Do you think you had enough sleep last night?
Over this article series on Sleep as Nutrition, you may have a different opinion about your answer. The series will consist of 3 articles inspired by the world-famous book Why We Sleep authored by sleep scientist, Matt Walker. In this first part, we will look at an overview of the mechanics of sleep.
Sleep is as essential to us as breathing. We sometimes invest in learning the best breathing techniques to increase our longevity but only a few do the same exercise for sleep. We usually take our sleeping habits, sleeping patterns for granted owing to which 2/3rd adults throughout all developed nations fail to obtain 8 hours of dedicated sleep. In Matt’s words, he was fond of saying Sleep is the third pillar of health alongside diet and exercise but no sooner he had realized that Sleep is more than a pillar, it’s the foundation on which diet and exercise rest, weaken the foundation a little and you’ll receive way fewer benefits that could be otherwise achieved with the management of sleep.
To begin with, in a nutshell, a routine sleeping pattern of fewer than 6-7 hours per night can negatively affect your immune system, so much so doubling your risk of cancer, giving rise to more symptoms of anxiety and depression, be a major factor in causing diabetes and also increase the risk of coronary arteries being blocked leading to cardiovascular diseases. Shorter sleeping spans have such correlated patterns with a shorter life span that WHO has declared a sleep loss epidemic throughout industrialized nations. As a matter of fact, the United States faces more accident cases of drowsy driving compared to driving under the influence of alcohol and drugs.
In a very basic sense, sleep is a combination of two factors:
- A signal from the internal clock that is located deep within the brain which regulates the day and night rhythm and makes you feel sleepy or awake at regular intervals
- Sleep pressure that builds up when you’re awake and released while you’re asleep
But a few very common questions to ask would be:
How do you know when to sleep?
This internal biological clock is referred to as the Circadian rhythm. The part of the brain that monitors this rhythm is called the suprachiasmatic nucleus which is located in the hypothalamus, right above the optic chiasm (the spot where optic nerves coming from both eyes cross). This location is specifically the reason the brain catches onto the sunlight and darkness for resetting the biological clock. It also controls the desires of eating and drinking, moods and emotions, core body temperature, and also the release of various hormones.
Talking of hormones, Melatonin, also called the hormone of the dark is released by the pineal gland soon after dusk and basically marks the commencement, announcing that the sleep process should begin. As it gets late, the concentration increases and reaches a peak while sleep is in progress. As the morning light kicks in, melatonin starts to disappear as the pineal gland recedes the secretion. There is another hormone called adenosine, which is released as soon as you wake up and is accumulated each minute you’re awake. The longer you stay awake, the more sleep pressure builds up. High adenosine turns down the efficiency of wakefulness-promoting regions of the brain. This is what causes you to feel the irresistible sense of slumber you feel when awake for a long time.
These hormones and circadian rhythm govern how our sleep cycles change when we travel abroad. Since the advent of airplanes, we have acquired the ability to speed through time zones faster than our internal clock. The suprachiasmatic nucleus which regulates the circadian rhythm as we’ve seen before can only adjust up to one hour per day hence introducing a phenomenon called jet lag after we travel to a place in a different time zone.
Why do some people work more efficiently in the morning and some in the evening?
Giving in to the pressure of the society we live in, you must have realized by now what kind of a person are you? Morning (Larks), Evening (Owls), or somewhere in the middle. As a practice, Owls are mostly looked down upon because they usually wake up late and also perceived as lazy by their fellow colleagues, friends, and maybe family too. But surprisingly, this characteristic is genetically determined. Commonly 30% of the population is Owl type, 40% is Lark type and 30% are somewhere in between. Frankly, it is not possible for a person to ‘change themselves into a morning/evening person’ against their character. If you wake up an Owl way before his natural time to wake up, research shows that their pre-frontal cortex (part of the brain that controls high level thought and logical reasoning) is still disabled, in simple words switched off.
Why does caffeine delay sleep?
The brain has receptors sites where adenosine attaches and hence causes you to feel sleepy. Caffeine battles with adenosine for binding to these receptors and when that happens the receptors are not activated which causes you to feel sleepy. It blocks these sites for adenosine just like we put hands on our eyes to block vision. But since the hormone release isn’t affected, the adenosine keeps on accumulating and caffeine makes us feel alert even after high amounts of adenosine. It takes 5-7 hours for the body to remove 50% of the caffeine concentration, done by an enzyme in the liver. Hence when the effect reduces after hours, we feel an even stronger urge to sleep given the sudden activation of cumulative adenosine along with earlier sleep pressure. The picture shows how detrimental are the effects of various drugs on a spider’s ability to weave its web. Surprisingly, sleeping pills and caffeine have worse effects on coordination than severe drugs. Also, caffeine here refers not only to coffee but also caffeinated cold drinks, tea, dark chocolate, some drugs like pain relievers or weight loss pills.
Another common practice we follow is that of undertaking sleep debt and repaying it later. For example, toiling hard across the weekdays depriving yourself of essential sleep and oversleeping on the weekend. A sad but true revelation is that this doesn’t work out, in this case, the harm and benefits are reaped immediately after. The effects are experimentally confirmed for improvement in memory, productivity anxiety, and mood swings which we will see further in the series.
Stereotypical position, lowered muscle tone, no responsivity, and reversible timed pattern. This is how we casually identify a person who is asleep rather than assuming they’re dead. We lose all perception of the outside world as the Thalamus (part of the brain that relays sensory and motor signals) is in a complete blackout during sleep. While we sleep, all conscious mapping of time is lost and time feels dilated. Although surprisingly, you must’ve noticed waking up exactly before the alarm when you have an important meeting or flight the next day. This is because of the fact that unconsciously time is logged by the brain. And you were wondering how smart your brain is?
When sleep scientists record sleep data, they use brainwave signals (rhythmic or repetitive patterns of neural activity in the central nervous system produce electric waves translated into waves), eye movement activity, and muscle activity to monitor and collect observations. Experimentally determined, there are two types of sleep: NREM (Non-Rapid Eye Movement) and REM (Rapid Eye Movement). Within the 8 hours of recommended sleep, the first half is dominated by NREM sleep (divided into four stages, where stage 3,4 are deep sleep stages), and the second half is dominated by REM sleep. However, there is a reversal at every 90 mins duration. Because of this uneven spread of sleep over the night hours, if you’re sleeping at midnight and you wake up at 6 am instead of 8 am, logically you lose 25% of your sleep but in a real sense, you’re losing out on 60-90% of your crucial REM sleep.
Sleep essentially elegantly remodels and updates neural circuits at night. Memory management in the brain has a limited capacity, hence sleep is the tool that is used to balance the retention of some old memories and having enough room for new information. In simple terms, NREM sleep is responsible for weeding out and removing unnecessary connections and REM sleep further strengthens the connections that remain. NREM sleep stage 3 and 4, also called deep slow-wave sleep is the stage in which the Thalamus is close to nocturnal cerebral meditation (different from wakeful meditative states). Wakefulness is more related to the reception of information and NREM to the reflection on that information. However, astonishingly REM sleep waves resemble waves generated in wakefulness, it is almost impossible to distinguish between the two by just looking at the wave diagram. So much so, some brain parts are 30% more active in REM sleep than while awake. This is the reason why REM sleep is also called paradoxical sleep since the brain acts like it is awake but the body is paralyzed. This the brain’s trick to save the body from acting out the dreams, this state is called atonia (muscles lose all tone and strength). This time is especially involved with past experiences, innovative insights, and problem-solving. Experiments have suggested that deprivation of REM sleep can result in a reduction of problem-solving capacities of the individual by up to 40%. Now you can finally understand the reason behind ‘Let me sleep on the problem’ actually brings out some novel solutions. REM sleep also increases our ability to build better relations by improving emotional intelligence and stirs creativity to think differently when faced with uncommon situations.
Across the life span, there occurs a significant change in our sleep. While in the womb, the fetus is mostly asleep switching between NREM and REM sleep state, until the last 2 weeks of pregnancy where it generates a lifetime REM sleep high of 12 hours. It is exceptionally important for synaptogenesis (creation of millions of neural wiring links, synapses). Also, fun fact, the kicks, and movements noticed during pregnancy are actually because the brain hasn’t yet developed the muscle paralyzing system during sleep and the baby is peacefully asleep while everyone celebrates. If due to any circumstance the fetus is deprived of the REM sleep, it increases the chances of acquiring autism spectrum disorder and some other brain diseases. The major reason behind these diseases is abnormal synaptogenesis or genetics. An infant’s sleep is not governed by rhythm and they have a polyphasic sleep, while they grow and reach the age of 4-5 years, their sleep because biphasic as you might have noticed. Also the ratio between NREM and REM changes from 1:1 (6 months old), to 7:3 (5 years old) to finally 8:2 (late teens). In the case of teens as well, NREM sleep helps in maturation of the brain increasing cognitive ability and rationality manifold. The circadian rhythm of younger children runs earlier but as they grow up to mid-teens, the circadian rhythm again shifts as they need more sleep and at different times than their parents. Researchers advocate that this shift is socio-evolutionary in nature that happened to operate independently as a peer group collective. In old age and midlife, fragmentation of sleep starts to occur due to an early shift in circadian rhythm due to work routines and also due to weakened bladder in some people. As we grow old, all parts of the brain do not degenerate equally (atrophy) and the first regions to get affected ae the deep sleep producing regions, and an individual may lose up to 70% deep sleep compared to a young adult.
In this article, we read about how different stages of sleep act as different nutrients in our food, and missing out on even a single aspect can keep us from getting the maximum benefit for our body and our mind.
