Michael Corke was 39 when he lost his ability to sleep.
His insomnia was aggressive, and his sleepless nights dragged on. Confusion quickly began to set in, followed by hallucinations and a loss of balance. Eventually, unable to sleep at all, he was admitted to the University of Chicago hospital where doctors wrongly diagnosed him with clinical depression, brought on by multiple sclerosis (MS) a neurological disease that causes problems with vision, movement, sensation and balance.
They attempted to alleviate Corke’s symptoms by inducing a coma, but that didn’t work, as his brain failed to shut down completely. He died in 1993, a month after he turned 42, bedridden, paralysed and mute.
Corke was found to have fatal familial insomnia (FFI). A rare, incurable and invariably fatal genetic disease that causes patients to lose their ability to sleep – completely. It is autosomal dominant, which means that someone who inherits the gene from just one parent has a 50% chance of succumbing to it over the course of their lifetime.
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The mutated gene expresses itself without warning, usually between the ages of 20 and 61, and causes the accumulation of abnormal prion proteins in the brain, leading to rapid cognitive decline and motor dysfunction. Hallmarks of FFI include worsening insomnia, an inability to balance, excessive sweating, elevated pulse, short-term memory and attention deficits and endocrine dysfunction. Death inevitably follows, usually around the 18-month mark.
FFI is a tragic reminder of the critical importance of sleep in a society where sleepless nights are worn as a badge of honour. But why is sleep so important and what happens in the brain while we slumber?
Why sleep is so important
Scientists have discovered a revolutionary new treatment that makes you live longer. It enhances your memory and makes you more creative. It makes you look more attractive. It keeps you slim and lowers food cravings. It protects you from cancer and dementia. It wards off colds and the flu. It lowers your risk of heart attacks and strokes, not to mention diabetes. You’ll even feel happier, less depressed, and less anxious. Are you interested?”
The passage above is an extract from the book Why We Sleep by neuroscientist and sleep expert, Matthew Walker, PhD. Walker, of course, is describing sleep and more than 17,000 scientific studies support his claims. Some form of sleep is observed in all studied species and humans are the only ones that deliberately deprive themselves of it.
To further illustrate the importance of sleep, Walker describes the annual “global experiment” of daylight savings time, where 1.5 billion people are forced to lose an hour of sleep for one night every year. Data from millions of hospital records show a spike in heart attacks and road traffic accidents, a day after the clocks change in March and a dip when they change back in November.
A clear link exists between inadequate sleep and sub-optimal mental and physical performance; even losing an hour of sleep isn’t as trivial as we’d like to believe.
Insufficient sleep can lead to episodes of microsleep – brief periods during wakefulness when the brain shuts down, causing a temporary loss of consciousness, without us realising it. It also slows down our reaction times and affects our brains just as much as alcohol, making it a leading cause of road traffic, and fatal occupational accidents. Accidents related to sleep deprivation have been estimated to have an annual economic impact in excess of US$40 billion.
While there is still no broadly defined consensus among researchers around why we sleep, there is no dispute that sleep is not a state of complete inactivity, but a complex physiological process that is critical to our survival. Chronic sleep deprivation can impair brain development and lead to hyperactivity and disruptive behaviour in children. It has also been linked with the development of Alzheimer’s disease, immune deficiency, and an increased risk of diabetes, cardiovascular disease, depression, and even obesity.
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Furthermore, recent epidemiological data from the USA suggests the existence of an inverse relationship between the number of hours that people sleep and the proportion of people in the population who are obese.
What happens in the brain while we slumber?
One of the most important functions of the “sleeping” brain is memory consolidation. Neural networks that were active during the encoding of a memory reactivate, strengthening connections between neurons involved in the memory. Memories are also transferred from the hippocampus, which is important for their initial encoding, to the neocortex, where they are stored long-term.
The process also involves synaptic pruning, which helps us forget unimportant things. This, alongside the sleep-induced production and release of growth factors and cytokines, is also thought to aid in cellular repair and regeneration by clearing out old, damaged synapses and allowing for the formation of new ones.
In the 1950s, Eugene Aserinsky and Nathaniel Kleitman discovered that sleep has different stages based on their ocular features. The sleep cycle consists of oscillations between rapid eye movement (REM) sleep and non-REM (NREM) sleep, where the latter can be further subdivided into 4 stages of light and deep sleep.
The different stages of sleep have distinct functional roles that likely change as we age. They also play different roles in memory consolidation. Slow-wave sleep (SWS) or stage 3 NREM sleep, is the deepest stage of sleep and is important for consolidating memories of facts and events, while REM sleep is important for consolidating procedural memories. This means that sleep is also essential for learning and its deprivation inhibits learning by weakening retention, and making us inattentive and unable to solve problems creatively.
Sleep, especially SWS, also activates the brain’s janitorial service. Known as the glymphatic system, this is an important mechanism that helps the brain remove accumulated toxic waste, including beta-amyloid, the protein associated with Alzheimer’s. It works by utilising a network of channels that run alongside the brain’s blood vessels. As brain cells shrink while we sleep, these channels expand, allowing cerebrospinal fluid to flow through taking waste products along with it.
Lack of sleep can also leave us stressed, impair cellular repair and disrupt the hormones, leptin and ghrelin, that control appetite and satiety, leading to increased hunger and subsequent weight gain; it can also disrupt glucose metabolism leading to an increased risk of diabetes. And according to Johns Hopkins sleep expert and neurologist Mark Wu, M.D., Ph.D., even a single night of missed sleep can create a state of prediabetes in an otherwise healthy person.
All of this, of course, is far from a comprehensive list of everything that our brain does while we sleep and question marks continue to remain around why our brain needs to disconnect from the environment for several hours every day. Whatever the explanation might be however, there’s no doubt about the fact that sufficient shut-eye is non-negotiable for good health and a sleepless night really isn’t something that deserves bragging rights.