Lights out

I never sleep, cause sleep is the cousin of death

Nas, N.Y. State of Mind (1994)

In a series of experiments during the 1980s and 1990s, psychiatrist David Dinges and safety specialist Mark Rosekind showed that naps help minimize mental fatigue and attention lapses. They worked for the US Federal Aviation Authority (FAA), looking into ways to prevent lapses of concentration in pilots during long-haul flights that could lead to catastrophic events. Specifically, their experiments indicated that a nap before a long period of sleep deprivation acted as a buffer protecting the pilots’ brains from extreme fatigue. Whereas the FAA wanted to implement these “prophylactic naps” as policy among aviation pilots, they had to figure how to brand this safety regulation in an appealing way to leadership-based jobs. The “power nap” was born.

In his book Why We Sleep, neuroscientist and psychologist Matthew Walker (aka the “Sleep Diplomat”) presents a 360 degrees-view on why we sleep, accompanied by science and its history. These are some important take-home messages:

Sleep cycles

Our brain has a clock, the suprachiasmatic nucleus, which uses light to adjust our circadian rhythms into a 24-hour cycle. First, the suprachiasmatic nucleus instructs the pineal gland to release melatonin soon after dusk. Hence, melatonin signals it’s getting dark. Second, melatonin concentration decreases overnight until finally, with the dawn, the light indicates the pineal gland to stop its release. When you travel to a different time zone, your suprachiasmatic nucleus needs about one day to adjust for every hour difference (e.g., it takes me about a week to adjust every time I fly to Barcelona from New York).

Besides our 24-hour circadian rhythm, our wake/sleep cycle is also determined by the amount of “sleep pressure.” Walker defines it as a barometer registering the elapsed time since waking up. This is controlled by the accumulation of adenosine in the brain, which increases our desire to sleep. Of course, we can fool our system using the most popular psychoactive stimulant worldwide. Coffee mutes the sleep signal by blocking the adenosine receptors. However, the urge to sleep doesn’t go away. Adenosine just piles up until your liver decomposes the caffeine in your system. Welcome “caffeine crash.” At this point, most of us will fight back with more coffee, forever maintain a perfect dependency cycle of sleep-deprived wakefulness.

Sleep types (NREM vs. REM)

Strange things happen when we sleep. Sometimes we close our eyes, then we open them again, just like a several-hour-long blink of an eye. There is nothing in-between. Sometimes we experience the craziest adventures, fall from precipices, our teeth fall, years pass before the next morning. This is how we experience “non-rapid” vs. “rapid eye movement” sleep (NREM and REM sleep, respectively).

When we are awake, our brainwave activity reflects the continuous reception of the outside sensory world. During NREM sleep, our brain activity denotes a slow wave pattern. It is a period of inward reflection, fostering information transfer and the distillation of memories. And the REM sleep? Walker explains that brain activity during REM sleep is an almost perfect replica of that during alert wakefulness. In fact, some parts of the brain seem to be even more active during REM sleep than when we are awake. It seems that during REM sleep, our brain is recounting the activities of the day. Why we move our eyes during REM sleep? Some studies suggest that they are related to the change of scenery when we dream (also in blind people).

During NREM sleep, consciousness seems to vanish. But somehow, our brain clock still counts the pass of time. That’s how sometimes we wake up a few minutes before our alarm is about to go off. On the other hand, during REM sleep—the dream state—we experience the pass of time, but often time is stretched out relative to “real” time. This phenomenon—time dilation—could be explained by the slowdown in neural time activity events during REM-sleep dreaming. We also dream during NREM sleep, but “real dreams” with a narrative (we move, hallucinate, we get emotional) come from REM sleep. Walker argues that the NREM-REM sleep interplay (they alternative every 90 minutes) is necessary to remodel and update our neural circuits, hence managing the finite storage space in our brains.

sleep was the first state of life on this planet, and it was from sleep that wakefulness emerged.

Matthew Walker, Why We Sleep (2018)

Sleep (and human) evolution

And the starting point of sleep was NREM. Only birds and mammals have (independently) evolved a “full-blown” REM sleep. Exceptions are mammals secondarily evolved to live in the aquatic environment. One more weird thing about REM sleep: During this dream state, our voluntary muscles are completely paralyzed. Hence, it makes sense that dolphins and other cetaceans don’t REM-sleep, or at least in the same way as we do, they would drown.

We sleep less than other primates (~8 hours instead of 10-15 hours), but our REM sleep is disproportionately larger (20-25% of our sleep time compared to an average ~9 % in other primates). Walker argues that increased REM sleep in the human lineage originated with Homo erectus in relation to tree-to-ground sleeping. On the one hand, it became safer to REM sleep without risking falling from the tree. On the other, predators made sleeping on the ground life-threatening dangerous for H. erectus. The solution to this compromise? Less sleep, but of higher quality. Continued research identifies the diverse array of life processes mediated by REM sleep (e.g., cardiovascular health, body-temperature regulation, emotional restoration, memory association, creativity). Hence, Walker proposes that this REM-increased shift facilitated our enhanced level of sociocultural complexity and cognition.

Modern life habits are disrupting our natural sleep. The Sun’s schedule is disrupted in our homes (certainly in most cities) with electric lighting, which has a melatonin-suppressing influence on our brain and thus our sleep. Especially disrupting our sleep are the blue light-emitting diodes (blue LEDs) present in our beloved smartphones and tablets. For example, using an iPad for two hours before bed blocked melatonin levels by 23%.

Shuji Nakamura, Isamu Akasaki, and Hiroshi Amano won the 2014 Nobel Prize in physics for the invention of blue LEDs in 1997. However, they didn’t consider a key aspect of our biology. Human eye light receptors communicating daytime to the suprachiasmatic nucleus are more sensitive to blue light (i.e., it produces more nighttime melatonin suppression) than warm yellow lights from traditional bulbs. Why? Evolution: We might be especially sensitive to blue light due to our distant ancestry as marine dwellers. Ocean water looks blue because it filters for the warmer (yellow, red) wavelengths in the visible spectrum. Fortunately, there is software available to reduce the amount of harmful blue LED light on our screens.

Dreaming

In his 1899 book The Interpretation of Dreams, psychoanalysis founder Sigmund Freud situated dreams within the brain, first making them a domain of what later would be called “neurosciences.” Until then, dreams were considered celestial beings. Freud himself believed that dreams came from unconscious wishes that had not been fulfilled. However, in 1983, Francis Crick (co-discoverer of DNA’s helical structure) and Graeme Mitchison presented a more testable hypothesis: REM-sleep dreaming removes unnecessary information in the brain (what they called “parasitic memories”). Walker’s research confirms this idea to a degree, except that it points to NREM sleep as responsible for remembering/forgetting by transferring newly learned information into long-term safe storage brain sites. As for REM sleep, Walker’s research suggests that dreams are not a by-product of REM sleep but the essence. Dreams, he argues, have two primary functions:

REM-sleep dreams help to separate emotions from past experiences

This is the reason why we can recall our strongest memories from childhood without reliving the same emotional degree attached to them. Studies by neuroscientist Rosalind Cartwright have shown that dreaming about the emotional themes and feelings of past traumatic events (including PTSD) can be used as a healing tool to treat and resolve past conflicts.

REM-sleep dreaming fuels creativity

Once NREM-sleep organizes our new memories. REM sleep builds associative networks with the pre-existing pieces of information in our brain. This is the reason why we can wake up with bright new ideas and solutions to old problems after a good night of sleep. During REM sleep, the brain stem releases acetylcholine indiscriminately, ramping up electricity levels across the brain. Consequently, associations among stored memories are triggered in a disorganized way, creating hallucinations (i.e., dreams). Sometimes, the brain accidentally produces a new link, perhaps a solution, that had escaped our conscious mind. Dreams explore uncharted territory.

REM-sleep dream is serious business. No wonder requires the participation of both sides of the brain (at the same time, and to an equal degree).

Less sleep (less life)

Brain healing impairment

In the same way that your lymphatic system drains the contaminants from your bloodstream, the glymphatic system (made of glia cells) cleanses your brain from the metabolic contaminants produced by the neurons. This neural sanitization works at its full during sleep, especially during deep NREM sleep, by bathing the brain with cerebrospinal fluid. From this, Walker concludes that the less we sleep, the more likely we are of developing Alzheimer’s disease.

Body repair impairment

You and I can have the same chronological age, but one of us can be biologically older. One of us can look older, feel older, and die younger. Differences in biological age are reflected in telomere length, which is shorter in the one that is “older,” the one of us who sleeps less. Messing with our sleep can also increase the chances of developing some cancers.

Short memory impairment

In addition, sleep deprivation damages the hippocampus, a brain region involved in learning new things (have you watched Memento?).

Food-satiety impairment

Sleep deprivation will make you eat more. The reason is that it increases our blood levels of endocannabinoids. Just like using marihuana, we’ll get the munchies.

Sex impairment

Sleep loss is statistically associated with lower testosterone levels and smaller testicles.

Productivity impairment

Under-slept bosses are less charismatic and less capable of inspiring their team members to do their best work.

Decision-making impairment

If we don’t sleep well, we are less prepared to make the right decisions and act according to them. When it comes to our emotions, Walker compares the amygdala with our gas pedal and our prefrontal cortex as the break. After a good night of sleep, there is a balance between the two, and we can make our most emotionally sound, rational decisions. Without enough quality sleep, we become puppets of our own impulses (no bueno).

Why then do medical professionals have to endure stupidly long shifts? This likely increases the chances to make critical mistakes that cost lives. Answer: Since the 1880s, we are blindly following the steps of Dr. William Halstead, a father of modern medicine—a cocaine addict.

I believe it is time for us to reclaim our right to a full night of sleep, without embarrassment or the damaging stigma of laziness. In doing so, we can be reunited with that most powerful elixir of wellness and vitality, dispensed through every conceivable biological pathway. Then we may remember what it feels like to be truly awake during the day, infused with the very deepest plenitude of being.

Matthew Walker, Why We Sleep (2018)

More sleep (better life)

Sometimes, sleeping feels like “wasted time.” The lights go out, and we are not doing things we like to do: from binge-watching our favorite TV show to liking each post in SM or working on our important project. We try to fool our systems with caffeine (and other substances), to stay awake until late and wake up early the next morning to do more. Why we do this to ourselves?

Sleeping is often seen as a sign of laziness. Those who want to be perceived as hard-working, strong individuals would often brag about how little they sleep and how long their working hours are. Social pressure against sleeping is so strong that it affects the words we use for something as basic as having a siesta. Sleeping less is not a superhero’s quality. It’s irresponsible. Just like trying to work with a power tool at the end of its battery life is not the best idea. It is our duty to try having healthy sleep routines, to stay strong, to stay sharp. We consider sleeping a privilege, but keeping good sleeping practices* really is as fundamental as drinking and eating. It keeps our emotions and rational mind in balance, allowing us to feel happy and be more productive.

The life that we live when we are sleep-deprived is not full. Every adult needs to sleep ~7-9 hours/day. It is not just about us. It’s not just about our own health, mood, creativity, and productivity. It is also about the impact that this has on the well-being of those around us (do you like to hang out with a cranky person?). Protect your sleep. Your life depends on it.

* The Sleep Diplomat recommends the following sleeping practices:

• Maintain a slightly cold bedroom temperature (~65 degrees Fahrenheit; ~18.3ºC).

• Have a hot bath/shower before bedtime. When you get out of it, your core temperature will diminish, making you feel sleepy.

• Have siestas. Naps allow us to bring back our natural biphasic sleep and supplement with necessary sleeping time. The world would be a better place if we were all napping more.

and, especially:

• Go to bed and wake up at the same time every day, no matter what. Find the rhythm that works for you and stick to it. We cannot catch up on sleep on the weekend (irregular sleep negatively impacts our circadian rhythms). Sleep enough every day (enter naps).

Remember: We cannot cheat the system. Having a drink or two should help us get to sleep. However, alcohol does not make us sleep. Walker argues that similarly to sleeping pills, alcohol only anesthetizes our brain. It could resolve a crisis, but it’s not a long-term solution. Furthermore, booze fragments our sleep and often suppresses REM sleep, but not REM-sleep pressure: REM-sleep dreaming is so essential for our function that in hardcore alcoholics, REM dream-like hallucinations can explode in the middle of the day as “delirium tremens.”

Thanks to Matthew Walker for being the Sleep Diplomat that the world needs.

Cover image by Free-Photos from Pixabay.