About 10-1 5 minutes after the onset of stage two, you enter stage three. The brain waves are now slow and make rolling shapes on the EEG screen, indicating a very deep sleep. Your heart rate and blood pressure fall, your breathing is slow and regular, and you will need a ringing phone, shouting or shaking to bring you back to the waking world, which would find you groggy and disorientated and probably not very happy (which is also how you would feel if woken during stage four).
This is followed by the last stage of non-REM sleep, which is even deeper. Your muscles are now totally relaxed and you are difficult to wake up – an onlooker might be tempted to use the phrase ‘dead to the world’.
It is during these deep stages that our body carries out its repair work, fights any illness or damage and, in men, releases the growth hormone.
This is the sleep that truly refreshes us. As the night wears on, the deep stages of sleep become shorter and the REM stages lengthen.
These four non-REM stages described above take you approximately one hour into your first sleep cycle. You will then re-emerge towards consciousness and experience a brief awakening that you won’t remember; this is often when you turn over or grab back some of the sheets.
Dr Paul Caldwell in his book Sleep Really Well suggests that this may be due to an evolutionary need to check one’s environment for danger, as in deep sleep we are very vulnerable.
After- this you start REM sleep, where high-frequency waves begin to appear on the EEG screen. Your brain has now started to create some alpha and beta waves, which are similar to the ones produced when we are awake.
You are probably dreaming and your eyeballs are moving under their lids, which is what gives REM sleep its name (you can also dream in non-REM sleep, but these dreams tend to be simple and short).
Although dreams seem very real and physically active, your body won’t act out your dreams as your muscles are paralyzed in this stage and you remain motionless (some scientists believe that this is the body way of preventing you from harming yourself.
Sleepwalking is likely to happen in the non-REM part of your sleep, which isn’t accompanied by paralysis.
A full cycle of non-REM and REM sleep takes about 90 minutes: about 60 minutes in the various forms of non-REM sleep, and between 10 minutes and up to 30 minutes of REM, with the REM sleep periods lengthening gradually throughout the night.
In total, 20 per cent of an average night will be spent dreaming. (Age also affects the proportion of sleep types you have, with less REM as you get older.) Once you have completed a full cycle, you return to the first, non-REM, stage and repeat it.
The number of cycles you perform depends on how long you sleep, but most people wake up in the final cycle of REM sleep, which is why we often remember our dreams. As you are naturally closer to the waking state at this time, you will feel more refreshed emerging from this sleep stage.
Sleep watches have been developed, which monitor your body and look for these ‘almost awake’ moments, triggering your morning alarm clock and ensuring you wake during these parts of your cycle.
Of course, getting the right amount of sleep would make this a natural occurrence, but for those who need to be up at certain times, setting a window of about 20 minutes for the watch to seek out the optimum, least distressing time to sound the alarm can make the interruption less agonizing.
The body has its own pacing mechanism – the circadian rhythm – that decides when we feel perky or sleepy; we can choose to respect it, or not. Restless sleep and rhythmic jerking of the feet or legs can be a sign of periodic limb movement in sleep (PLMS), a disorder that impairs sleep quality.
There can be a few unexpected additions to this sleep pattern. For instance, despite a conviction that we may have slept soundly throughout the whole night, we usually wake up from the shallower phases of sleep several times – we just don’t remember doing it. Some research has shown that muscles in the body do not need sleep, just periods of rest.
All research does agree that sleep is essential for the brain. Electroencephalogram (EEG) results show that the parts of the brain that deal with emotional issues, for example, are very active. This has fostered the new belief that we need sleep to process our daily feelings and consolidate our memories.
Some scientists say we only dream the memories and situations that are meaningful to us, while others consider dreaming to be a way of shedding information that is surplus to requirements or trivial. Either way, it seems to be an essential part of our mental wellbeing.