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.
