Our body needs adequate rest according to the biological clock.  So, the question is, “how do we get a quality sleep and wake up feeling rejuvenated?”

There are 2 factors that we need to consider:

1. Hours of Sleep.  The ideal sleep duration is 7 – 8 hours.  However, the amount of sleep depends on age also.   Children require 11 – 13 hours, whereas adults 7 – 8.
2. Quality of Sleep. The stages of sleep are light sleep, deep sleep, and dreaming (REM).  The cycle of each one should be completely achieved, as the stages are all interrelated.

3 Cycles of Sleep

Normally, the sleep cycle lasts between 30 seconds and 7 minutes.  It is a transitional stage in which even the least stimulation causes you to wake up. Then, it progresses to other stages.

• Light Sleep is the first stage of sleep but without dreams.
• Deep Sleep is the stage when your body enters relaxation mode which lasts 30 – 60 minutes. During this time, body temperature and blood pressure will drop, and heart rate lowers to approximately 60 beats per minute. Growth hormone is secreted during this stage. 
• Dream or REM Sleep is another important cycle of sleep, during which the body is relaxed but your brain is still awake.  In addition, dreaming helps improve memories about our various skills.  Thus, in order to have good sleep, you need both quantity and quality of sleep. Some people wake up feeling refreshed after only 4 or 5 hours of sleep, but it may be just light sleep as it can make you feel rejuvenated.  So, we need to consider other factors also.  For example, if you feel invigorated but your cognitive abilities decrease, it may be that you have inadequate hours of sleep and will need more to improve the percentage of each cycle.

Others may sleep for more than 7 – 8 hours but do not wake up feeling refreshed.  It is possible that, though the amount of sleep is sufficient, the quality of sleep is not.  This means they reach only light sleep stage but do not progrees into deep sleep stage, and they will have to find out why this is the case.

Silent Danger of Sleep and Wake Cycle 

Some people only sleep for a few hours but they achieve quality of sleep.  This could be related to the body’s internal processes, genetics, and adaptability.

Others may sleep for long periods of time, but wake up feeling dull.  This is because they are in a sleep and wake cycle that makes respiratory system and blood vessels work harder.  That is why they wake up feeling tired instead of refreshed.

Nowadays, there is an increasing number of patients who discover their sleep disorder during a regular checkup.  The condition is considered a silent threat that raises the risk of a number of other illnesses, including diabetes, hypertension, ischemic stroke, and coronary artery disease.

Common symptoms that may occur due to insufficient sleep include drowsiness and daytime tiredness, declined thinking capability and memory capacity loss, cognitive deterioration, forgetfulness, sleep and wake cycle, sleep apnea (snores are punctuated by pauses in breathing).  These will require proper diagnoses in order to determine the root cause.

For the above reasons, achieving 7 or 8 hours of sleep every night may not mean adequate quality sleep.  For your body and brain to be properly rested, you have to take into account the depth of your sleep.  It is also crucial to maintain the schedule of when to go to bed and to wake up, neither of which should be too late.

Can A Lot of Sleep Make Up for A Lack of Sleep?

Sufficient number of sleeping hours for working people is about 7 – 8.  If you sleep longer than that, you will not be able to sleep deeply; as your body recognizes that the number of hours for sleeping has now been reached.  You will fall into sleep and wake cycle during which you cannot sleep soundly the way you do at the beginning, because your body has already restored enough energy.  This is analogous to your mobile phone: it should not be left charging all night.  Similarly, with too much sleep, your body will become lethargic instead of feeling rejuvenated.

In the case that you can only sleep less than 4 hours.  This is considered a “sleep deprived” situation.  If it occurs on 3 consecutive nights, then on the 4^th night – if you manage to fall asleep and regardless of how many hours it may be – your body will compensate by skipping to deep sleep stage as soon as you fall asleep.  This is in contrast to the normal process when it usually takes 30 – 60 minutes, as your body achieves light sleep and gradually transitions to later stages.  If you have enough time, your body will begin to re-adjust your sleep cycle again.

However, if you still need to wake up within 4 hours, the next time you fall asleep you will achieve deep sleep for short periods; as your body has not completed the required full sleep cycle. You may wake up and feel renewed, but your memory may not be so effective as before.

Therefore, when possible, after 3 nights of sleep deprivation, you should find an opportunity to obtain sufficient rejuvenating or compensating sleep that is appropriate for you.  This will allow your body to refresh and return to its proper condition within a few days – or one, if you can manage an adequate sleep.

In any case, this will depend on your age also; as the brain capabilities differ accordingly.  The renewal is faster in younger people, while it takes longer for older adults.  Thus, there is no established formula for compensating sleeps.  It is up to each person’s condition to dictate how much the body will be able to regenerate.