Sleep Tight

Human beings spend, on average, approximately one third of their lives asleep; eight hours a night, every night, for the entire seventy-odd year duration of our lives. We have created inventions and devised entire living spaces dedicated to our pursuit of this activity, which makes it all the more strange how relatively little we understand about it.

The actual mechanisms surrounding sleep are actually quite well documented; ‘everyone knows’ that there are two types of sleep, REM (rapid eye movement) sleep, characterised by one’s eyes moving around rapidly beneath closed lids whilst the rest of one’s muscles remain paralysed, and non-REM (or NREM) sleep. Less people know that NREM sleep is also typically subdivided into three separate types of its own; N1, in which the body is semi-awake and able of moving around, N2, in which one’s brain activity begins to change and it becomes harder to wake up the subject concerned, and N3, in which the body becomes even less responsive. In most people, sleep follows a fixed cycle of N1, then N2, then N3, N2 again and finally a short period of REM sleep before either awakening or the cycle starting again.

Of all these stages, it is REM sleep that provides the most interesting question. Contrary to popular belief, REM sleep is not the only period in which dreams occur (experiments in which sleepers are interrupted during different stages of their sleep cycle reveal that dreams can occur at pretty much any time), but dreams occurring during REM sleep are more common and the most memorable afterwards. It is also during this period in which a subject’s brain activity, at least in humans, most closely resembles that when the subject is awake, but a subject in REM sleep is also hardest to wake up and the least responsive to outside stimulus. It is for this reason that REM sleep is also someone known as ‘paradoxical sleep’.

However, the main reason REM sleep is so interesting is because it is thought to be the only sort of sleep that ‘matters’. To explain; some people nowadays are, apparently, terribly worried by how much time they spend asleep that could be more productively spent watching cat videos on YouTube, so have endeavoured to find alternative sleep patterns that minimise the amount of time they need to spend dead to the world. Most of these involve taking short naps at regular intervals throughout the day, adding up to about two hours sleep time total. An example is the ‘ultraman’ sleep schedule, which involves sleeping for 20 minutes at a time every four hours. When people are first adapting to this technique, it absolutely ruins them; their body is barely getting past the N1 stage before its preset cycle is broken, and they spend their days in a perpetual fuzz of sleep-deprived madness. However, after a week or so, their body learns to adapt to the change, and they find that their ‘power naps’ are perfectly sufficient to survive their sleep needs. When these successful adapters are monitored during one of these naps, it turns out that all of their 20 minute snooze is REM sleep, rather than the 20-25% normally expected. That they are able to function on this two hours of REM just as well as others are on their eight hours of ‘normal’ sleep, which comes out to around 2 hours REM, 6 hours NREM, suggests that it is the 2 hours of REM that causes us to feel rested, and as such is the only ‘important’ aspect of sleep.

This theory would probably be more understood and widely respected were it understood precisely what sleep is for. Whilst sleep deprivation is known to increase the risk of obesity, diabetes and heart disease and to adversely affect the brain, skeletal muscles and immune system, indicating its importance, nobody is quite sure precisely how or why any of it happens. Stanford researcher William Dement, who has spent over 50 years studying sleep and is the man who discovered the different stages of sleep, once said that “As far as I know, the only reason we need to sleep that is really, really solid is because we get sleepy.” Some theories suggest that sleep’s restorative properties stem from the way different chemicals and hormones are secreted during different sleep stages due to differential brain activity, but these arguments generally don’t explain the apparent importance of REM sleep despite it being so neurologically similar to wakefulness. Some suggest that sleep is an energy saving tactic, highlighting the effect that it has on the metabolism of a sleeping subject. However, whilst the body’s resting metabolic rate does decrease whilst sleeping, it only does so by between 5 and 10 percent, which is not evolutionarily sufficient justification on its own for spending eight hours a day incredibly vulnerable to attack. Not only that, but animals who hibernate (a fundamentally different process than sleeping), frequently wake up and go to sleep almost immediately, indicating that sleep fulfils an entirely different function (or set of functions) not satisfied by hibernation alone. Others highlight evidence supporting the idea that REM sleep is crucial to brain development in infants (most of a baby’s sleep time is spent in a REM state), but this doesn’t adequately explain why adults need lots of REM too. Yet another set of adherents point out the connection between sleep and memory, which may also be linked to why our brain reacts so badly to sleep deprivation, but offer no explicit link between the two or the way sleep affects our body physically. The true answer, if ever it is found, will probably lie somewhere in between all of these theories.

The key conclusion that can be taken from this post is, therefore, that sleep is weird. And that’s before we’ve even touched on the weirdest part of sleep: dreams, which I wouldn’t touch here with a ten foot pole. Some things just plain don’t want to be explained, and any field in which Inception isn’t a wholly ridiculous concept is most certainly one of them.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s