How much sleeps should we get each day?
How is sleep regulated, and what good exactly is it to our mind and learning?
What are sleep “best-practices” ?
This article assembles inputs and blurbs from different places to try and build up wide understanding of the topic of sleep,
Why do we sleep?
This isn’t as easy to answer as you’d expect. There are many theories on why we sleep, some of them relate this to evolutionary needs (energy conservation, enabling inactivity, etc..) or restoration (of what’s lost when awake), etc…
More and more links however are established between ‘brain plasticity’ and sleep. The effect is obvious for infants who sleep up to 14 hrs, half of which is REM (see below). A link is established for adults too, and sleep deprivation is consistently shown to lead to impaired and weakened cognitive functions.
So How much sleep is enough?
While sleep requirements vary slightly from person to person, most healthy adults need between seven and a half to nine hours of sleep per night to function at their best.
Other studies say that 7 hours of sleep is actually better than 8 and more, which is correlated (key word) with health problems and higher mortality rates (See this)
Researchers at the University of California, San Francisco discovered that some people have a gene that enables them to do well on six hours of sleep a night (and sometimes less). This gene, however, is very rare, appearing in less than 3% of the population. For the other 97% of us, six hours doesn’t come close to cutting it.
The Nature of Sleep? Stages ? How?
Sleep is broadly split into two big categories: REM ( Rapid-Eye Movement : Most of the dreaming is done here, brain most active, progressively longer) sleep, when we’re dreaming, and non-REM sleep. Non-REM sleep moves through several, progressively deeper stages:
- Stage I: a light doze, not very restorative (N1)
- Stage II: middle sleep, restorative (N2)
- Stage III: slow-wave deep sleep, the most restorative of all (N3) [[During the deep stages of NREM sleep, the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system.]]
Typical Length of the different Stages of Sleep over a night
(Notice how REM length increases with each subsequent cycle)
How does the body manage sleep?
The Body has two Sleep control components:
- circadian clock – This clock is a biological clock in our body that times different functions of the body. See below for a graph of what activities it can regulate.. the circadian clock produces sleepiness in 24 hour cycles by releasing a hormone (usually after around 15-18 hours from waking up, roughly at 21.00)
- homeostatic control – wake-meter measures the period in which we stay awake and triggers sleepiness after we stay up for long enough
Features of a human 24hr circadian rhythm
Interesting Applications:
Alarms are bad for you:
Getting out of bed can be difficult if your alarm goes off when you’re in the middle of deep sleep (Stage N3). You’d feel best if you wake up at the end of a sleep cycle. Try setting a sleeping time that’s a multiple of 90 minutes, the length of the average sleep cycle –> You will wake up feeling better if you don’t wake up in the middle of deep sleep.
Sleeping and Weight-gain:
Sleep deprivation is correlated with overeating and weight gain.
There are two hormones in your body that regulate feelings of hunger and fullness. Ghrelin stimulates appetite, leptin sends signals to the brain when you are full. With less sleep than needed, ghrelin levels go up, stimulating your appetite so you want more food than normal, and your leptin levels go down, meaning you don’t feel satisfied and want to keep eating. So, the more sleep you lose, the more food your body will crave.
Then and Now
“If you look at the 1960s and 1970s, people reported average sleep times of 8-8.5 hours a night,” an assistant professor in the University of Utah’s division of pulmonary medicine and a sleep medicine specialist says. “Today, it’s much more likely to be 7-7.5 hours or less.”
On Sleeping habits of remarkable People:
The below Infographic was created by RJ Andrews that summarizes sleeping habits of a number of geniuses (and which has gone viral) , inspired by Mason Currey’s (2013) book “Daily Rituals”.. :
Sleeping Habits by RJ Andrews
Not many seem to have ‘weird’ sleeping habits… Many studies seem to point out that you need to sleep ‘as much as the body demands’ because these needs can vary genetically. Better levels of creativity and alertness seem to be correlated with good and long sleeping habits.
Additionally, even though it has become ‘pop’ to speak of Da Vinci’s poliphasic sleeping habits (20 minutes sleep every four hours for a total of 2 hrs of sleep per day), and similar claims for Tesla, Napoleon… It seems that these claims aren’t well substantiated. [ See Here and Here ]
Salvador Dali, and many other creative people, like Edison, were reported to have ‘power naps’ or hypnagogic sleep, wherein the nap includes just the transitional state from wakefulness to sleep. Dali would famously hold a key in his hand, and rest on a sofa with his hand over its arm, and a dish on the ground. As soon as he starts falling asleep the key falls, makes a noise and he wakes up.
Monophasic , Biphasic, of Poliphasic Sleep??
(see below for a representation of different sleep patterns)
It also seems that biphasic sleep is very natural for humans, considering that our homeostatic cycle seems to ‘demand’ sleep after around 7-8 hours from waking up (the siesta) [[ Read more on that Here ]]
Although poliphasic sleep is hyped, a critique of Uberman sleep, and other types of poliphasic sleep, [ A sleep where a person sleeps many ‘short’ times over the course of a day; See here ] is that the result could be reduced mental strength and power, loss of concentration.. Additionally they are very hard to maintain. Scientifically, a poliphasic sleep has been proven to be better than an equivalent sleep for sleep deprived individuals, but not compared to the general (This means that using poliphasic sleep to sleep 3 hours over a day is better than sleeping 3 hours at once ,, but poliphasically sleeping 3 hours isn’t better than regular sleep).
So for now, Monophasic, or Biphasic sleep (7 or 8 hours) seems to be the best choice !
Sleep patterns for different sleeping styles, the darker color represents sleep:
Refs:
http://www.helpguide.org/articles/sleep/how-much-sleep-do-you-need.htm#hours
http://www.webmd.com/sleep-disorders/features/adult-sleep-needs-and-habits
http://online.wsj.com/articles/sleep-experts-close-in-on-the-optimal-nights-sleep-1405984970
http://www.supermemo.com/
https://www.freelancersunion.org/blog/2014/08/04/strange-sleep-6-brilliant-people/