Like all species that are known to us, humans spend a portion of their lives asleep. But how many of us wonder why we repeatedly enter this state of sleeping? Despite what we used to believe for so long, our brains are not completely passive when we sleep. In fact, they have some functions they perform especially during this time, that scientists are still exploring and documenting.
How Does Sleep Work?
Sleep is not a homogenous process – it’s mainly divided into two types: REM (rapid eye movement) and NREM (non-rapid eye movement) sleep. The sleeping mechanism is made up of cycles that last for about 90 minutes; each one constituted of a couple of stages that display different brain activities.
During the first stage, we drift in and out of consciousness. The second stage is called the beginning of sleep, while stage three and four are referred to as ‘slow-wave’ sleep. All of these fall under NREM sleep. After that follows the second stage again, and then the brain enters REM sleep. This sequence repeats itself 5-6 times during one night.
How Does Sleep Deprivation Affect the Brain?
In the past, the biggest indicator that used to tell our brain when it was time to go to bed, was light. Although we can prolong that today because we have electricity, adults still need to get a minimum of seven hours, and adolescents nine hours of sleep per night. We can avoid this for so long before we start to notice changes in our behavior – clumsiness, extreme emotional reaction, difficulty focusing, fatigue, and forgetfulness. All of these and more are the consequences of sleep deprivation, something that more than 40% of the adults in the US suffer from. Even napping at work was found to increase overall health and productivity. When the body is sleep deprived, the brain naturally starts to act out.
Sleep deprivation is no joke. Some countries are so bad at catching some z’s that it’s considered a nation-wide health problem. The reason for this is because if you don’t get enough sleep during the night, then your brain underperforms during the entire day. We just cannot complete our tasks as well when we haven’t had a proper shut-eye. The fatigue can even result in microsleeps – short involuntary episodes of sleep – that can be fatal if the affected individual is working a high-risk job, driving a car or watching a child.
Sleep deprivation also entails numerous other health risks — cancer grows twice as fast in a sleep-deprived individual. Individuals that are chronically sleep deprived are predisposed to suffering from mental illnesses, such as depression and anxiety disorder.
Perhaps the most important activity carried out by the brain is memory processing. Our brains are operating all night to arrange and catalog memories that have accumulated in our short-term storage during the day, cementing all the relevant things and discarding the irrelevant ones. Naturally, when a student hasn’t had any sleep before cramming for an exam, he or she is less likely to recall the information he learned. This is because their brain didn’t have enough time to process this information, so technically, it was only stored in the short-term memory.
The Brain’s Cleaning System
All organs in the human body clean the waste they produce with the help of lymph vessels. The brain doesn’t have any of those, so how does it clean itself?
Researchers at the University of Rochester found that the brain has a unique, dishwasher-like cleaning system.
During sleep, the brain cells shrink so that they can enable a greater flow of the cerebrospinal fluid. This fluid washes away all the toxins, including a peptide, called amyloid beta – closely associated with Alzheimer’s disease. Amyloid beta is a natural byproduct of normal, every-day functioning of the brain. The brain gets rid of it at night because the cleaning process requires a lot of energy and it’s best to be done when the body is passive.
This not only explains the connection between sleep deprivation and Alzheimer’s disease but also answers the question why our bodies just cannot work properly when we haven’t had a good night’s sleep.
The Loop: Obesity and Sleep Deprivation
Sleep deprivation affects the way we eat. Individuals who don’t get enough shut-eye consume 500 more calories per day. It’s not uncommon to crave unhealthy foods, high in carbs and fat and at these times, the brain isn’t at its highest performance, so it doesn’t really comprehend the long-term consequences of these foods. This kind of behavior can lead to gaining at least one pound per week and increase the chances of obesity.
In turn, obesity itself contributes towards sleep deprivation, because of a disorder found most commonly in overweight people – obstructive sleep apnea. The throat muscles relax during sleep and block the airway – resulting in snoring. One of its consequences is shallow or completely paused breathing during sleep, with episodes of apnea (decreased breathing) which can last up to 40 seconds.
The Lesson: Get Enough Sleep!
While scientists are still learning about what our brain does during sleep, the facts we know so far cannot be clearer. The conclusion we can all draw from this is that sleep is not a waste of time, quite the contrary — it’s an essential third of our lives that enables us to live the other two-thirds properly.
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