Normal sleep has 2 cycles: NREM (Non Rapid Eye Movement) and REM (Rapid eye movement). In which, the NREM cycle is divided into 4 stages.

Sleep disorders are very common in medicine in general and in psychiatry in particular. Sleep disorders can seriously interfere with normal physical, mental, social activities and have a major impact on emotions.

Sleep disorders are a common symptom in all age groups, occurring more in women than men, especially in the elderly. In our country, the trend of sleep disorders has increased rapidly in the elderly in recent years.

Sleep is a part of everyone's life and sleeping position has an important influence. Some people choose to sleep on their right side, others choose to sleep on their left side, not knowing which side is better.