What is Sleep?

Ahh, that lovely feeling of floating downstream as you slowly drift off to sleep! Arms and legs get heavy and the mind wanders freely through grassy meadows and alongside peaceful streams. If only it were always like that! Or even sometimes. For those suffering from sleep problems the mysteries of sleep can be enough to keep you awake at night but puzzling over them doesn't always help bring the sleep we crave. So what is sleep and what can we do when we can't sleep?

Sleep is certainly not doing nothing! It seems to have some really important functions in enabling us to recover from the stresses and strains of the day. Our brain works hard during sleep breaking down chemicals and toxins and getting ready for the day ahead. It's not surprising we struggle so much when our sleep is disturbed.

The role of chemical messengers

Chemical messengers in the brain – neurotransmitters - have a really important role in helping us go to sleep, and in waking us up again. There are two neurotransmitters that keep us awake – serotonin and norepinephrine. When we sleep we need these transmitters to be turned off and there are various cues that prompt this. During the day another chemical – adenosine builds up in our blood and makes us feel drowsy and is broken down as we sleep. And there's the hormone, melatonin which also helps to make us drowsy in the evening and can help us to stay asleep through the night.

To some extent we are programmed to wake up in the day, get our work done and then wind down and prepare for sleep at the end of the day. Light has a big impact on sleep and dictates our circadian rhythm – this is basically our internal body clock which responds to our environment and makes us sleepy. Our circadian rhythm is what gets confused when we are jet-lagged, and why people working night shifts can really suffer as a result of their irregular sleeping habits. It's also why there is a very high rate of sleep disorders in those who are completely blind; without the light cues, it's much harder for our bodies to recognise when to send out those neurotransmitters. To read more this is a great website with loads of information: http://healthysleep.med.harvard.edu/healthy/science/what/sleep-patterns-rem-nrem

The Stages of Sleeping

There are four main stages of sleep plus the infamous R.E.M. sleep phase. Let's have a quick look at them:

Stage 1: This is the “just drifting off stage”. During Stage 1 we drift in and out of sleep and are easily roused. Our muscles begin to relax giving that heavy feeling. It's during this stage that people often have unexpected muscle jerks and may feel like they are falling. During Stage 1 those who have Periodic Limb Movements of Sleep (PMLS) experience the majority of their symptoms, making it difficult for them to fall asleep. For more information about PMLS click here https://www.webmd.com/sleep-disorders/periodic-limb-movement-disorder#1

Stage 2: It usually takes between 5 and 15 minutes to move from Stage 1 to Stage 2. During Stage 2 sleep, eye movements stop and brain waves slow down. There are occasional bursts of rapid brain waves called sleep spindles, but mostly everything is quiet during Stage 2. Now we are heading into deep sleep.

Stage 3: This is the first stage of deep sleep, in which our brain waves become very slow. So slow they have their own name – delta waves. During Stage 3 sleep, less than 50% of brain activity is made up of delta waves.

Stage 4: The second stage of deep sleep. During Stage 4 sleep more than 50% of brain activity is made up of delta waves. In the past, it was thought that dreaming only occurs during REM sleep but it looks like we do also dream during deep sleep. Newborn babies spend a lot more of their sleep time in deep sleep than adults and the amount of deep sleep a person experiences decreases as they age. It's really hard to wake up when you're in deep sleep. Having been woken by a baby during this phase of sleep it feels like you're climbing up out of a deep well, groping towards wakefulness! Some people who sleepwalk, do so during deep sleep which is why they can be so disoriented and confused if they are woken up.

Rapid Eye Movement Sleep: R.E.M.: Most adults have a sleep cycle that takes about 90 minutes and alternates between non-R.E.M and R.E.M sleep. R.E.M sleep is quite different from the other stages of sleep in that the brain is active and this is when we are most likely to dream. Through the night we cycle through sleep stages, but deep sleep is most likely to happen early on with more R.E.M sleep occurring as we near the morning. This is why dreams we have later in the night are usually the ones we remember. Babies tend to have sleep cycles of about 45 minutes which is one reason they tend to wake through the night so frequently until they learn to link sleep cycles.

During R.E.M sleep our breathing becomes more rapid and shallow, there's a lot of eye movement (hence the name!) and our limb muscles may become temporarily paralyzed. One interesting thing is that we are much less able to regulate our body temperature during R.E.M sleep which is one of the reasons it's important that our bedrooms are the right temperature for sleeping. We are not the only to have a R.E.M sleep stage – most mammals and birds do too (those twitching legs really do suggest the dog is dreaming about running!).

What happens when it goes wrong

There are many different causes for disturbed sleep but there have been some fascinating studies done into what happens when our sleep is disrupted. During healthy sleep, we drop down through stages 1,2,3 and 4 and then back up into R.E.M. Ideally we then drop down again into deep sleep once or twice more during the night. Through the night, the amount of deep sleep declines and the amount of R.E.M sleep increases.

However, if our sleep is disturbed we are likely to drop straight into R.E.M sleep; this feels familiar to anyone who has had problems sleeping – suddenly you drift off into wild and bizarre dreams and wake feeling like you need several more hours of rest after a busy night of dreaming. This is also why it's not really possible to catch up on sleep because it's not the deep, restful sleep that we fall into. We also spend a lot longer in R.E.M sleep if our sleep is disturbed rather than cycling through into deep sleep.

How a weighted blanket helps

There is now a lot of research showing that weighted blankets are one of the most effective non-medicinal sleep aids. Looking at the stages of sleep it's easy to see why. In Stage 1 our muscles become heavy but we can be disturbed by muscle movements and the feeling of falling. A weighted blanket can really help with this. The pressure from the blanket reduces muscle movements making it much easier to drift off to sleep. There's also lots of evidence that it helps those with anxiety, stilling both the body and the racing mind. A weighted blanket supports the body's natural sleep processes, promoting stillness and relaxation and helping waves of deep, refreshing sleep wash over us. Bliss!

If you want to read more about the science of sleep, here's another useful website to help you: https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep#2