Nineteen electroencephalographic (EEG) sleep measures describing four
physiologic aspects of sleep behavior (i.e. sleep continuity, EEG spec
tra, body and eye movements, and autonomic measures) were derived from
visual and computer analyses of 71 24-channel, 3-hour EEG sleep recor
dings on 52 healthy preterm neonates from 28-36.5 weeks postconception
al age (PCA). Forty-eight subjects were neurodevelopmentally normal up
to 2 years of age. Four electrographic states that comprise trace dis
continu of the preterm neonate were defined in terms of increasing sec
onds of EEG quiescence per minute, A regression analysis was performed
after transformations of nonlinear data sets representing the 19 EEG
sleep measures, with the four sleep states as outcome variables. Postc
onceptional age was also included in these analyses as the 20th explan
atory variable. Four measures best defined the EEG sleep states, expla
ining 75% of the variance: decreasing rapid eye movements per minute,
decreasing numbers of spontaneous arousals per minute, increasing spec
tral theta energies, and decreasing facial movements per minute. Other
cerebral and noncerebral measures, including total spectral EEG energ
ies. spectral EEG energies in three bandwidths (i.e. delta. alpha, bet
a), cardiac and respiratory measures, and body movements, did not cont
ribute as significantly to the prediction. Inclusion of PCA into the r
egression equation with the four EEG measures, selected by the analysi
s procedure, indicated that its contribution to state prediction was a
lso small. the effect of PCA on state was found to be explained by the
four EEG sleep measures.