Our sleep requirement changes throughout the different stages of our life, depending on our physical and mental health, lifestyle and work pressure.Today, we are constantly being stimulated with technology and various modes of entertainment, in addition to juggling the unceasing pressures of work and home. Everybody seems to need more than 24 hours in a day to carry out all their activities. Shortage of time has become a mass epidemic affecting all sections of society—school-going children, college students, working professionals and stay-at-home mothers.

So where can we get hold of extra time?

Since we can’t ‘buy’ time, we tend cut down spending hours on those activities we deem ‘unnecessary’. For most people, this unnecessary activity happens to be—you guessed it—sleep. Devoting a quarter of our 24 hours every day has become too precious for most of us. So we end up compromising our slumber.

However, let us imagine the ideal scenario where we have enough time in our lives to do all the activities we want. The question that arises then is, “How many hours should we sleep?”

Optimal sleep duration experiment

A study was conducted to find out the answer to this commonly-asked question. Simulating the lifestyle of ancient cavemen, volunteers entered a sleep lab every evening by 6 pm and left the lab by sunrise. The inside of the lab had been darkened completely and made sound-proof. The volunteers’ sleep was monitored and their eye movements were recorded to measure how much time they slept and the quality of their sleep. Also, there were no other activities that the volunteers could indulge in.

The result

Initially, to recover their accumulated ‘sleep debt’, they did sleep for 10 – 12 hours; but the following nights all of them slept for an average of seven hours and 45 minutes with a variation range of seven to eight hours. Surprisingly, the volunteers were in a happy state of mind during the entire experiment.

Across cultures and geographic regions the sleep hours are fairly similar, averaging about seven to eight hours. And this holds true even for the Norwegians living in the Arctic Circle where they experience extended durations of daylight and
night-time.

The affect of mental and physical health on our sleep

Our sleep duration also varies according to our health status. For example, a person with a mental illness such as schizophrenia has a reversed cycle of sleep and wakefulness, with the person sleeping only during the daytime. A person with hypothyroidism has an enhanced sleep requirement; such a person is inclined to sleep at anytime, even if they’ve had a restful sleep of eight hours at night.

How to measure your sleep debt

Sleep debt is related to ‘sleep latency’—which is the stretch of time between going to bed and falling asleep. This implies that the more sleep debt you accumulate over the week, the less time you will need to fall asleep. It is a simple test you can perform—just lie down and close your eyes for 20 minutes. If you don’t fall asleep during these 20 minutes, then your sleep debt is zero. This indicates that you have been sleeping enough. Note: this test of sleep debt presupposes that your inability to sleep is not due to pain or illness.

There is also a downside of having zero sleep debt, because it signifies that you will have a hard time in falling asleep. In other words, you need to build up some sleep debt, it should be just enough to be able to initiate sleep within a reasonable time-frame and maintain a moderate range of  ‘sleep latency’.

Restoring the sleep debt

Most people would have built up a sleep debt, either by studying through the night,  working long hours or by various other ways.

Does that then mean that once we start a sleep debt, we go on accruing it? No, you can restore your sleep debt accumulated during the week. This is done with planned naps. You should make the time to sit or lie down quietly for 20 minutes or more, two to three times during the day.

What is important in this ‘pay back’ of sleep debt is the duration of your naps. It must consist of several minutes; not the catnaps of one or two minutes that you get in a meeting, conference or lecture hall because of your high sleep debt. This method of renewing your sleep debt was proved in an extreme experiment.

Sleep ‘pay back’ experiment

The volunteers in this experiment were awakened every minute during their regular night sleep. They did fall back to sleep immediately within 10 – 15 seconds and they completed their eight hours of sleep. However, because of the repeated interruptions, the volunteers were sleepy and irritable the next day.

They tried to offset these symptoms by having short naps of 10 – 15 minutes. But towards the end of the day a new debt accrued and the sleep debt symptoms showed more intensely. This experiment shows that our ‘sleep bank’ doesn’t accept small piecemeal credits. We need sustained sleep of at least 20 minutes to partially offset our sleep debt.

Can you make up for lost sleep on the weekend?

Suppose you can afford only six hours of daily sleep during your working five-day week; you are therefore carrying a sleep debt of 10 hours during the week, given that you need eight hours of sleep every night. Thus, every night through the working week you continue to incur two hours of sleep debt. However, sleeping late on weekends and holidays will not help, because you have to balance your sleep debit with a credit of 10 hours of sleep. Also, this effect or recovery will be transient because your body clock will not allow you to sleep for long; your body will stop secreting the sleep hormone melatonin. And new sleep debt will begin to accumulate.

What is the way out then?

My solution to this problem of continually accumulating sleep debt is to have a regular sleep of about seven-and-half hours at night, followed by two or three bouts of 20-minute naps during the day. In this way, you can even anticipate a sleep debt coming your way.

If you have an upcoming party or conference call that you have to attend late at night, you can take preventative naps. But it is important to not make it a habit or you will end up with ‘sleep reversal’. You will find yourself dozing off in the daytime or going about your work in a drowsy state because of your reversed mind/body circadian rhythm.

So take care of your sleep debt and stay alert and happy.

Symptoms of sleep debt

  • Drowsiness and laziness during daytime
  • Fatigue
  • Irritability
  • Vague body aches
  • Decreased or absent sex drive
  • Brain fog and lack of focus
  • Accident prone
  • Lack of initiative
  • Habitual procrastination
  • Low energy

The sleep debt reference values

This is the time it takes you to fall asleep and how that corelates to your sleep debt:
0 to 5 minutes: High sleep debt—you are in danger and may be prone to accidents and illnesses
5 to 10 minutes: Borderline
10 to 15 minutes: Manageable sleep load
15 to 20 minutes: Full alertness

This was first published in the August 2014 issue of Complete Wellbeing.

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