Perhaps the most necessary component of our everyday lives – but the least understood – is the phenomenon of sleep.
Though it’s still quite a mysterious process, we do know an increasing amount about sleep.
So let’s start at the beginning: what exactly is its purpose?
Sleep was once considered an extended state of rest, where the brain powered down to allow the body to rest. It was very much viewed as a ‘recharge,’ a state where the body’s extraneous functions were switched off.
Scientists now know that nothing could be further from the truth.
Sleep is actually a complex and active second state, with cycles and body and brain movements.
The necessity of sleep has not been exactly pinpointed, but researchers believe that there are several different variables that contribute to humans’ sleep requirement.
Some believe that since our core temperature drops during sleep, the primary cause of a night’s rest may be simple energy conservation.
This has been disputed, as humans have evolved to sleep for long periods of time, rather than in short bursts, which is all that would be needed to simply ‘conserve energy.’
Other theories prevail.
The most accepted understanding of sleep today is that it is a time of organization, processing, and physical restoration. For example, the human brain may use sleep to organize and process new information and intel supported by long-term memory.
Sleep is also thought to aid in the renewal of the body’s tissues and nerve cells, leading to cellular restoration. This has been proven by the body’s ability to heal physical wounds faster and boost immunity when faced with a good night’s rest.
There is even a tangible difference in growth hormone presence when test animals are subjected to variable amounts of sleep – those who sleep less have less growth hormone, and vice versa.
In other words, rest does heal. It is also important to note that in young children and babies, sleep helps expedite brain development, function and connections.
In young children and even adults, sleep has been found to hasten and strengthen decision making and reasoning skills and assist in strengthening memory and facilitating next day learning.
Our Ancestors Didn’t Sleep Like This
Many have tried to challenge the traditional sleeping pattern, which is divided into a chunk of ‘awake’ time and a chunk of ‘sleep’ time.
DaVinci was said to sleep for 30 minutes at a time every 6 hours to maximize his productivity, and a few brave (and busy) folks today have experimented with polyphasic sleep, which refers to having multiple sleeping periods over the course of a 24 hour day.
But monophasic sleep (sleeping for one period during the day) is widely established and has its merits.
How did we come to sleep like this?
Convenience is one reason. Sleeping at night when it is dark is simply more practical than sleeping during the day, as most of our activities take place then. In addition, the brain starts to produce a chemical, melatonin, as the light fades to night. This chemical makes you tired, signaling that it is time to go to bed.
Interestingly, research shows that monophasic sleep may not always have been the norm.
Research of the 16th century indicates that communities may have had two distinct sleep periods during a single night- a “first sleep” of four hours, a break of about one or two hours and then a “second sleep” of about four more hours.
In these days, it was a common and recognized pattern, with doctor’s manuals indicating what to do during a “first sleep” or “second sleep.”
People also utilized their sleep break by completing work, visiting neighbors, smoking, reading, chatting or having sex.
Interestingly, this phenomenon largely disappeared in the next century due to increase in urban progress.
As technology became more available, nighttime activity increased. Consider the effect of the creation of electric lights, the new availability of night activities in urban areas and the choice to be more productive at night.
The time of rest was sizably shortened by this boom in productivity and activity, negating the need for an hour long rest between sleep cycles. There simply wasn’t enough time!
This transition happened quite a while ago, but when some find themselves waking in the middle of the night their doctors remain unconcerned, convinced that their bodies are simply reverting back to pre-industrial ancestral patterns.
To Siesta Or Not – The Cultural Question
While our ancestors certainly slept differently, cultures around the world have different sleep patterns as well.
One of the determining factors of how often and when we sleep is increasingly the use of artificial light from the lights in our room to the use of glowing electronic devices.
Interestingly, sleep time differs enormously in cultures around the world. Some countries take naps (Spain, Argentina) while some wouldn’t dream of an afternoon siesta (Japan).
Some countries claim higher rates of insomnia than others (Belgium). Some countries like South Africa and Portugal have higher rates of sleep aid use than others.
Children’s sleep is also culturally predetermined, with babies’ sleep varying anywhere from three hours in the countries of New Zealand and Japan to 4-6 hours at a time in the UK and US.
Mid-day rest (naps, siestas) are culturally determined and are ubiquitous in Mediterranean countries, though also practiced in countries like China and Africa where it is permitted at professional places.
In ‘high hustle’ countries, like Japan, naps are, again, seen as counterproductive and thus discouraged. It is no surprise that the amount of time the average Japanese sleeps per night is severely below the global average, coming in at about 6 hours and 50 minutes. It is also little surprise that the Japanese consistently report sleep deprivation.
The Different Stages of Sleep
Now that we know why we sleep, how we have traditionally slept and how sleep is often culturally determined, it’s important to realize that there are many different parts of the sleep cycle.
Sleep activity boils down to brain waves.
Large brainwaves are called beta waves and are present during the day, when the person is active and awake. They are high in frequency. As the person relaxes, the beta waves become alpha waves, which are slower, higher amplitude and more synchronous.
During stage one (N1of the sleep cycle, sleep follows relaxation and brain waves are mixed-frequency as the body begins to slow down. This represents the ‘light’ stage of sleep.
Physically, eye movements slow as the person drifts off. Muscles may also contract suddenly, making the sleeper feel like she/he is falling. This stage only lasts a maximum of about 7 minutes.
Stage two of sleep (N2) is about 10-25 minutes long and eye movement slows to a complete halt. Brain waves are extremely slow, but there is the occasional rapid burst of waves.
By stage three (N3), delta waves (highest in amplitude and slowest in speed) occur alongside of waves of shorter and faster frequency. This is the beginning of deep sleep.
Stage four (N4) represents the deepest sleep of the night, where breathing slows, muscles relax, blood pressure drops, hormones (HGH) are released and cells regenerate. This is certainly the most restorative stage of sleep for the body and mind.
REM sleep follows (often cited as a fifth stage) and is characterized by rapid eye movements and a partial paralysis of skeletal muscles because the REM phase is characterized by the combination of alpha and beta waves, which contribute to dream-like states. Physical effects include increased heart rate, blood pressure, and a loss of temperature regulation.
A sleep cycle is about 90 minutes in total, and the sleeper goes from stage 1 to 4 until complete, then it restarts with REM replacing stage 1. As the sleep progresses, the REM periods of sleep lengthen in time to replace the periods of delta sleep.
Poor Sleep, Poor Health
One of the most aggravating phenomenon is not being able to sleep – a condition characterized as insomnia, which affects over 60 million Americans alone, though no numbers have been determined for the global population.
Even sleep deprivation, a less extreme form of insomnia, has its intense health risks
Sleep deprivation can cause accidents during the day, like car crashes and industrial incidents as sleep deprived workers and drivers struggle to perform routine tasks.
It can dampen cognitive abilities and processes, making it difficult to focus and learn. This holds true especially for children, who face significant challenges in school when deprived of sleep.
Since sleep plays a large role in cementing long-term memory, those who suffer from sleep deprivation may also find that their memory is not as sharp.
Lack of sleep can also lead to serious and chronic health issues, like heart disease, heart failure, blood pressure, stroke, diabetes, heart attack, and irregular heartbeat.
Decreased sex drive is also a side effect due to sleep’s role in producing essential hormones. Lack of sleep can also highly influence depression and anxiety, worsening the symptoms and causing the sufferer greater discomfort.
Physically, a lack of sleep can result in dull skin and eyes, and in puffiness and fine lines because the body releases more of the stress hormone, cortisol, in response to sleep deprivation. Cortisol breaks down collagen, which maintains skin’s elasticity.
Sleep’s relation to body weight is also indisputable. Sleep increases the production of leptin, a hormone that signals satiety to the brain and helps us stop eating. Conversely, sleep deprivation increases the hormone, ghrelin, which stimulates hunger.
As we learned before, sleep is also a major factor in human growth hormone production and too little sleep can diminish that, slowing growth in children and weakening muscle, bones and skin in older age.
Finally, the amount of sleep we get influences our judgement and seriously impacts our ability to function. In essence, sleep is the cornerstone of a healthy and happy life.