Physical health

About 80% of our sleeping is of the SWS variety, identified by slow brain waves, relaxed muscles and deep breathing.

Deep sleep is important for the consolidation of memories. New experiences get moved to long-term storage and less important experiences from the previous day get cleared ou...

A day or two of sleep deprivation can cause healthy people to suffer hallucinations and physical symptoms.

Cognitive abilities are impaired after a poor night's sleep. Concentration and memory are affected, and people are more likely to be impulsive.

We have a gene that releases a protein that builds up in cells overnight and gets broken down in the daytime. The clock gene is active in almost every cell type in the body and under circadian control.

Virtually every activity in our bodies - related to the blood, liver, kidneys and lungs a...

Poor sleeping habits are not a modern problem.

One study found tribes that don't have access to modern electrical devices to be prone to intermittent sleep. The main difference is that they do not have anxiety about their sleep patterns like western countries do.

Our bodies are synchronized with the day-night cycle as our planet rotates. Our circadian rhythms continue even in the absence of any external input. Even plants that are kept in a dark cupboard at a stable temperature open and close their leaves as though they can sense the sun.

Dreaming accounts for 20% of our sleeping time.

The length of dreams can vary from a few seconds to almost an hour. During REM sleep, the brain is highly active. The muscles are paralyzed, and the heart rate increases. Breathing can become erratic.