Sleep is an essential ingredient for our well-being, and it manifests both externally and internally. Work it out for yourself.....the normal human being is supposed to spend about one third of his/her life in sleep. Why would nature have programmed these rest periods as being absolutely necessary for our bodies? In fact, cell regeneration and cell growth are known to occur only during periods of rest, and many hormones essential to proper functioning of the human body are produced only when the body is at its deepest sleep stage.

Have you noticed how your entire facial structure changes after a night of undisturbed, relaxed sleep? Hollows under the eyes plump up, ravines flanking your nose turn into manageable furrows, the eyes sparkle, the eye-whites become, well 'white'. instead of off-white or pink.

What is sleep? Let's first understand the process of sleep, before examining how sleep changes with age, and what you can do to ensure that you get enough of this natural panacea for all problems. When someone asks you to 'sleep on it', you are getting good advice, because your subconscious mind gets to work on the problem overnight.

Scientists have used the following behavioral criteria in an attempt to define sleep in universally accepted terms:

There are 2 basic stages in the sleep process. REM (Rapid Eye Movement) sleep and NREM (non-REM) sleep. NREM sleep is divided further into four sleep stages, numbered 1, 2, 3 and 4. Normal sleep begins with stage 1 and progresses into 2, 3 and 4, getting more and more deep with each stage. The deeper sleep is achieved at stages 3 and 4. (This is also the stage during which HGH and melatonin is released by the pineal gland). The fifth stage, which is actually lighter, is REM sleep, during which dreaming occurs.
The different sleep stages are also referred to as S-sleep (synchronized EEG pattern sleep) and D-sleep (desynchronized EEG pattern sleep). D-sleep is the same as REM or dream sleep; S-sleep is another name for NREM, ( also known as orthodox or quiet sleep).

The five stages of sleep:

Stage 1: As we fall asleep, we enter the transition state called stage 1 and begin our first "sleep cycle". This very light sleep stage usually lasts 2-5 minutes. If sleep remains undisturbed it will progress to stage 2 sleep. Stage 1 contributes 2-5 % of normal sleep, (but increases hugely in cases of insomnia and disorders that produce frequent arousals such as apnea) .

Stage 2: This is a much deeper sleep than stage 1. The brain waves go into theta mode, and lead into stages 3 and 4 in around 10-20 minutes. Stage 2 sleep occupies approximately 50-65% of our sleep time, lasting 15-30 minutes in each cycle.. During the latter part of the night we spend more and more time alternating between stages 2 & REM sleep.

Stage 4: The deepest sleep of all, during which a sleeping person is 'dead to the world'. Blood pressure and heart rate fluctuate and the sleeper's brain heats up. Delta sleep is characterized by very high voltage slow brain waves. It is similar to being in a coma, but unlike a coma, it's reversible. As we transverse these first four stages of sleep our respiration and heart rate slow and the body is almost immobile.

Stage 5: REM (rapid eye movement). All of a sudden, after 20-30 minutes of slow wave sleep, we transfer back into stage 2, and almost immediately change gears into very active brain wave pattern known as REM sleep. Simultaneous with this transfer into REM, our respiration and heart rate increases substantially and we lose our ability to use our postural or skeletal muscles.
The first REM period lasts only about ten minutes. After that, the sleeper goes back into a deep stage 4 sleep. Again, the sleeper returns into a REM stage after a short period, and cycles through REM and stage 4 continue until the sleeper awakens. Along with this, our brain becomes so activated that we start to hallucinate and dream. Our eyes move as in wakefulness, and in relation to what we are dreaming. In effect, we are, at this stage ,a highly activated brain in a paralyzed body. This paradoxical state will last 10-20 minutes and then we "fall" back down into stage 2 again.

This is the end of a sleep cycle and then it all starts over again, As the night progresses we gradually lose our delta sleep, and replace it with longer and longer periods of alternating stage 2 and REM sleep. By the final sleep cycle of the night, we spend approximately half our sleep time in stage 2 and half in REM.

NREM and REM states occur in a roughly 90 minute cycles, which is repeated 5 to 6 times a night. In most adults Stages 3 and 4, or Delta sleep, are completed within the first two 90 minute sleep cycles, or within the first three hours of sleep. Contrary to popular belief, it is delta sleep that is the "deepest" stage of sleep (not REM) and the most restorative. It is delta sleep that a sleep deprived person's brain craves the first and foremost. In children, delta sleep can occupy up to 40% of all sleep time.

During the day while we are awake, our normal brain wave pattern is mainly in a high-frequency beta pattern. When we fall asleep, our brain-wave patterns slow down changing first from beta into alpha (pre-sleep drowsiness), and then into a back-and-forth cycle through REM sleep followed by NREM sleep. Stage 2 & REM sleep takes place in a theta brain-wave pattern, while non-REM sleep stages 3 & 4 happens in the slower delta pattern, which occur during the first part of the sleep cycle.

Sleep Apnea & Sleep Disorders

Sleep & Aging