Sleep - Healthy, natural, regular

Surprisingly little is known about sleep, how to deal with specific issues, and how much is really needed. However, to give the reader some idea of how sleep should be, a healthy sleeper should adjust to a new sleep routine within a few days and be able to then keep to that routine daily, waking up with ease when they need to.

Circadian rhythm

The circadian rhythm is the daily cycle present in living things, from human, to animals and even plants. This rhythm controls the need to sleep and so is a very important aspect of life. The circadian rhythm in humans is approximately 24 hours - this is really seen as being inbuilt and unchangable, but can be influenced by external stimuli, most importantly daylight.

Problems with sleep frequently occur, as the human circadian rhythm is often shown in research to be over 24 hours. This would mean that naturally, a human would get to sleep progressively later each day, eventually completely reversing their sleep/wake cycle. In the modern world, where many people would work increasing long hours indoors, without regular exposure to sunlight to influence their circadian rhythm, a long list of sleep problems exist related specifically to this.

Larks and Owls

Many people would consider themselves either morning or night people - this is scientifically accepted and is very common. Little is known about why, but it is likely caused by

Sleep disorders

Several sleep disorders exist that can cause issues when trying to sleep or trying to stay awake.

• Delayed sleep phase syndrome (DSPS) - causing an offset in the circadian rhythm, causing difficulty getting to sleep, and problems waking up.
• Advanced sleep phase syndrome (ASPS) - the opposite of DSPS, causing difficulty staying awake, and then problems staying asleep in the morning.
• Free-running circadian rhythm sleep disorder - known by several different names, this disorder causes the circadian rhythm to slip everyday, the sufferer steadily sleeping and waking later and later, until their sleep pattern is entirely reversed, and then eventually back to normal for several days.

Light therapy is often used to help deal with these sleep disorders - exposing the sufferer to bright light for a set amount of time can provide an effective treatment. The exact timing of the light exposure is very important, as is the exposure time and the colour and brightness of the light.