Sleep. We all need it. But sometimes it feels like we’re wasting those precious hours when there’s so many other things we could be doing! However, we all know how much better we feel after a good night’s sleep, given the health benefits that regular, unbroken sleep provides us – as elusive as that may be for some!
So what happens when we are deprived of our much needed sleep? Sleep deprivation (SD), whether intentional or inadvertent, takes those health benefits away, and without a doubt, you’ll miss them when they’re gone.
There are various phases of sleep, forming multiple cycles. During around 75% of your sleep you enter non-rapid eye movement (NREM) sleep, which is defined by three distinct phases. During N1, you fluctuate between being awake and asleep. Not a whole lot happens to you on a physiological level – although some of you may experience hypnic jerks, sudden muscle spasms that may shake you awake.
When N2 occurs, the ‘real’ sleep begins and you become unaware of your surroundings. Your core body temperature drops but your breathing and heart rate remain steady. However it’s not until you reach N3 that you fall into a “deep sleep”. Here, your blood pressure drops and remains low – which boosts cardiovascular health – your muscles relax and your breathing slows, and the blood supply to your muscles increases. Tissue growth and repairs are prioritised, and hormones vital to your proper functioning are released, including those that regulate feelings of hunger. In addition, your hippocampus, which deals with memory consolidation – among other things – shows an abundance of electrical activity as you sleep. Recent studies have suggested that short-term memories acquired throughout the day appear to be progressively transferred to the cortex for long-term “storage” at night.
Interestingly, something that depletes immediately after just one less night of sleep is those all-important cognitive reasoning and retention functions. From grammatical reasoning and spatial planning to memory recall activities, our abilities begin to drop off to varying degrees.
It also appears that there’s far less activity going on in the frontal and parietal lobes, which deal with problem-solving and decision making. In 2017, a landmark review on this subject noted that your visual cortical regions also show an increasingly reduced signal over time during visual working memory tasks. Reaction times and learning also fall by the wayside.
The brain’s reward system is also shown to be sensitive to SD, which can cause changes in how a person seeks out risks, sensations, and takes impulsive actions. Essentially, the more SD you experience, the more of a clumsy fool you’re likely to become.
The 2017 review also notes that based on the “limited evidence to date”, SD begins to trigger reductions in the brain’s “intrinsic connectivity profile”, essentially meaning that the wiring linking up parts of your brain become less effective. A separate study highlights that brain cells themselves are less able to communicate with each other too. This is also one of the reasons why you become physically uncoordinated as SD worsens.
This, along with reduced blood flow to said regions, is thought to be connected to not just cognitive, but “emotional impairments”. SD makes the person less able to display positive emotions, and less able to recognize them in other people. Negative emotional experiences become increasingly harder to deal with as the days go on, and some people may experience a state of delirium and even hallucinations.
Whether or not they’re true, full-blown hallucinations or merely ephemeral flickers in their peripheral vision are up for debate, but either way, the brain will be less able to process sensory information as times ticks by.
Physical health is inextricably linked with mental health, too. Those that sleep well are far less likely to experience depression, anxiety, and other related mental health problems. In the absence of it, such afflictions may appear or worsen if already present.
SD means that those feeling of famishment-controlling hormones aren’t being released in quite the same way either, and your body stops metabolizing glucose efficiently. As noted by Slate, you’re consequently going to desire more carbohydrates than necessary, which may indirectly lead to weight gain in the long run.
With just one single sleepless day, cortisol and thyroid-stimulating hormone levels rise, triggering a higher blood pressure. In the long term, poorer cardiovascular health probably awaits you.
Lest we forget the health of your immune system. A good night’s sleep allows your body to promote the production of cytokines, a family of proteins vital for communication between cells. Similarly, solid snore-sessions allow you to maintain normal levels of immune system cells and associated antibodies.
Over time, through SD, it’s likely your ability to fend off infections will begin to falter as its immune responses are suppressed.
Experiments on mice shows evidence that suggests sleep may “flush” toxins out of the brain, whereby the space between their brain cells increases during the unconscious night by up to 60%. As this happens, cerebrospinal fluid fills the valleys, clearing out toxic byproducts that are associated with neurological impairments as well as far more serious neuro-degenerative disorders. In the long term, then, SD – or chronic sleep loss – could potentially increase a person’s risk of gaining said disorders later in life.
These experiments are difficult to maintain in the long run, and it’s important to note that people respond differently to sleep loss. Is the end result always the same though? Would a near-perpetual SD experience always end in death?
It is possible, but there’s not enough data to definitely say one way or the other. The detrimental health effects alone would be the major contributing factor to your demise. If you were to try and fight it, ultimately your brain would forcefully begin to shut down.
The New York Times published an article whereby in a set of SD experiments on rats, those totally deprived of sleep died in 2.5 weeks; those deprived of just REM sleep took twice as long to perish. An important point to note though, is that it’s not clear what the cause of death specifically was, just as it’s still not entirely clear why, in many aspects, sleep is so necessary for our continued survival.
In today’s modern life, from temporary disruption to insomnia, much of civilization is sleep deprived – and we’re sleepwalking into a health-based nightmare as a result.