Why do we sleep?

At first glance, “why do we sleep?” seems like such a silly question to ask. It’s obvious, we need sleep in order to 1) stay sane, and 2) to survive. We all need to rest and recover if we want to be as healthy, functional and successful as possible when we wake up every morning and face a new day.

But why exactly do we need to sleep, rest, and recover in order to stay sane and survive?

If you really think about it, sleep is an incredible phenomenon, and by diving deeper into the question “why do we sleep?” we can gain some important insight into how our bodies work, thus giving us more appreciation of the process of sleep, as well as giving us insights into how to better improve our sleep.

So, why DO we sleep? Why don’t we just continue on with our merry lives uninterrupted by this pesky process? Each cell in our body, throughout the course of our life, is always in the “on” mode, on “active duty”. It’s always doing things; synthesizing proteins, metabolizing compounds for energy, communicating with other cells, etc. It’s always on. But, since we as humans in total are nothing but a big clump of cells acting together in synergy, why are WE not always in the “on” mode, the “active duty” mode? The reason lies in the control center of the body, the brain. It turns out that, in order to be an effective control center, the brain needs specific periods of rest. Sleep is rest occurring in 4 consecutive stages followed by a stage called rapid eye movement or REM. REM is critical to successful sleep, and these cycles are often repeated many times at night. While our cells are always on, our brain rests. And since our brain is the master control center, when our brain rests, so do our vital organs and muscles.

Why does the brain do this? Well, the reasons are a bit unclear, but it is known that during these phases, very important things occur in the body. In a sense, the body’s repair mechanisms kick on during this process. The body recovers from the day’s activities and carries out certain vital functions: healing damaged cells, boosting our immune system, recharging our heart and cardiovascular system.

Not only that, but successful completion of adequate sleep cycles also helps the brain function properly by maintaining connections between neurons (i.e. preserving the neural network). Thus not only brain function, but also memory, is improved.

We can actually physically feel the repercussions of this “recharging” mechanism of sleep: when we experience a good night’s sleep, we feel refreshed and energetic (albeit usually with the help of a cup of coffee), and when we experience a poor night’s sleep or lack of sleep, we feel deeply fatigued, and can even feel depressed.

So, now that we have some understanding of why we sleep, how do we obtain good sleep? What factors are responsible for our quality of sleep? Why do we sleep at night?

Why Do We Sleep At Night? Circadian Rhythms

We each have a “master clock” which is a biological clock based on circadian rhythm. The clock is regulated by the suprachiasmatic nucleus (SCN) in the hypothalamus of the brain, which controls our biological state based on the incoming light that is processed through our eyes. However, the SCN doesn’t respond to all light equally, and it turns out that the SCN is particularly sensitive to a certain frequency of light, blue light. Blue light is the primary component of daylight from the sun. However, we also are exposed to blue light from artificial devices like LED lights, or the screens of electronic devices.

As light traveling to our eyes diminished, our master clock releases chemicals that trigger changes in activity levels in different parts of the brain in order to prepare us for sleep. This set of chemical reactions also sends signals to an area of the brain called the pineal gland to notify us that it is time to let our guard down and relax. The pineal gland, in turn, releases a hormone called melatonin.

Melatonin

Melatonin is not only a hormone, but also an anti-oxidant, and is found in all forms of life in varying concentrations. It is produced in the brain and helps regulate our master clock and our adaptation to light-dark cycles. During the daytime, the light that enters our eyes triggers a sequence of events that prevent this hormone from being produced, making us stay awake and attentive. During the night, darkness stimulates its production and helps us wind down.

The production and release of melatonin is thus critical for proper functioning of our biological clock and circadian rhythm. Anything that disturbs melatonin production and function can throw off our master clock, and thus impact our sleep. For example, using cell phones, computers, and tablets in the evening before bed makes it difficult for us sleep since we constantly perceive the blue light from these devices, which impedes melatonin production.

Light isn’t the only thing that affects melatonin production, however. Our environment, nutrition, toxins, and stress, all can impact how melatonin is produced and released in the brain. Thus, it is no wonder that, in a modern world where electronic devices and stress abound, most of us likely experience poor sleep due to an altered production of melatonin and/or alterations in melatonin signaling.

GABA

The SCN is responsible for regulating another region of the brain called the Ventrolateral Preoptic Nucleus (VLPO). The VLPO is a small cluster of neurons situated near the hypothalamus. Depending on the information received from the SCN and from our environment, the VLPO stimulates the production of a neurotransmitter known as gamma-aminobutyric acid (GABA). Just like melatonin, this neurotransmitter is involved with our sleep/wake cycles. GABA’s primary function is to reduce the excitability of our nervous system. However, while GABA can reduce the activity of our nervous system, external activity like physical activity can prevent the SCN from triggering the production of GABA via the VLPO.

Thus, blocking blue light is not enough to get a good sleep; it is necessary that before bed we stop working, exercising, or overthinking about our day. That´s right, when you are laying down thinking about all of the embarrassing moments of your day, or your stressful job experiences, you’re impeding the production of GABA.

While getting enough sleep is important, the quality of sleep also matters. So, once we do finally fall asleep, we need to ensure that we’re actually getting high-quality rest. Enter heart rate variability.

Heart Rate Variability

Heart-rate variability (HRV) is the variation in time interval between heartbeats. It is a complicated topic, beyond the scope of this post, but by closely monitoring our HRV, we can gain insight into our quality of sleep, and ultimately, our health.

From the moment we fall asleep we lose control over our motor and sensory systems. When this happens we enter into a state where our brain is at the mercy of our autonomous nervous system. The autonomous nervous system controls things that we normally don’t have to “think” about, like heart rhythm, digestion, breathing and more. The autonomic nervous system has two entities: the sympathetic, which is responsible for the acceleration of heart rate (e.g. by adrenaline), and the parasympathetic, which is responsible for heart rate deceleration.

To obtain the best quality of sleep, we need to ensure that these two parts of our nervous system are in balance. If there are imbalances, our HRV will be altered. For example, if we are stressed and constantly reminiscing over the hectic activities of our day, the sympathetic nervous system will dominate and our heart rate variability will be reduced. A reduced HRV can imply that we lack optimal sleep, are sleep deprived, and can even give us clues that something may be wrong with our health.

So, What Should I Do If I’m Not Getting Enough Sleep?

If you´re having trouble falling asleep, or feel like you aren’t getting the best quality sleep possible, here are ten things you can do right now to help:

1. Stop working at least one hour before going to bed: e.g. stop checking emails and working online etc.
2. Avoid physical exercise or strenuous activity at least two hours before bed.
3. Minimize any emotional activity a few hours before you lay your head on the pillows.
4. Eliminate sugars at night, including fruits.
5. Eat a big meal at most four hours before going to sleep (no later).
6. Relax your mind to wind down before bed by doing soft activities like reading a book, solving a crossword, doing yoga stretches, sharing time with your partner, or listening to music. These are activities that help the brain understand that it is time to sleep.
7. Reduce the entrance of blue light to our eyes at least three hours before going to bed. You can do this with eye masks (such as our Premium 3D Memory Foam Sleep Mask), and/or by placing blue light shields on your smartphones or electronic devices.
8. Eliminate all other light illuminations, e.g. from lamps. Even though they’re not a significant source of blue light, these light sources still can stimulate the brain.
9. Prepare your day in such a way that the most stressful activities, or those which demand the most energy, are reserved for the earliest part of your day (the farthest from bedtime).
10. Take a small dose of a high-quality melatonin supplement. You can find great quality supplements on labdoor.com, which is a third-party services that extensively tests supplements by a variety of brands to ensure accuracy and safety.

Improving our quantity and quality of sleep is the best strategy to enhance our health in both the short term and long term. In a world where we are constantly bombarded with stimulation (smartphones, social media, etc.), and experience an ever-increasing stress from our jobs and daily life, we must take extra precautions to protect our sleep, adopting habits that facilitate and improve our sleep. In the end, doing so helps make our body the best tool to reach any goal we desire.

Other Links & References

For more info on sleep and how to improve, see the links below which are great posts by Dr. Kirk Parsley, Robb Wolf, and Dr. Sarah Ballantyne (a.k.a. “The Paleo Mom”):

1. How We Are Wired To Sleep, Part 1
2. How We Are Wired To Sleep, Part 2
3. How We Are Wired To Sleep, Part 3
4. Trouble Sleeping?

Interested in our Premium 3D Memory Foam Sleep Mask? Check out our product page for more info.