Sleep is a complex process. Different parts of the brain control, contribute, and influence sleep at different stages. People normally sleep at night. However, mid-day sleep is also prevalent at some parts of the world.
There are two types of sleep: Non-Rapid Eye Movement Sleep (NREM) or quiet sleep and Rapid Eye Movement Sleep (REM) or active sleep. While sleeping, sleepers usually pass through five stages of sleep.
These stages progress cyclically and are repetitive in nature. Each cycle takes 90-110 minutes to be completed and then begins from the first.
However, sleep cycle does not progress through these stages in sequence. It usually passes through the first four stages disorderly and then enters the last or REM stage after 90 minutes.
After that, a cycle is completed and another sleep cycle begins. Each night, sleepers pass through four or five such cycles. Infants spend almost 50% of their sleeping time in REM sleep while the percentage decreases to 20% in case of adults.
A normal person passes through these sleep stages every night. However, sleeping disorders can disrupt the sleep cycles. Studies have shown that over 40 millions of USA people experience some kinds of sleep disorders but 95 percent of such cases go untreated and undiagnosed simply because of ignorance and indifference.
One of the most common sleep disorders is insomnia. About one-third of the total adult population of the world suffers from some kinds of insomnia. Most of the people suffer from transient or acute insomnia that can be treated easily.
These types of insomnia last for few days to few weeks and go away with the removal of the causes that disturb the sleep cycles. However, chronic insomnia needs medical treatments and therapies to be cured.
Though insomnia is not considered as a fatal problem, it can lead to serious mental and physical troubles. So, proper care and treatment should be applied to insomniac patients.