We’ve all experienced a sleepless night, and how that affects our mood in the morning, but our mood isn’t the only thing that is affected when we deprive ourselves of the necessary amount of quality sleep.
Although we don’t realise it, we actually have sleep cycles, which we go through multiple times through the night. One full sleep cycle normally takes 90-120 minutes and has a variety of different stages that we pass through, these are:
- Non-REM stage 1
- Non-REM stage 2
- Non-REM stage 3
- REM (Rapid Eye Movement)
Non-REM stage 1
This stage normally equates to around 5% of total sleep time, this is the transitional period between being awake and being asleep. This is the stage in which we might not realise we have even been asleep as we are still very aware of what is going on around us. This is also the stage in which we sometimes experience that “falling” sensation.
Non-REM stage 2
This stage normally equates to about 45-50% of total sleep time, as we will pass through this stage multiple times throughout the full sleep period. In this stage our muscles start to relax more, and we become less aware of what is around us.
Non-REM stage 3
This stage normally equates to about 15-20% of total sleep time, with more time spent here within the first and cycle sleep cycles compared to those coming after. In this stage, we are totally dead to the world, and if we are woken from this stage, that is when we experience that really groggy feeling.
This stage normally equates to about 20-25% of total sleep time, with more time spent in here in the latter sleep cycles. This stage gets it’s name from the rapid (and often random) side to side movements of the eyes under the eyelids and – although it hasn’t been proved – is believed to be caused by the visual images of dreams. Although the brain is more active in this stage, the body becomes totally paralysed, it is thought that this is to prevent ourselves from self-harm during vivid dreams*. In REM sleep we will often do something called a “micro-awakening” in which we wake from sleep for a maximum of a few seconds before going back to sleep, normally we don’t remember these but if we are fully awoken at this point, it can sometimes take up to 2 hours to get back to sleep!
IMPORTANCE OF THESE STAGES:
Non-REM stage 1
It is believed that we have evolved to use this stage as a precaution to any dangers around us before falling into a deeper and more vulnerable sleep.
Non-REM stage 2
This is when sleep consolidation (when short term memories are turned into long term memories) begins, this is vitally important for learning new skills.
Non-REM stage 3
The highest amount of sleep consolidation occurs within this stage, with a main focus on “declarative memory” – memories that can be recalled (or declared), i.e. Dates, names, numbers, etc.
Human Growth Hormone is released in the first phase of stage 3 sleep – this is important for muscle and repair and growth; fat and sugar metabolism, and the regulation of body composition.
REM sleep has proven to be imperative when trying to learn complex tasks, and it has been noted that we will spend more time in REM sleep when we have been in unusual situations, requiring us to learn a lot of new tasks. REM sleep is also crucial for muscle repair and growth, as this is the time in which the brain is entirely “detached” from the body.
WHAT HAPPENS IF WE DON’T GET THE RIGHT ABOUT OF SLEEP?
There are many adverse effects of having an insufficient amount of sleep, a few of these include:
- Excessive day-time sleepiness
- Lack of energy/lethargy
- Decreased power output (in strength training)
- Increased weight gain (sleep helps the production of leptin [a fat burning hormone] and decreases the production of ghrelin [the hunger-stimulating hormone])
- Increased risk of diabetes (deep sleep helps regulate the use of glucose in the body)
- Decreased fertility (due to the reduced secretion of reproductive hormones)
These are just a few, but in very serious cases of sleep deprivation, people have actually DIED!
GETTING THE RIGHT AMOUNT OF SLEEP
As with anything, no two people require exactly the same amount of sleep, the average has shown to be 6-8 hours for an adult though it has been shown that 5-10% of people NEED more sleep – 8-10 hours – whereas there is around 5% of people that only need 6 hours at a maximum.
The only way to truly figure out what amount we need, is to experiment. Typically a full sleep cycle is between 90-120 minutes, and it is best to wake up when we are the closest to being awake (Non-REM stage 1 or REM) so that we don’t experience that groggy feeling.
* this theory comes from a study by Michel Jouvet, who severed the nerves that paralyse the muscles in cats during sleep, causing the cats to jump around and stalk invisible prey during REM sleep.