The Science of Sleep


Why we spend so much time at rest, and the potentially deadly consequences of missing it

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Image by Alexander Possingham

By Robyn Garner

The importance of sleep is often overshadowed in today’s productivity-centred society; the benefits of a steady circadian rhythm drowned out by a desperation to achieve goals as fast as possible. When examined in isolation, sleep can appear bizarre, and until recent years the reason behind it was almost entirely a mystery. As research into what causes the need for a third of our lives to be spent in a comatose state developed, it became clear that there is not a single overarching reason for this but a myriad of interlinking ones which have the potential to vastly affect our day to day lives.

A central part of the science behind sleep is the innate circadian rhythm that each human possesses. Instinctively, it may seem that our sleep schedules are governed by the setting and rising of the sun. From a societal perspective, this is broadly true; we have adjusted to conduct our lives in the optimum living conditions, however light is not necessary to enforce a roughly 24 hour schedule. In 1938, researchers Nathaniel Kleitman and Bruce Richardson subjected themselves to life in complete darkness for six weeks, dedicated to determining if sleep was in fact governed by internal processes or outside suggestive factors such as sunlight and temperature. The outcome was that they remained in roughly 24 hour cycles, with both men sleeping in slightly longer patterns. The uncovered circadian rhythm has been found not only to dictate sleep, but also our temperature, digestion and hormonal responses.

A natural circadian rhythm has now been measured to be on average about 24 hours and 15 minutes. The suprachiasmatic nucleus, located at the intersection of the optic nerves from the eyeballs, allows this slight inaccuracy to be reset each day through the processing of sunlight hitting the optic nerves. These rhythms do not always adhere to the exact structure of the day that is expected from many jobs and schools; undoubtedly relevant to approximately 30 percent of the student populace who are night owls while the dreaded compulsory 9am lurks. All humans have slightly varying circadian rhythms, and the widespread concept of night owls and early birds is a very real, involuntary phenomenon founded in genetics. It would be difficult to comfortably design a consistent timetabled social structure to cater to all simultaneously.

Despite the variance in schedules which exists automatically, circadian rhythms can be thrown off-kilter in a way that affects health. Shift workers are especially at risk of suffering adverse effects due to the erratic nature of their waking hours. A lack of consistency that interrupts this natural cycle can lead to a depressive mood, memory impairment, disruption to menstrual cycles and a higher chance of various types of cancer.

Aside from shift work, a culture centred on heightening valued forms of productivity at all costs is not necessarily conducive to good sleep hygiene. While it may seem in the moment to be advisable to skip out on sleep in the name of studying for an exam or scheduling in extra hours to scrape in more cash, in reality the lack of sleep is more likely to inhibit your productivity and result in a lacking performance. Concentration is an inevitable victim of poor sleep, a lack of which can result in anything from a dropped grade to a deadly car crash. Microsleeps, a momentary involuntary closing of the eyes, become common in people with consistently poor sleep. All awareness of reality is sacrificed in these moments, with deadly consequences when experienced whilst speeding along a motorway at 70mph. A study in Australia found that a person who has not slept for 19 hours is at the same level of cognitive impairment as a person who is legally drunk.

Sleep problems can persist as insomnia as well, a disorder that is expected to affect 1 in 10 people. While many people forcibly deprive themselves of sleep, be it for reasons of work or pleasure, insomniacs simply lack the ability to fall asleep for adequate amounts of time at all. The condition can manifest as both ‘sleep onset insomnia’ – difficulty falling asleep, and ‘sleep maintenance insomnia’ – difficulty staying asleep. Common triggers can be emotional distress or disorders such as anxiety or depression, as well as disorders such as ADHD. Insomniacs can have a false impression of their ability to function on little sleep for a variety of reasons. One of these is that the background level of tiredness they experience has become their normal baseline and is consequently no longer notable.

A lack of sleep can also go unnoticed due to sleeping for incomplete REM (rapid eye movement) cycles – a complete cycle in which the brain completes all four stages of sleep. REM sleep is the final stage of this cycle, during which dreams occur. At this stage a person’s eyes will move rapidly, and their breathing will become irregular as their heart rate speeds up and brain activity increases. Each full sleep cycle takes between 90 and 120 minutes to complete, meaning the average adult with good sleep hygiene will experience approximately four per night. At this stage of sleep, multiple important processes occur, including memory consolidation, emotional processing and the activation of the central nervous system in order to prepare the body to wake.

In a world where sleep is not prioritised, it can become the first thing to slip through the cracks and start to cause a cascade of problems of its own. The more the science behind the mystery of sleep is uncovered, the more its necessity becomes clear. Perhaps one day the big answer behind why we do spend so much of our lives at rest in a world of our own will become clear.