Why We Sleep: An Underappreciated Mechanism

What Goes Wrong Without Sleep

The best way to understand why we sleep is by observing what happens when people get less of it. The first point to note is that sleep does not work on a credit system; one hour of lost sleep cannot be “paid” back by extra sleep the next day. If you lose one hour of sleep, that hour will forever be lost, damaging your health a little at a time. It will become clear that even the smallest loss of sleep results in massive consequences for our health. This is because humans are the only species that willingly cut their sleep time short. As a result, nature never had to develop defense mechanisms against short sleep.

General Phenomenons

That being said, here is a list of the few dysfunctions attributed to sleep loss:

1. Loss of Concentration: An important function of sleep is harnessing the emotional parts of the brain via the conscious brain. If you have ever been sleep deprived, you know that one moment you can be annoyed and the next you can be laughing yourself to tears. This is because your amygdala, the emotional center of the brain, becomes hyperactive when one reduces sleep. This leads to emotional instability and a reduction in your ability to focus on one task.
2. Imperceptible Loss of Brain Function: At this point, you are probably thinking that you are someone who can run on 6 hours of sleep and be just fine. You’re probably running on 6 hours of sleep as you read this sentence. However, the reason you feel like this is because you are trying to analyze your own physical state. This is the same effect as a drunk person saying, “I’m fine, give me the keys”. Subjectively, you may feel fine but objectively, you are far from that.
   
   Studies have shown that our brains compensate for reduced sleep duration by partaking in a process known as micro-sleeps. This is not what happens when you nod off in the middle of class. Rather, the process of micro-sleeps is nearly impossible for one to self-observe. Essentially, your brain switches “off” and enters the sleep state for a few microseconds at a time. During this time, you cannot remember nor be aware of anything. Your brain puts your life on pause for a few microseconds at a time. As a result, you don’t realize that you are sleeping at all. In fact, someone who sleeps 6 hours per night for 10 days has the same amount of micro-sleeps as someone who hasn’t slept for an entire night.

Nervous System and Hormones

Sadly, the news only gets worse from there:

3. Blood Pressure Increase: A cascade of hormonal changes begin to affect you body after just one hour of lost sleep. First, the body triggers a stress response because of the unnaturally short sleep duration. Your heart rate remains elevated all day, forcing more blood through your vessels, slowly wearing them down with more blood flow. This makes sense, the only reason a wild animal would miss out on sleep is if it is hunting for food or running from danger. This response would provide the energy needed to accomplish the task. Unfortunately, this is not an acute episode for most, it is a lifestyle defect.
   
   Similarly, cortisol, a stress hormone, gets released into the blood. This hormone constricts blood vessels, increasing the pressure each arterial wall has to endure. In addition, growth hormone levels plummet, stopping the vessel repair pathways from activating. Finally, the stress response begins to save energy for immediate action by shutting down the immune system and tumor suppressor genes, leading to increased risk of cancer and illness. A study demonstrated that one night of 4 hours of sleep resulted in a 70% reduction in the number of killer T-Cells (anti-cancer/infection white blood cells) within one’s bloodstream.
4. Metabolic Instability: We have spent a good amount of time discussing insulin and evolutionary eating habits. With the advent of shortened sleep, all of these hormonal systems become unstable. In fact, sleep is the single most important factor for predicting whether your healthy habits will show your desired results. First of all, short sleep leads to chemical changes within cells, making them less insulin responsive. On top of this, the hunger hormone ghrelin becomes hyper-secreted. Taken together, you end up with a body that is hungry and ready to store all your meals as fat. 

Bodily Decay

Finally, we end with an even worse consequence:

5. Lowered Testosterone/Estrogen: This point is one of the most important points to consider. For starters, low testosterone results in significantly smaller testicles. To make matters worse, due to the lowered levels of growth hormone, the lack of testosterone makes it very easy to lose lean muscle mass; the two main anabolic hormones within the body have just been switched off. Low estrogen is a problem for both men and women. Estrogen is what preserves bone tissue in both sexes (testosterone converts into estrogen within men’s bones). Due to the low levels of sex hormones, the risk of getting osteoporosis becomes much higher.

These risk factors only scratch the surface of issues related to reduced sleep. Problems ranging from altered gene expression to reduced memory capacity only make matters worse. The consequences are so dire that jobs involving shift work have been labelled by the World Health Organization as a probable carcinogen. This is all because of the simple fact that cutting down sleep duration is the most unnatural thing we can do to our bodies without regret.