Just woke up from a nap? Don’t worry, it might be the most productive thing you do all day!
In today’s Silicon Valley world-changing-esque age sleep is seen as two things depending on the day: unnecessary or … utterly essential.
How?
Well, let me give you an example.
Have you ever relaxed on your couch after a long Monday of work or school, finally glad to get some time off? Finally a small break. You’ve noticed that it's still early-ish to go to bed so you have decided to start watching an episode of a show you just started and maybe(if you’re feeling especially tired) make yourself a bag of popcorn.
Just one episode, and I’ll go to bed. Plus coffee will do the job. — The famous line we all have heard.
Next thing you know, you have watched 5 hour-long episodes, finished all the popcorn bags in your pantry, and have exactly 5 hours until you have to get ready for the next day.
Does this situation feel similar?
If the answer is yes, you are not alone. Our society has an incredibly unhealthy relationship with sleep, with more than 30% of adults and 66% of adolescents being constantly sleep-deprived (8). But what if I told you that the activity you spend a third of your life doing, sleeping, could be the sole most productive thing you do all day, strengthen your immune system, aid in memory consolidation, and maintain your clear reasoning (1).
To understand how this all works, we must first analyze what happens when we sleep.
Though it is hard to define exactly what sleep is scientists view it as a state of our consciousness necessary for our proper functioning during which parts of the brain remain active.
Until the 1950s, scientists presumed that our brain was almost completely inactive without sleep. It was commonly accepted that all of our neurons just shut down to rest before a new day of activity. However, recent research has shown that that is far from the truth; in fact, complex mechanisms that contribute to our well-being tend to occur during shuteye.
In order to comprehensively study sleep, scientists break down sleep into four main phases: NREM 1, NREM 2, NREM 3, REM. REM stands for “Rapid Eye Movement” and NREM stands for “Non- Rapid Eye Movement.”(3)
The NREM 1 phase occurs when we are just about to fall asleep and transition between our two flavors of consciousnesses, awake and asleep. During this period our brain releases lower frequency waves called alpha waves, our body temperature lowers, heart rate slows, and we eventually enter the NREM 2 phase.
During the NREM2 phase, muscles relax even further and brain wave activity winds down even more with the release of theta waves. Surprisingly, this stage is also characterized by sleep spindles, short bursts of energy in specific regions of the brain, usually in the hypothalamus. Though scientists do not yet know the significance of sleep spindles, hypotheses linking spindle activity with the strengthening of memory have been proposed. (9) As the NREM-3 phase begins, heart rate is at its lowest and muscle relaxation at its highest. NREM-3 is also the phase where involuntary sleepwalking and talking occur.
Lastly, we transition into REM sleep, arguably the most important part of our nightly routine. Just like the name itself suggests, our eyes move a lot under our lids. It is very common that we experience and “see” very vivid dreams during this period.
Thankfully, our brain stem blocks any messages of movement as a response to our dreams from going to our muscles, leaving the body in a state of paralysis.
Our frequency of brainwaves becomes much more rapid, and research has even shown that some areas of the brain such as the “temporal-occipital cortical regions, the hippocampus, and amygdala, exhibit activation comparable to that during waking.”
We shift between these four stages every 90 minutes or approximately three to four times each night. This cycle of dormancy is regulated by two main factors: our circadian rhythms and our molecular waste clean-up mechanisms. (1,2,4)
Our circadian rhythm is our internal alarm clock controlled by the hypothalamus which “responds to the cycle of the day and night.” The role of the hypothalamus, itself, is to connect the nervous system to the endocrine system which controls the hormones that regulate our behavior, consciousness, and even sleep. (10,11) The hypothalamus is home to suprachiasmatic nucleus cells, “the primary circadian pacemaker in mammals” that controls these rhythms based on synaptic input from other nerve cells in the body. (11)
They are connected to light-sensitive cells called photoreceptors in our retinas that detect light and report this detection of stimuli through our retinohypothalamic tract and tell our brain to sync up with the day and night cycle.
During the day, the detection of light stimulates the production of “awake hormones” such as cortisol. On the other hand, darkness stimulates the production of a sleep hormone called melatonin that makes us fatigued and sleepy.
There is also a wide belief that the build-up of chemical waste contributes to our feeling of tiredness. Why?
Well, during the day cells in our body break down ATP into usable chunks of energy used to perform daily mechanisms. When this process is conducted by our neural cells, adenosine, a neurotransmitter, begins to build up. These adenosine molecules bind to receptors throughout the brain that cause a series of chemical reactions that lead our neurons to fire more slowly and lead us to become more sleepy.
So now that we know how, let’s find out why we need sleep.
Though there isn’t a common consensus among researchers, there are many hypotheses that pose explanations as to why sleep is so important for us. It is very likely that the right answer to this question lies in a combination of some of these ideas while others will be disproven.
The Recuperation Hypothesis
This hypothesis is based on the idea that sleep is necessary for our mind and body to recover and rest. Studies have shown that genes associated with restoration and metabolic pathways are only or especially active during sleep which allows for functions such as muscle growth, tissue repair, protein synthesis, and growth hormone release to occur.
Sleep has also been associated with the removal of waste more efficiently than your body would at any given time. Our glymphatic system uses cerebral fluid to clear out toxic byproducts that accumulate between cells in the brain, such as adenosine, so we wake up feeling refreshed. (2)
Lastly, this period is seen as a time of rest for some of the most active parts of our brain. Our prefrontal cortex is the area of our brain dedicated to logical reasoning; to no surprise, this area is always active when we are awake. As a result, this time of our day serves as one where critical areas of the brain can wind down and replenish lost neurons.
Neuroplasticity Theory
On the other hand, scientists have proposed a connection between sleep and neuroplasticity. Neuroplasticity is the ability of the brain to undergo biological changes such as the formation, strengthening, or weakening of new synapses. MRI scans captured on sleeping study participants allegedly showed that these changes occur often when we sleep, especially during the REM phase. This acts as an explanation of why newborns spend a majority of their first years asleep, as this period supposedly allows their brains to grow and strengthen new connections. (2,7)
Memory and Learning Theory
Our memory enables us to retain and process new information, and essentially, makeup who we are. Memory has been broken down by psychologists into three main stages: encoding, consolidation, and retrieval. (6) Encoding is the process by which we input new information into our short-term memory such as the definition of a word, a list of numbers, or a particular moment of our day. During consolidation, this information is retained from short term memory and stored in long term memory. There, we are capable of accessing or retrieving these memories after long periods of time.
So, where does sleep come in, among all this? Researchers believe that brain electrical patterns during sleep are a crucial part of memory consolidation.
Dr. Matthew Walker is a scientist and professor of neuroscience and psychology at the University of Berkeley California, known for his book called “Why We Sleep.” In this New York Times Bestseller, he broke down the impact of each stage of sleep, deep sleep, light sleep, and REM sleep, in the process of memory consolidation, building upon the work of leading scientists on the field of memory and sleep. (1)
During the day incoming information stored in the short-term memory remains in our hippocampus, a part of the limbic system which is responsible for committing information from short-term memory into long-term memory. According to Dr. Walker, during deep sleep, bursts of electricity in our brain, sleep spindles, “ship” these memories from the hippocampus to the cortex, the layer of tissue in the top of your brain where these memories are long term stored. (1) This is important because the next day you will likely remember more information learned the day prior and attain more of the upcoming day. On the flip side of this, according to Walker, if you are losing out on a period of a deep sleep, much of what we learned the day prior would not be transitioned into the cortex and is likely to be forgotten.
Light sleep appears to be the period where all information that was “undelivered” or unnecessary will be cleared out. He compares this period to cleaning maintenance which prepares the hippocampus for a new day of learning.(1)
Lastly, REM sleep is the period when our brain goes through these “files” and makes sense of them. This intertwining of past and new memories leads to the formation of a vivid story in our mind called a dream. (1)
While trying to understand the importance of sleep, Walker put this hypothesis to the test. He studied two groups of participants, one which slept 8 hrs during the night and another which remained awake with no use of stimulants, such as caffeine, or naps. The next day both groups are placed under MRI machines and imaged while trying to learn a series of the same new facts. Those that slept demonstrated major activity in the hippocampus while those that didn’t, showed almost none. In the following two days, both groups went home and received 8 hrs of sleep. After these two days, participants were tested on what they learned two days prior; shockingly, those with no sleep remembered 40% less than the opposing group. (1,3)
Nevertheless, there are many researchers that support this general hypothesis but have different explanations that Dr. Walker. All perspectives in this area of research continue to deeper our understanding of sleep.
So what happens when we watch a few too many episodes and lose out on sleep?
Aha! I had to hold you accountable one last time!
A lot of what we know about the healthy brain comes from what we learn when things go wrong.
Studies have shown that after a night of little sleep, we are more likely to wake up tired and unrefreshed. This causes us to have slower brain effectivity and reaction time. (2)
Furthermore, our prefrontal cortex, one of the most crucial regions for reasoning, begins to function at a lower capacity, leading to a higher probability of poor judgment. (2) These are key factors as to why 70,000 car accidents in the US have been associated with tiredness and loss of sleep, more than those caused by drunk driving. (1)
With less sleep, we are also likely to experience a change in behavior… and not for the better.
The amygdala, the center of strong emotions and tells the body to prepare for danger, experiences a 60% increase in the responsibility with the decrease in sleep, resulting in increased impulsivity, anger, and paranoia. (2,5) Additionally, with our prefrontal cortex winding down, our brain uses a backup region called the Locus Coeruleus; this part of our brain responds instinctively to stress and consider nearly everything a threat which is why we tend to be “snappy” after pulling an all-nighter.
Unfortunately, these “symptoms” appear to just be the tip of the iceberg. One of the most surprising correlations that sleep loss has been correlated to is immune system suppression. Studies have shown that sleeping just four hours a night causes a reduction of natural killer cells, responsible for targeting sickly body cells by 70%. (2) Another study showed a 50% decrease in antibodies in participants who were “moderately sleep-deprived for a period of 7 days.”
While more than 300 genes responsible for immune system defense become less sensitive and lower protection, many responsible for the stimulation of inflammation, growth of tumors, and stress are upregulated. An experiment conducted by David Gonzal from the University of Chicago put this hypothesis to the test.
He injected a group of mice with cancerous cells; half of these participants slept normally each night while others had “disrupted sleep.” (1) Results showed that after one month, the group of mice that received fewer hours of sleep had a 200% increase in cancer growth compared to normal sleeping mice, with cancer reaching other parts of their body. (1) This is why the lack of sleep is classified as a possible accelerator for several types of cancers.
Lastly, the side effects of sleep deprivation appear to also have a negative effect on the success of students throughout the world.
A school in Edina, Minnesota moved the start of the school day from 7:25 AM to 8:30 AM. The year prior to this change an average of 1225 SAT scores was demonstrated by that year’s seniors. The next year, students that had undergone the same exact course but had been able to receive an extra hour of sleep each day received an average of 1500 SAT scores. (1) Though this study is not controlled, it is clear that that the amount of sleep a teenager receives have an impactful role on their wellbeing and success.
Tips for sleep
Now that we know the true importance of sleep, there are steps we can all take in order to improve our relationship with it.
1. Establish a Routine
Having a healthy sleep routine means attempting to go to bed at the same time each night and wake up at the same time each morning. Regularity will train the body to feel naturally sleepy and naturally awake at the same time each day.
2. Reduce Blue Light Exposure at Least 30 min Before Bedtime
This one, I am really guilty of! Our mind uses light-sensing cells to inform our circadian rhythm, blue light exposure before bed tricks our mind into thinking that it is still day. This halts the production of melatonin and therefore, our desire to sleep.
3. Drop the Temperature of Your Room by a Few Degrees
Physicians recommend lowering the room temperature by 2 degrees to fall asleep, aiming for 65 Ferenheight or 18 Celius. This is because a cooler environment will also lower our body temperature which is more suitable for our circadian rhythm.
4. Reduce Coffee Usage
Coffee is really a drug (not kidding)!
Remember the adenosine receptors we talked about earlier? Turns out that because of the similar shape of the coffee molecules to adenosine, they can inhibit adenosine from binding to receptors and prevent us from falling asleep.
Long term, our brain will develop more adenosine receptors in order to bind to the normal amount of adenosine, requiring a higher dosage of coffee to remain awake.
Put simply: caffeine messes with the natural chemical balances of our sleep cycle.
Conclusion
Though the majority of us have an unhealthy relationship with sleep, it is important to make an effort to change this. By embracing sleep and establishing a healthy relationship with it, you will live a healthier and happier life. From a stronger body to a more successful career, we must all prioritize our needs such as sleep, and maybe the blasting morning alarm will just be the sign of a new day full of hope and opportunities.
References
- Matthew Walker: “Why We Sleep: The New Science Of Sleep And Dreams” | Talks At Google. 2018. Video. Talks at Google.
- Why Do We Sleep? | Russell Foster. 2013. Video. TED.
- “The Science Of Sleep: Understanding What Happens When You Sleep”. 2020. Johns Hopkins Medicine.https://www.hopkinsmedicine.org/health/wellness-and-prevention/the-science-of-sleep-understanding-what-happens-when-you-sleep.
- “Sleep, Learning, And Memory | Healthy Sleep”. 2020. Healthysleep.Med.Harvard.Edu. http://healthysleep.med.harvard.edu/healthy/matters/benefits-of-sleep/learning-memory.
- The Science Of Sleep. 2018. Video. SciShow.
- Rasch, Björn, and Jan Born. “About sleep’s role in memory.” Physiological reviews vol. 93,2 (2013): 681–766. doi:10.1152/physrev.00032.2012
- 2020. https://www.hup.harvard.edu/catalog.php?isbn=9780674065857.
- Andrillon, Thomas et al. “Sleep spindles in humans: insights from intracranial EEG and unit recordings.” The Journal of neuroscience : the official journal of the Society for Neuroscience vol. 31,49 (2011): 17821–34. doi:10.1523/JNEUROSCI.2604–11.2011
- Welsh, David K et al. “Suprachiasmatic nucleus: cell autonomy and network properties.” Annual review of physiology vol. 72 (2010): 551–77. doi:10.1146/annurev-physiol-021909–135919