Polysomnographic characteristics of healthy elderly subjects with somnambulism-like behaviors.

We compared the sleep characteristics of seven healthy elderly people complaining of nocturnal somnambulism-like behaviors with those of 14 age-matched healthy elderly people who had never shown such behavior. Polysomnographic data revealed the appearance of "Stage 1-REM with tonic electromyographic (EMG) activity" sometimes accompanied by abnormal behavior in the first group, but the sleep architecture and parameters showed no significant difference between the two groups except for higher REM density in the first group. "Stage 1-REM with tonic EMG," observed in the first group was considered equivalent to REM sleep without muscle atonia. It is suggested that both reduced activity of tonic phenomena (muscle atonia) and increased activity of phasic phenomena (higher REM density) of REM sleep are essential for the induction of somnambulism-like behaviors during sleep in healthy elderly subjects.