I've read a book called Sleep Thieves. Good book.

Simple answer. The human body needs sleep.

If your body is deprived of too much sleep you can expirience whats called Micro Sleep. For a few seconds parts of your brain will shut down. This can happen while your driving or flying.

Sleep deprivation causes stress on the human body. which can lead to a whole world of truble. Check out Stress: Signs, Symptoms, Causes, and Effects

Intellectual signs

Memory problems.
Difficulty making decisions.
Inability to concentrate.
Confusion.
Seeing only the negative.
Repetitive or racing thoughts.
Poor judgment.
Loss of objectivity.
Desire to escape or run away

Emotional signs

Moody and hypersensitive.
Restlessness and anxiety.
Depression.
Anger and resentment.
Easily irritated and ??on edge?.
Sense of being overwhelmed.
Lack of confidence.
Apathy.
Urge to laugh or cry at inappropriate times.

Physical

Headaches.
Digestive problems.
Muscle tension and pain.
Sleep disturbances.
Fatigue.
Chest pain, irregular heartbeat.
High blood pressure.
Weight gain or loss.
Asthma or shortness of breath.
Skin problems.
Decreased sex drive.

Behavioral symptoms

Eating more or less.
Sleeping too much or too little.
Isolating yourself from others.
Neglecting your responsibilities.
Increasing alcohol and drug use.
Nervous habits (e.g. nail biting, pacing).
Teeth grinding or jaw clenching.
Overdoing activities such as exercising or shopping.
Losing your temper.
Overreacting to unexpected problems.


Deprive yourself of sleep for 40-60 hours and you start to hallucinate. Keep on going and you become more useless then a Drunk.

People have locked themselves in chambers for weeks to see how long the body would sleep if unaffected by alarms or work. About 9 hours of sleep is ideal. I would suggest no less then 8 on an average basis since the sleep cycle is 4 hours. Try an expirament. Sleep for 7 hours and wake up. see how you feel. Then the next day sleep 8. You will probably feel better since your sleep cycle was able to complete itself. Keep in mind the most restfull sleep is REM which is in the last stage of the sleep cycle.