Sleepwalking is a disorder characterized by walking or other activities a person engaged in while【C1】______ still asleep. It is especially【C2】______ among children. Each night there are several【C3】______ of non-REM and REM sleep. Sleepwalking most often occurs during deep, non-REM sleep early in the night. It can also occur during REM sleep near morning.
The cause of sleepwalking in children is usually unknown【C4】______ may be related to fatigue, 【C5】______ sleep loss, or anxiety. Sleepwalking in adults can be associated with mental disorders, reactions to drugs and alcohol, or disease such as seizures: In the elderly, sleepwalking may be a 【C6】______ of an organic brain syndrome(综合病症) or REM behavior. disorders.
The sleepwalking activity may include simply sitting 【C7】______ and appearing to be awake【C8】______ actually being asleep, getting up and walking around, or【C9】______ activities such as【C10】______ furniture, going to the bathroom, dressing and undressing, and similar activities. Some people even drive a car while actually asleep. The【C11】______ can be very brief or can last for 30 minutes or longer.
One common misconception is that a sleepwalker should not be awaken. It is not dangerous to awaken a sleepwalker,【C12】______ the person may be【C13】______ or disoriented for a short time on awakening. Another misconception is that a person cannot be【C14】______ when sleepwalking. Actually, injuries caused by such things as tripping and loss of balance are common for sleepwalkers. Sleepwalking affects【C15】______ 1% to 17% of children and is more frequently seen in boys. The【C16】______ of sleepwalking decreases with age.
What causes sleepwalking is not known. Sleepwalking【C17】______ no serious health threat to those who experience it, although the risk of injury is a 【C18】______ of concern. Currently, there is nonspecific medical evidence that suggests that there may be psychiatric issues involved in sleepwalking and it is not【C19】______ or treated as a mental illness. Future research may【C20】______ the development of a medical-legal definition of sleepwalking.
【C1】

A. physically
B. unconsciously
C. seemingly
D. mentally