Sleep patterns in mental retardation: Down's syndrome.

EEG and eye movements during two consecutive nights were recorded in 21 "normal" and 21 Down's subjects of both sexes in the 14-24-year age range. Records of most Down's subjects were characterized by longer total sleep time, lack of waking alpha, frequent awakening and movement epochs and fewer spindle bursts. Significantly longer "awake" and stage 4 percentages, but less stage 2, were found in the Down's group. They also had longer REM latency, and lower eye movement density based on number of eye movements. Density based on integrated eye activity correlated positively with IQ in the Down's subjects. Spectrum analysis for EEG frequencies from 1 to 20 c/sec showed significantly greater power in the Down's group below 9 and above 12 c/sec, but no difference in the alpha range. The greater power at low frequencies was more pronounced in "awake", stage 1 and REM.