Sleep IV
Source : infoplease.com
Since I am re-reading this book, I recognise so many patterns in myself and in people I know that could be related to sleep deprivation. Of course there are many other factors affecting us every day, but i had never considered sleep to have a major role in it. I knew it was important, but I did not know it was this important. Somewhere i the book Matthew says, he always knew that sleep was one of the three pillars of a healthy lifestyle others being - a good diet and frequent and correct exercise. As he worked through is research in the of neurosciences and sleep specifically, he realised that even the other two pillars of good health : diet and exercise and dependent upon sleep. Without good quantity and quality of sleep, diet and exercise aren't going to contribute to your body and mind as much as they can. So people, listen up and start sleeping - we all in our modern lives are chronically sleep deprived and it's time we sat up and took notice and corrected this very steep downward slope we are on.
This is a light post on the history of sleep and who sleep and how much. Sleep, Matthew says, might be the first state of life on this planet and it was from sleep that wakefullness emerged. Every anima; species studied sleeps. Worms, that first emerged 500 million years ago, and predate all vertebrate life, also slept. What are the key differences in the way organisms and animals sleep? Below are a few categories explained.
Total Amount of Time
You would like that it would be easy to work this out if given the body type, size and other such details about an animal - but it isn't that easy. There are cases of identical sleep times in very different family groups. The only thing Matthew says night make some logical sense is the complexity of the nervous system relative to the size of the body - a complex nervous system one demanding more sleep. But he immediately tells us this may not be a rule because the opossum which weighs the same as a rat sleep for 18 hours of day, with the rat sleeping 19 (the longest sleep duration in the animal kingdom). Then scientists thought maybe quality was key and not quantity. Maybe those that sleep less, have deeper sleep. Alas, that did not hold true to scientific study as well because mostly deeper sleep was associated with animals that also slept more. There was no clear definite reason and explanation. Instead these might be possible reasons for the quantity of sleep an organism requires
- Demands of waking survival : obtaining food, minimizing threat risk etc
- Serving the restorative physiological needs of an organism
- Tending to social requirements of the community.
Composition
This relates to stages of sleep - NREM and REM as well as dreaming. REM sleep supposedly evolved much later in the history of organisms, mostly to support functions that NREM couldn't achieve by itself. However even then, there are some species - ocean based- that do not have any REM, like whales and dolphins. Matthew says, this makes sense of course since REM is characterised by loss of control on voluntary muscles - which for species that need to swim continuously isn't all that great.
If mother nature has not astonished you with her immensely kickass capabilities already, here's another fact. Partially aquatic animals that split their time between land and water have both NREM and REM sleep but they stop having any REM sleep when they get into water, but it comes back when they are back to living on land.
If some animals can do without REM sleep, can we do that as well. If not, which kind of sleep is more important and what do we need more. Interesting questions that have lead to many experiments in birds, animals and humans where organisms were put on a diet of sleep to observe which one their system will crave more when given the opportunity to sleep. Here are findings:
- Sleep duration is much longer on the recovery night than a standard night.
- NREM sleep rebounds faster than REM sleep on the first night after total sleep deprivation. But if you were to record the 2nd and 3rd nights you'd notice a reversal - REM sleep now gains prominence and tries to get a larger share of the sleep pie.
- Both stages are therefore important!
- Regardless of the recovery opportunity, the brain never gets back sleep that it has lost. A scary scary thought for most of us who try to make-up for sleep on the weekends after depriving our bodies through the week.
The manner in which we sleep
- Unihemispheric: Dolpins & whales sleep with one half of their brains awake - one half of the brain continues the movement that is necessary under water. The two halves of the brain can function separately - once one side has gotten its quota of sleep, the other snoozes. Matthew correctly says "Sleep is non-negotiable". Bird do this too, they sleep with one half of their brain awake and hence the corresponding eye open - this helps with threat detection. But this is only NREM sleep. REM sleep is not capable of such division within the halves of the brain - the entire brain indulge sin deep REM sleep.
- Humans do a version of split NREM sleep when we are in new environments for example in a hotel room or unfamiliar sleeping environment. But not in a degree to which birds and dolphins do it.
Rare Exceptions
Matthew says in extreme situations, an individual will give up the need for sleep - in the case of starvation for example. "Individuals who are fasting will sleep less as the brain is tricked into thinking that food has suddenly become scarce." He goes on to give us two examples ;
- Female killer whales and their new born calves: The birth takes place away from the pod and post birth the calve and the mother swim back to the pod - neither of them sleep. This is completely opposite to the needs of a new born infant - because the highest demand and consumption of sleep happens in the first few months post birth.
- Birds : During transoceanic flights birds do not sleep - they catch mini naps lasting a few seconds to avoid the terrible effects of sleep deprivation. The example Matthew gives us is the white-crowned sparrow which during the year long migration does not sleep at all and does not face any consequences of it as well. But if you were to deprive the same bird of sleep when it is not migrating, there are neural and physical dysfunctions
The next section is one of my favorites in the book. My brother and I grew up sleeping in the afternoon. Our mother would make sure we slept for an hour before we sat down for homework and then evening pay time (and then more homework!). So I thought everyone grew up like this - but apparently not. Sadly as we grew up this practice slowly stopped - adult lives hardly allow you to nap in the afternoon. What is sadder is that if you do have the luxury to do this, you're often labelled lazy and this practice is seen as useless or a waste of time.
After I'd read Matthew's book, I realised we had yet another thing to add to the list of things to thank our mother for. Most adults, he says, sleep in a monophasic pattern: we sleep in a single long bout at night.
However, cultures that are untouched by modernity - Gabra tribe in Kenya or the San people in Kalahari desert - sleep in a biphasic pattern, taking a 30-60 min nap in the afternoon.
Another important point Matthew brings up is that even if these tribes were to sleep in a monophasic pattern, their bedtime are significantly different from modern societies. They fall asleep 2-3 hours after sunset and and awake up with the sun - therefore the term midnight actually means middle of the night. In the lives we live, we are not only not getting a full 8 hours of sleep in the night, we are even forgoing the afternoon naps that are deeply beneficial!
There is a reason we experience a dip in alertness post meals in the afternoon (also called post prandial alertness dip) - it is a part of our daily rhythm. Matthew then quotes a research where the team focused on cardiovascular health of the Greek adults as the practice of an afternoon nap comes to an end. Sadly, there was a 37% increase in chances of death due to a heart disease in folks who abandoned the practice, as compared to those who regularly took afternoon naps.
Humans evolved to be a unique creature due to our cognitive abilities, our socio cultural networks, our creativity. Matthew says these are all characteristics that are nourished by sleep. Not any kind of sleep, but REM sleep in particular. On average most primates experience 9% REM sleep in their total sleep duration, whereas human get a massive 20% of REM sleep - this is in spite of sleeping much less (in quantity) than these other creatures.
Matthew goes onto to say that this distinguishes us in two ways:
- REM increases our degree of socio-cultural complexity : it fine tunes the emotional circuits of the human brain. Further, it increases our ability to recognise & navigate socio-emotional signals. It facilitates accurate recognition & comprehension, which allows us to make rational decisions in a cool headed manner. This has enabled the creation of large, emotionally stable, highly bonded & intensely social communities if humans - which we all know is the game changer in the why humans won the race of being the dominant species on this planet.
- REM-state dreaming fuels creativity: "NREM sleep helps transfer and make safe newly learned information into long-term storage sites of the brain". But it is REM sleep that takes these new memories and connects them to older information that then spark creative insights and allow the construction of vast networks of information in the brain.
REM sleep therefore is truly responsible for our "rise as a globally dominant social superclass"
It is hence astonishing that we treat sleep so frivolously, especially REM sleep, which is most prominent in the early morning hours that we often do not treat ourselves to & often cut-back on in our modern lifestyles.
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