单项选择题

Sleepwalking is a disorder characterized by walking or other activities a person engaged in while (62) still asleep. It is especially (63) among children. Each night there are several (64) 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 (65) may be related to fatigue, (66) 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 (67) of an organic brain syndrome(综合病症) or REM behavior disorders.
The sleepwalking activity may include simply sitting (68) and appearing to be awake (69) actually being asleep, getting up and walking around, or (70) activities such as (71) furniture, going to the bathroom, dressing and undressing, and similar activities. Some people even drive a car while actually asleep. The (72) 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, (73) the person may be (74) or disoriented for a short time on awakening. Another misconception is that a person cannot be (75) when sleepwalking. Actually, injuries caused by such things as tripping and loss of balance are common for sleepwalkers. Sleepwalking affects (76) 1% to 17% of children and is more frequently seen in boys. The (77) of sleepwalking decreases with age.
What causes sleepwalking is not known. Sleepwalking (78) no serious health threat to those who experience it, although the risk of injury is a (79) of concern. Currently, there is nonspecific medical evidence that suggests that there may be psychiatric issues involved in sleepwalking and it is not (80) or treated as a mental illness. Future research may (81) the development of a medical-legal definition of sleepwalking.