How Do We Fall Asleep?

Do you know how do we fall asleep? We fall asleep because we have reached that time of the twenty-four hours when we have learned to fall asleep. Many other things can, however, contribute to the ease with which we fall asleep.

For example, if it is a long time since you last slept, you’ll fall asleep more quickly. People who leave been without sleep for two whole days and nights can drop off in a few seconds and at any time of the clock. Monotony, warmth, confinement, and the satisfaction of needs, will all make us more likely to drop off. Let’s know more about how do we fall asleep?

Our biological clock

We see patients who say they just cannot get to sleep at night and that, as a consequence, they are so tired that they feel unable to get up early in the morning. They might be surprised to find that there is a way to get up earlier.

If those same people flew to India from London they would have to make a five-hour change to their watches, and within a couple of weeks would largely have adjusted to the local time and conditions, and be getting up five hours earlier than they had been at home and falling asleep five hours earlier.

On the first few nights in India, however, they would find it difficult to fall asleep at the local bedtime and be very sleepy when it was time to get up in the morning.

By day they would be less efficient than at home and have less of a sense of well-being. The usual rhythms of their appetite for food and of their bowel movements, and, if measured, the usual daily rise and fall of body temperature across the twenty-four hours, would all be initially out of step with local time.

How do we fall asleep?

The social pressure weighing on them to get up earlier in India would gradually lead them to be able to fall asleep earlier and, certainly, with the passage of even more weeks, their whole bodily and mental systems would adjust to the new time clock.

They might still have the same trouble getting up early in India as they did in London, but they would find that they could indeed fall asleep earlier as a routine, provided they have also made a habit of getting up earlier.

The twenty-four-hour rhythm

We all have within us a biological clock, or biorhythm, which works on an approximate twenty-four-hour cycle. It is called the circadian rhythm, deriving from the Latin circa Diem, meaning about a day.

In normal life, we are not much aware of it, but if we fly to the other side of the world we realize its importance and in fact, it takes a couple of months for the bodily systems to fully adjust.

The very simplest forms of life, animal or vegetable, have these circadian rhythms of approximately twenty-four hours and if even normal blood and nerve supply, then provided they receive sufficient nutrients, they will go on living and showing a circadian rhythm in the amount of oxygen they use or nutrients they take in.

In the animal as a whole, the rhythmic orchestra of the tissues has a conductor, a con-coordinating center that keeps all the body rhythms in step.

It does so by means of nervous and chemical messages and is located in a small part of the brain called the suprachiasmatic nucleus. In very primitive animals this part is right up at the front end of the brain where it is most exposed to light and dark.

Across the day and night as a whole these two balance out, but during wakeful activity the processes of breakdown out-weigh those of renewal, and during rest the processes of renewal catch up and overtake the breakdown.

For simple forms of early animal life the daylight hours meant greater warmth and consequently more movement, both for finding food and for getting into a position to be eaten, and, with the development of vision, a  greater capacity for finding food.

The dark phase of the twenty-four hours is, correspondingly, a cold time, a time of reduced activity, and a time for digestion of the food that has been eaten and its use for the renewal of the whole organism.

It seems that over many hundreds of millions of years the capacity for changing the body’s inner arrangements, according to a rhythm that approximates to the time needed for the earth to rotate on its axis the time for changing form light and warmth to cold and darkness has become built into the genetic constitution of every living creature.

As animals evolved, some, such as the ancestors of opossums, became warm-blooded and then more specialized, so that they took advantage of the relative immobility of other creatures during the dark phase and became nocturnal feeders, as is the case with most rodents and the owls that feed in turn upon them.

Body temperature

The circadian rhythm can very easily be demonstrated by taking someone’s temperature every hour. The temperature will rise during the day and probably reach a peak during the afternoon or evening and it will decline during sleep, to reach its lowest level in the early hours of the morning.

If you stay awake all night your temperature will still fall, though it will not fall as low as it would have done had you slept. Likewise, if you continue to lie in bed all day your temperature will inevitably rise, though not to such heights as it would have done had you been physically active.

Our capacities for intellectual and bodily skill rise and fall with our temperature, as does the urge to be on the move. If you have to make arithmetical calculations or watch a factory production-line for faulty products, you will perform your job better by day when your temperature is higher, and even though awake, you will do less well at night if your temperature has fallen.

Temperature and mental and physical performance are tied very closely together, as the diagram on the previous page illustrates.

What makes you sleep

This graph shows both the rhythmic daily rise and fall of body temperature and the link between body temperature and our physical and mental abilities.


Among the other functions tied to the circadian rhythm is the feeling of sleepiness and the readiness to fall asleep. Even while being kept without sleep for several days and nights, people are more alert and lively during the tie of the twenty-four hours when they are accustomed to being awake, and it is during the time when they customarily sleep that there is the greatest difficulty in staying awake.

Keep the clock regular

People who do not stick to a regular time for going to bed and for getting up, do not have such a sharply defined rise and fall in body temperature, or rise and fall of their tendency to be sleepy.

In one American study by Dr. John Taub in Charlottesville, Virginia, a group of young adults, who customarily led a life in which there was a variation of three or four hours from night tonight in the time when they chose to go to bed, as compared with another group who were of the day the regular people had faster reaction times and felt themselves to be happier than those who were irregular in their sleeping habits.

Not only did the regular people feel themselves to be happier, but they also had a higher opinion of the quality of their sleep and felt that they also had a higher opinion of the quality of their sleep and felt that they had more energy by day.

It may be that some of us have a constitution that makes us into people who just don’t keep regular hours and that the same basic constitution is one that makes us feel less happy and less energetic and to have a sense of poor sleep.

However, it seems a reasonable guess that the irregular hours of sleep were partly a cause of feeling both less well and less pleased with life.

Certainly, if irregular hours are forced on people, through shift-work, for example, many will feel that as a consequence of the irregularity of hours they are less happy, and have less energy and a poorer quality of sleep.

The same research workers in the United States did other studies using volunteers whose sleep patterns were altered.

Either they were deliberately allowed to sleep three hours longer in the morning, or to go to bed three hours later and then sleep three hours later, or were put to bed three hours earlier and woken up three hours earlier.

All such deliberate interference with the normal hours of going to sleep and waking up caused the volunteers to become slightly less efficient by day and to have less of a sense of well-being.

They were at their best when they followed their normal, regular pattern of going to sleep and waking up.

That’s why, if you have been sleeping badly and are feeling tired and low throughout the day you should strengthen your biological clock so that it will help you to drop off quickly to sleep at night and enable you to be really efficient by the day.

Sharpen it up by always going to bed at about the same time each night and always getting up at the same time in the morning.

Why you should get up early

The time you get up in the morning governs the time you will be feeling tired at night. So if you want to fall asleep more readily at night, then get up earlier in the morning! And do so regularly. You will get sleep of better quality and feel happier and more energetic by day if you keep it all regular.

Sixteen-year-old schoolboy Andrew Miles was sent to us for help because he couldn’t fall asleep until 2 am. He was at a boarding school where lessons did not begin until about 10 am, so he never got up until 9.30 am.

When he came to us we got him up regularly at 7 am each day and within a couple of weeks, he has been regularly fast asleep by 11 pm. It had been the routine at his school at a more reasonable hour each evening.

Nobody would have thought him in any way peculiar and they would never have been sent to see us. It was just a matter of adjusting his circadian rhythm to a more acceptable cycle.

Different rhythms of waking and sleeping for different people

The term circadian rhythm means, as we have said, a rhythm of approximately twenty-four hours, but everybody is different and the innate rhythm is not precisely twenty-four hours for everybody. In most people, it lasts slightly longer and in only a few as little as twenty-four hours.

You may have read accounts of people who go into underground caves and stay there for many weeks at a time for the purposes of scientific experiments.

They leave they’re watching behind at the surface and, in total darkness, and devoid of an external cause, they begin to free run, as it is called.

Under these circumstances, many of them will start to live a 25-hour life cycle, or even a 48-50-hour cycle and only a few will adopt a rhythm around 24 hours.

In normal life our rhythms are constantly being reset to then twenty-four hours by external factors (termed zeitgebers by specialists); especially by social activity, by the morning alarm clock and getting up, by the times of meals and the alternation of light and dark.

In many lower animals, such as rats, light and dark are the key factors, but in human beings as a social activity seems much more important.

How Do We Fall Asleep

Your body’s rhythms for going to sleep and waking up are continually being adjusted by external factors such as the morning alarm clock.

Nevertheless, there is a greater tendency for blind people to free run on, say, a twenty-five-hour inner clock during their ordinary lives; and there are people who do not conform to society’s conventions who do not have regular work and do not care if it is night or day-who in their lives seem liable to free run.

People who free run on a twenty-five-hour rhythm will get up an hour later each day and likewise will, day by day, fall asleep one hour later and wake up an hour later and another hour later until they are not sleeping at all during conventional hours, but sleep during the day.

Days later they will again start to become sleepy in the evenings and wakeful in the mornings. This cycle will continue so that they get into step with the rest of their countrymen and out of step, into step and out of step again about every twenty-five days.

what-makes-you-sleep 2

A few people need just six hours of sleep each night, a few sleep for nine hours, but most have around seven to eight hours of sleep.

It is because we are all sensitive to a different degree to the external factors-the zeitgebers that influence our waking and sleeping habits and because we all differ in ore tendency to free run that we also differ in how easy it is to feel wakeful and alert at a precise and regular morning hour.

In fact, in any human activity, or anything else in the world of biology, it is important to remember the wide individual variations.

Some people have big feet and some have small feet: but most peoples are in the middle. Some people sleep for a long time and others for a short time: most people are in finding it difficult: again most people are in the middle.

As a general rule, though, if you stick firmly to regular hours you can help your own inner clock to keep regular habits. 

What else makes us sleep?

Lack of sleep

Everyone knows that if you have little sleep one night, then the following day you are more likely to drop off in the afternoon or early in the evening.

In the early 1970s, two American psychologists in Gainesville, Florida, measured the time taken between settling to sleep and actually dropping off and showed that it did indeed get volunteers last slept.

It means that if you are very short of sleep you would be unwise to take on tasks such as prolonged driving on motorways and freeways where you might fall asleep without warning and have an accident.

Monotony and other causes

Motorway and freeway driving is a well-known cause of sleepiness and it’s the monotony that’s the principal reason.

A few years ago a British motoring magazine published a discussion about falling asleep when driving, together with the results of a survey by the police in the country of Cambria, in the north of England. The M6 motorway runs from London, northwards through the industrial regions of the Midlands and Lancashire, and they continue through the beautiful stretches of the Cambrian country side.

The route through the industrial areas is always busy, with cars and trucks moving in and out so that there is always plenty to keep drivers awake.

In Cumbrian, there are long empty stretches where a driver might scarcely see another vehicle, and monotony and the tiredness caused by a long journey can often become overwhelming.

The Cambrian police found that around 25 percent of accidents seemed to have been caused by motorists falling asleep at the wheel and simply driving off the road at a shallow angle, without leaving any tire marks on the road surface.

You can understand the effects of monotony more easily if you consider how anything new or exciting alerts you and prevents you from falling asleep.

The novelty will keep you awake, and by contrast, the uniformity that monotony imposes will predispose you to sleep.

We have demonstrated this in our laboratory by comparing the liability to fall asleep of volunteers who simply lie in bed doing nothing in particular, with the liability of others who are deliberately subjected to monotonous hooting noises.

We found that the monotonous noises made people fall asleep more quickly, and this explains the use of rhythmic sounds such as the noise of waves on the seashore or noises like heartbeats to help people who feel they have difficulty in getting to sleep at night.

Knowing that monotony brings sleep more quickly is useful to parents of wakeful young babies. If, once you have attended to all you healthy baby’s basic needs-feeding, a clean nappy or diaper, and warmth and you still have trouble getting him or her off to the trick. And many parents find playing monotonous music or singing repetitive lullabies have the same effect.

How do we fall asleep

Rocking a baby is a good example of how rhythmic monotony tends to bring on sleep.

Obviously, when you are walking about, you are less likely to fall asleep than when sitting still. Immobility and confinement in a small car, for example, or in the cabin of a truck on a highway, again contribute to the tendency to fall asleep.

The same is true of warmth. If you feel cold, your muscles become tenser and you may even shiver, all of which is a mechanism for maintaining your best temperature but it tends at the same time to keep you awake.

When you feel, warm your muscles relax and sleep comes more easily; a good reason to make sure your bedroom is warm and that you have sufficient bedclothes during the cold winter months.

The satisfaction of important needs is also followed by relaxation and a greater tendency to sleepiness. Many of us will fall asleep more readily after a rood meal or sexual intercourse.

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