What is sleep and what are the different stages of sleep?
When you ask the question ‘What is sleep?‘ it seem such a silly thing to ask! I mean, everyone sleeps, we all do it, so we should all know what it is.
The problem is that many of us don’t sleep very well, in fact quite a few of us suffer from insomnia, which is long term and chronic sleep deprivation. You might be surprised to learn that sleeping disorders are very commonplace with a lack of sleep being described as a public health problem.
Just to add a few numbers to the topic of sleeplessness, a sleep study in 2009 found that between 30% to 45% of people over the age of 18 had unintentionally fallen asleep during the day, at least once in the previous month.
Sleep, which is very illusive to some people, has been described as a change in our consciousness, but this is not a passive state at all, because our brains are very active when we are asleep.
We don’t just fall asleep and wake up with nothing in between. Some heavy sleepers might think that this happens, because they can’t remember anything after falling asleep. The truth is far different however, because there are in reality, five stages of sleep and we cycle from stage one through to five and then back to stage one as we continue sleeping.
When you have trouble sleeping, it helps to understand these sleep cycles, so you can work out where your problem lies in the sleep cycle. For example, we spend around 50% of our sleep period in stage two, around 20% in stage five and the remaining 30% is split between stages, one, three and four. Babies on the other hand, spend around 50% of their sleep periods in stage 5.
Stages one through four are considered to be non-REM sleep, whilst stage five is REM sleep.
The five stages of the normal sleep cycle
Stage one: This is a light sleep period when we can be easily awakened and we drift in and out of sleep. The activity of our muscles lows and are eyes still move, but slowly.
If you wake frequently during stage one you quite often remember fragmented visual images and you can also have a feeling of falling.
Stage two: At this point, the movement of our eyes stops and our brain waves also start to slow down, as our sleep deepens.
Stage three: Our sleep cycle has deepened further and our brain waves have continued to slow, starting to show delta waves.
Stage four: At this point we are deeply asleep and our brain waves are almost exclusively delta waves. There is no eye movement or muscle activity and it is difficult to wake someone is stage three or four of the sleep cycle.
If awakened, people at this point in the sleep cycle feel very groggy and it takes a while for them to wake fully. This is the int in your sleep cycle where sleep walking can occur.
Stage five or REM sleep: REM sleep usually occurs around 70 minutes after stage one and only lasts for about 10 minutes at first. The entire sleep cycle takes approximately 90 minutes, before it starts again at stage one.
In stage five, our heart rate, blood pressure rise and respiration rate all rise, our eyes jerk rapidly (REM or rapid eye movement) and we cannot move our muscles. If you wake during REM sleep, this is where you quite often remember dreams.
As you continue sleeping and each complete cycle repeats itself, the time spent in REM sleep increases and the time spent in stages three and four (deep sleep) decreases. By morning, you are spending most of your sleep period in stages one and two, as well as in REM sleep.
For us to feel well rested, we need to experience the complete five stages of the sleep cycle and a good night’s sleep is said to consist of five or six complete cycles. If you have trouble sleeping, your sleeping period will consist of less than this beneficial number of completed sleep cycles.
The sleep cycle and our circadian rhythm
Our circadian rhythms represent how our physical and mental activity changes during the day and this is affected by daylight.
Our brain’s circadian clock, which is located in the hypothalamus inside our brain, syncs itself to the amount of daylight and regulates our brain activity, our hormone levels, our body’s temperature, our sleeping and eating patterns, and many other biological functions.
One of these hormones that your circadian clock regulates is melatonin, which makes us feel sleepy. As the amount of daylight reduces, your body produces more of this hormone and you start to feel drowsy and ready for bed.
Circadian rhythm disorders, which disrupt our sleeping and waking cycles, occur when our lifestyle doesn’t sync with our body clock. These type of sleeping problems are commonly seen in shift workers and travelers, as well as in people who suffer from seasonal affective disorder.
When your body clock is out of sync with the 24 hour clock, you can have trouble sleeping resulting in fatigue, lack of focus and concentration and a general feeling of being tired and grumpy all of the time.
Causes of sleeplessness
There are a whole host of causes of sleeplessness, with the most common cause being a disrupted sleep pattern, due to shift work, jet lag or being a parent!
People who perform shift work have problems adjusting their body clock to an abnormal sleeping pattern, particularly if they work night shift and need to sleep during the day. Jet lag is another cause of trouble sleeping, as your body clock needs to readjust itself to the local time zone and this can take days or even weeks for some people.
Then we have parenthood, where mums and dads are continually woken at night to attend to their newborns, toddlers and young children. Not forgetting all of those people whose sleep is disrupted by noisy neighbors, dogs barking, busy traffic, airplanes flying over, loud TVs and a host of other extraneous noises that you cannot control.
Other causes of sleeplessness include insomnia, restless leg syndrome, sleep apnea, narcolepsy and periodic limb movement disorder.
Solutions for sleeplessness
Obviously, the solution depends on the cause, but for sleeplessness caused by shift work and jet lag or by being woken by your children or outside noises, you will most probably find that a sleep sound machine will help.
Sound machines work because they mask or block out external noises like traffic, noisy neighbors or your partner snoring and help you to sleep more soundly during the day or night. They also help you to relax so it is easier to fall asleep, as some people not only have problems sleeping, but actually falling asleep is also a problem for them.
Seasonal affective disorder, where the days are shorter, can be helped by a sleep sound machine, but they can also be helped by light therapy as well. This type of natural treatment works to resync your body clock and is also very effective for shift workers and suffers of jet lag.