We all know that ideally we should be sleeping for 8 hours each night - we’ve been told that for decades. For some of us that isn’t a problem. For others it rarely ever happens, and that is for a variety of reasons. It could be a genuine sleep problem or disorder, alcohol/drug use, stress or anxiety, we don’t have the time or that some of us are simply not good sleepers.
But what exactly is sleep? There are different types of stages of sleep, as you might have heard. There are 2 main types of sleep; REM (rapid eye movement) and non-REM (NREM) sleep, and they each have their own distinct neurological, physiological and psychological features. Our sleep stages move in cycles with REM sleep being fairly simple and NREM sleep having distinct cycles that we move through as our sleep progresses. We move through the entire cycle multiple times per night – as if stuck in a roundabout - with the REM stage lasting for progressively longer periods and the NREM cycles shortening.
Non-REM sleep is broadly characterized by very slow but very high amplitude brain wave oscillations with REM sleep characterized by very fast but fairly low brain wave oscillations. What does this mean?
This means that REM sleep displays brain wave activity that is fairly similar to how our brain behaves when we are awake, though our body is essentially completely paralyzed during this stage to stop us from acting out our dreams. REM sleep accounts for roughly 25% of our sleep and, interestingly, infants spend up to 80% of the night in REM sleep and it has been found that it is necessary for humans to spend time in REM sleep for us to be able to learn and memorise complex tasks and in memory consolidation.
During NREM sleep the body is not paralyzed and we will usually make a fairly substantial movement during this stage of sleep, usually every 30 minutes. Early sleep researcher William Dement noted that NREM sleep is essentially an idling brain in a moving body and this contrasts quite strikingly to REM sleep where the brain is very active and the body is idling. There are 3 stages of NREM sleep each with their own distinct features.
Stage 1 of NREM sleep is often called somnolence and is very short and easily disrupted, lasting only 10 minutes. This stage is the quick transition from being awake into a deeper sleep. Most of us spend this part of sleep on the couch before transferring to bed!
Stage 2 of NREM sleep is where conscious awareness of the outside world completely ceases. This stage of sleep has been shown to be an important part of information processing and memory consolidation and we spend roughly 50% of our sleep cycle at this stage.
Stage 3 sleep is our deepest stage of sleep and at this point of the cycle we are very unlikely to awaken for any reason. If we are awoken from this stage, we are likely to feel very disorientated and it will often take up to 30 minutes for us to feel as though we have completely woken up. This stage lasts for longer periods during the early stages of the evening and shortens as our sleep cycle continues. Breathing rate, heart rate, temperature and blood pressure are also at their lowest during this stage with memory consolidation also being an important feature. This is also the stage where parasomnias such as night terrors, sleep walking and sleep talking occur.
But how much sleep do we need? This is a difficult question to answer because the volume of sleep that we need is going to be influenced by a variety of factors. Certainly we now know that genes will play a role in determining how much sleep we need to be able to function without any cognitive impairment. For example, around 10% of the population need more than 8 hours of sleep each night to be able to function at a normal level, whilst about 5% of the population are able to sleep less than 6 hours per night unaffected. The volume of sleep the we need will be completely individualised, which is why it is critical for us to be in tune with our body with regards to how much sleep we feel that we truly need.
And if we don’t get enough sleep? Sleep deprivation certainly leads to mental, emotional and physical problems, some of which we might not even be aware of. Day-to-day activities and high level cognitive functioning will be dramatically impaired when we are deprived of our personal sleep requirements. Critically, our judgement can be impaired on a level similar to that seen during alcohol intoxication.
With all of that in mind, how can we sleep better? There are several strategies that you can try and these include sticking to a sleep schedule as closely as possible; avoid going to sleep on a full stomach or having recently consumed caffeine, nicotine or alcohol; create a ritual that you follow each night before bed; be comfortable and create a dark and quiet space; limit day time naps; do the best that you can to manage your stress and, most importantly, add regular exercise to your routine!
Yours in health!