Why Humans Don’t Get Enough Sleep

We spend a third of our lives sleeping, and at lest that much worrying. However, most of us know very little about sleep and stress, and even less about how the two relate. Many people, myself included, have observed that when we are under stress and need sleep the most, it is actually very hard to fall asleep or stay asleep. This had been the extent of my knowledge on the subject before I read “Why Zebras Don’t Get Ulcers” by Robert Sapolsky. In this book Sapolsky explains in detail the mechanisms of sleep, and how it is affected by stress.
Sapolsky describes our sleep as a complex cyclic structure that is comprised of several stages, each serving a specific purpose. He explains that stress activates the sympathetic nervous system and causes the level of glucocorticoid, which is a stress hormone, to go up. Sleep deprivation is a stressor that causes an increased secretion of stress hormones. Also, stress itself is a disruptor of sleep. I have been caught in this vicious cycle several times. Some of my insomnia experiences have been strange, some rather scary. Sapolsky’s book helped me to understand sleep and stress better. I will share some of my insomnia experiences and go over the main points of Sapolsky’s explanations.
I have a personal interest in the subject of stress-related sleep problems because I have had several episodes of stress-induced insomnia, two of them quite serious. Once, when I had a visa problem, now happily resolved, I could not get more then one or two hours of poor quolity sleep per night. Some nights I could not sleep at all. After a week of such severe sleep deprivation the whole world appeared a confusing dream. Some places seemed familiar but somehow different, and I could not remember how I got there. In fact, I could not remember much of anything; my short-term memory was disrupted. I was cold and disoriented all the time. For several days I existed in some bizarre frozen wonderland. I no longer was able to tell the difference between dream and reality. This experience scared me a lot, but it also made me interested in sleep problems.
Sapolsky engaged me in his book from this very first paragraph:
“It’s two o’clock in the morning and you’re lying in bed. You have something immensely important and challenging to do that next day – a critical meeting, a presentation, an exam. You have to get a decent night’s rest, but you’re still wide awake you try different strategies for relaxing – take deep, slow breaths, try to imagine restful mountain scenery – but instead you keep thinking that unless you fall asleep in the next minute, your career is finished. Thus you lie there, more tense by the second.”
I recognized myself in this description. Later in the chapter dedicated to sleep and stress, “Stress and a Good Night’s Sleep”, Sapolsky has answered most of the questions I had about the subject. Unfortunately, the solutions he offers are not simple or even always avalible.
Robert Sapolsky is a professor of biology and neurology at Stanford University. In his book, “Why Zebras Don’t Get Ulcers”, he investigates how stress affects our bodies and minds. Sapolsky states that prolonged stress can have a negative effect on our physical and mental health, causing cancer, heart disease, depression, ulcers, memory loss, and – not surprisingly – loss of sleep. When we worry about final exams, deadlines, and presentations, our bodies have a stress response similar to that of a zebra, being chased by a lion. However, that chase is over in minutes one way or another, while we can be stressed over our problems for days and weeks. We can literally worry ourselves sick and sleepless. Stress affects our sleep causing decrease in both quantity and quality of sleep.
Our sleep is a complex process; it is not a homogeneous phenomenon. It is comprised of three different stages – shallow sleep, when we are easily awakened, deep or slow wave sleep, and Rapid Eye Movement (REM) sleep, when we dream. These stages occur in cycles – we start off shallow, then go to deep sleep, and then to REM, and then we repeat the cycle approximately every 90 minutes. These stages serve different purposes and are characterized by different brain activities.
Our rest and energy restoration occurs mostly during the slow wave sleep. For the duration of this stage brain activity slows down, except for the regions involved in consolidation and retrieval of memory. On the other hand, during REM sleep there is an increase in brain activity. Some brain regions become even more active then when we are awake. The regions responsible for muscle movement, emotion, memory, and sensory processing – all increase their metabolic rate. However, activity in the frontal cortex, which is responsible for logical thinking, goes way down. This explains why our dreams are illogical and non-sequential.
Both slow wave and REM sleep are very important for us. They play a central role not only in our rest and energy restoration, but also in the formation of new memories and the consolidation of information from the previous day. They facilitate problem solving. This explains why my memory was so disrupted when I had insomnia.
During the slow wave sleep the sympathetic nervous system shuts down and the glucocorticoid level goes down. Hence, if we are sleep deprived, this decline in the levels of stress hormones does not occur. In fact, their level increases. This means that sleep deprivation is a stressor. The elevated levels of glucocorticoid caused buy sleep deprivation disrupt formation and consolidation of memory. Many of us, including myself, have tried to study for an exam the whole night only to realize that during the exam we can not recall anything we learned.
One of my insomnia episodes occurred during the last two weeks of a winter semester in my university back in Russia. Traditionally in Russian universities between 90 and100% of the grade is determined by the final exam. It makes the final week extremely stressful. The fact that the final grades determine the amount of financial aid a student is eligible to only make the stress worse. I had only one night to study for my last final. After a whole week of being sleep deprived and studying for abut twenty hours strait before the final my mind was completely blank. My head felt like it was filled with cotton. I remember thinking that now I know how stuffed toys feel. I could not concentrate, could not think, I was just stupidly blinking my eyes. It was a very embarrassing experience. I failed the final, and could not sleep normally for a while after that.
The lack of sleep activates stress response, and an activated stress response causes less sleep or low quality of sleep. It sounds like a never-ending vicious circle, but it is not. Actually, sleep deprivation does not cause a severe stress response, and eventually the need to sleep will overcome even the worst of stress-induced sleeplessness. This is what happened to me in both cases of my insomnia. However, even knowing that eventually I will collapse and get a restful night of uninterrupted sleep, I do not want to repeat an insomnia episode.
Unfortunately, there is no simple, universal solution to the problem of stress, and stress-related loss of sleep. However, I have learned that the situation is far from hopeless. We have to realize that generally the things we worry so much about are just isolated episodes. The problems will be resolved as my visa problem or failed final exam were. Now they seem so inconsequential that it is hard to understand why I was so stressed that I could not sleep. After all I was not chased by a lion. It is also important to gain some measure of control over the situation because the lack of control is a major stressor.
Getting control over a stressful situation or persuading ourselves not to worry about it is not always possible. However, there are some things that we can always manage. For example, regular exercise reduces stress and actually makes you feel good. In general, we should find something that gives us pleasure and relives our frustration. For me it is painting. Since I have discovered painting, I have not had any severe insomnia episodes.
In 1910 Americans averaged nine hours of sleep per night. Now on average we sleep 7.5 hours, and the number is dropping. The modern life is both stressful and exiting. It provides us with numerous ways to make ourselves stressed and sleep deprived. Now it is especially important to educate ourselves about sleep and stress to reduce our likelihood of getting such stress related diseases as ulcers, cancer, and cardiovascular disease. Moreover, if we do not worry about final exams, relationship problems, and missed essay deadlines, and sleep well instead, we will be able to resolve our problems easier and faster. And if you can not stop worrying, just think how you would explain your fear of public speaking to a zebra that is being chased by a lion.