Don’t sleep On This …
Hello, people! Welcome back to a brand new blog for a brand new year! It’s been a tough one for moi thus far, as I got the gift no one wants… covid. It’s been gnarly, but thankfully, I’m starting to feel more like myself again. This week, we’re starting a new series on a very important topic that I hear a lot of complaints about: sleep. Sleep is a vital part of life; we spend up to one-third of our lives doing it, and can’t live without it. It’s a lot like sex… everyone wants it, and some people get more of it than others.
Don’t Sleep on this…
Lots of go getters and workaholics will say “I’ll sleep when I’m dead.” But the problem is that that might be sooner than you want it to be if that’s your point of view. Why is this? Why is sleep so important? What happens in our bodies and brains during sleep? Why is it so hard for some people to fall asleep, while others are out cold before their heads hit their pillows? How can we get better sleep? How does sleep- or lack thereof- affect mental health? One of my patients recently told me about her latest sleepwalking escapades. What’s that all about? These are just some of the questions I’ll be addressing in this series.
We’ll start with the first question: why do we sleep? At the most basic level, it makes us feel better. A sleepless night usually leads to a dull, lethargic day, but a good night of sleep makes us feel more alert, more energetic, happier, and better able to function. It is as necessary as food, and one way to think about the function of sleep is to compare it to that life-sustaining activity, eating. Hunger is a mechanism that has evolved to ensure that we consume the nutrients our bodies need to grow, repair tissues, and function properly, and feeling tired essentially serves the same purpose. Eating and sleeping are not very different, and both are regulated by powerful internal drives. Going without food produces the uncomfortable sensation of hunger, while going without sleep makes us feel overwhelmingly sleepy. And just as eating relieves hunger and ensures that we obtain the nutrients we need, sleeping relieves sleepiness and ensures that we obtain the sleep we need. But the question remains: why is it necessary? What is the function of sleep?
Despite decades of research and many discoveries about other aspects of sleep, the question of exactly why we sleep has been difficult to answer. Scientists have developed several theories, but as is the case with so many human processes, it’s unlikely that a single theory will ever be proven correct, as sleep is necessary for many biological functions.
Inactivity Theory, aka Adaptive Theory
One of the earliest theories of sleep, sometimes called the adaptive or evolutionary theory, suggests that inactivity at night is an adaptation that served as a survival mechanism by keeping organisms out of harm’s way at times when they would be particularly vulnerable. The theory suggests that animals that were able to stay still and quiet during these periods of vulnerability had an advantage over other animals that remained active. For example, they weren’t killed by nocturnal predators and didn’t have accidents during activities in the dark. Through natural selection, this behavioral strategy of inactivity presumably evolved to become what we now recognize as sleep. But for every yin there’s a yang, and a simple counter argument to this theory is that it may be safer to remain conscious in a dangerous environment, in order to be able to react to an emergency. So there doesn’t seem to be any major advantage to being unconscious and asleep if safety is paramount. I mean, yeah, you’re less likely to be run over by a car, but it’s easier to be eaten if you’re just laying there, conveniently waiting for the predator to get you.
Energy Conservation Theory
The energy conservation theory of sleep suggests that a main purpose of sleep is to reduce a person’s energy use during certain periods when it’s inconvenient and less efficient to hunt for food. This is backed up in our biology, as research has shown that our metabolic rate is significantly reduced during sleep, by as much as 10 percent in humans, and even more in other species. According to this theory, sleeping allows us to reduce our overall caloric requirements by spending part of our time functioning at a lower metabolism. Although it may be less apparent to people living in societies in which food sources are plentiful, one of the strongest factors in natural selection is competition for, and effective utilization of, energy resources. The theory supports the proposition that sleep is a process of natural selection; we’ve evolved to sleep to expend less energy for a certain amount of time each day. And in fact, research suggests that humans getting 8 hours of sleep can produce a daily energy savings of 35 percent over complete wakefulness.
Another explanation for why we sleep is based on the long held belief that sleep serves to “restore” what is lost in the body while awake. The bottom line is that sleep provides an opportunity for the body to repair and rejuvenate itself, and many important processes happen during sleep. In fact, many of the major restorative functions in the body- like muscle growth, tissue repair, protein synthesis, and growth hormone release- occur mostly, or in some cases only, during sleep. There is a great deal of empirical evidence collected in human and animal studies to support the restorative theory. For example, studies have demonstrated that animals deprived of sleep entirely lose all immune function and die in just a matter of weeks. All of the “sleep when you die” folks should probably read that.
Other rejuvenating aspects of sleep are specific to the brain and cognitive function. For example, while we are awake, neurons in the brain produce adenosine, which is a by product of cellular activity. As long as we are awake, adenosine accumulates and remains in high concentrations. During sleep, the body has a chance to clear adenosine from the system, and, as a result, we feel more alert when we wake. In fact, the accumulation of adenosine in the brain is thought to be one factor that leads to our perception of being tired; scientists think that this build-up during wakefulness may promote the drive to sleep.
Brain Plasticity Theory
One of the most recent and compelling explanations for why we sleep is based on findings that sleep is correlated to changes in the structure and organization of the brain. This phenomenon is known as brain plasticity, and its connection to sleep has several critical implications. Simply put, this theory says sleep is required for brain function. Specifically, sleep allows your neurons, or nerve cells, time to reorganize. Sleep affects many aspects of brain function, including learning, memory, problem-solving skills, creativity, focus, concentration, and decision making. Ever have trouble remembering today something you did or said yesterday if you didn’t sleep the night before? That’s because sleep contributes to memory function. While you sleep, short-term memories are converted into long-term memories, and information that is not needed is erased, so as not to clutter the nervous system. In addition, when you sleep, your brain’s glymphatic system clears out waste and removes toxic byproducts from your brain which build up throughout the day, and this allows your brain to work well when you wake up. If you don’t sleep, these things don’t happen, so if it seems like your brain doesn’t work properly when you’ve pulled an all-nighter, it’s because it doesn’t… it’s full of waste and useless info!
What else is sleep essential for?
Not only is sleep needed for physical health, sleep is also necessary for emotional health. Sleep and mental health are intertwined: on one hand, sleep disturbances can contribute to the onset and progression of mental health issues, but on the other hand, mental health issues can also contribute to sleep disturbances. I will cover this in more detail in another blog, but during sleep, brain activity increases in areas that regulate emotion, and this helps support emotional stability. One example of how sleep helps regulate emotions occurs in the amygdala. This part of the brain, located in the temporal lobe, is in charge of the fear response- it’s what controls your reaction when you face a perceived threat, like a stressful situation. When you get enough sleep, the amygdala can respond in a more adaptive way, but if you’re sleep-deprived, the amygdala is more likely to overreact.
Sleep affects your weight by controlling the hunger hormones ghrelin, which increases appetite, and leptin, which increases the feeling of being full after eating. During sleep, ghrelin decreases because you’re using less energy than when you’re awake. But lack of sleep elevates ghrelin and suppresses leptin, and this imbalance makes you hungrier, which increases the risk of eating more calories and gaining weight. Research shows that chronic sleep deprivation, even as few as five consecutive nights of short sleep, may be associated with increased risk of obesity, type 2 diabetes, and other metabolic syndromes. In addition, sleep is necessary for proper insulin function and may protect against insulin resistance. Insulin is a hormone that helps your cells use glucose, or sugar, for energy. But in insulin resistance, your cells don’t respond properly to insulin, and this can lead to high blood glucose levels and eventually, type 2 diabetes. Basically, sleep helps keep your cells healthy so they can properly take up glucose.
A healthy and strong immune system depends on sleep, period. Research shows that sleep deprivation lowers immunity and can inhibit immune response, which obvi makes the body much more susceptible to germs. When you sleep, your body makes cytokines, which are proteins that fight infection and inflammation. It also produces certain antibodies and various immune cells during this “down” time, and together, these prevent sickness by destroying harmful germs. This is why sleep is so important when you’re sick or stressed, as during these times, the body needs even more immune cells. Having had covid recently, I can vouch for that.
While the exact causes aren’t clear, scientists have established a link between heart disease and poor sleep. It is associated with risk factors for heart disease, including high blood pressure, increased sympathetic nervous system activity, elevated cortisol levels, increased inflammation, weight gain, and insulin resistance.
The Centers for Disease Control and Prevention says the average adult needs 7 hours of sleep a night. During that time, the body repairs cells and tissues, restores energy, and releases molecules like hormones and proteins, while the brain stores new information and gets rid of toxic waste, and the nerve cells communicate and reorganize. Without these processes, our bodies can’t function correctly. It’s a lot for a body to do, so give it the time it needs to do it!
Next time, we’ll talk about more what happens while you’re sleeping. I hope you enjoyed this blog and found it to be interesting and educational. Please feel free to share it with family and friends. Be sure to check out my YouTube channel with all of my videos, and I’d appreciate it if you would like, subscribe, leave comments, and share those vids! As always, my book Tales from the Couch has more educational topics and patient stories, and is available in office and on Amazon.
Thank you and be well people!