Why the body needs sleep

The body demands we sleep a certain amount of time - seven to eight hours for most adults, although some need only five hours, or up to 10. Children need more sleep, which coincides with the release of growth hormones.

Animal studies suggest sleep is necessary to survive. Rats normally live up to three years, but when scientists deprived them of all sleep they died after three weeks.

Lack of sleep can make people drive as badly as those who are drunk. Caffeine cannot overcome the effects of sleep deprivation.

Sleep gives neurons - which make up our nervous system - a chance to shut down and repair themselves. It also lets the brain exercise neuron connections that otherwise might deteriorate from lack of activity.

Beauty sleep is real. During sleep, the body's cells show increased production and reduced breakdown of proteins - these repair damage from stress and ultraviolet rays.

The parts of the brain that control emotions, social interaction and decision-making are rested during sleep. Research into the nerve signals also shows that in deep sleep we store memories while dreaming.