Between-sleep states transitions in premature babies
To assess the manner in which between-sleep state transitions occur in infants, we examined polysomnography (PSG) studies in 25 clinically and neurologically normal, appropriate-for-gestational-age, 30-to-36-week-gestational age (GA) infants. Twenty infants underwent paper PSG and five infants digitised PSG. Sleep states were coded based on concordance of REMs and the electroencephalogram (EEG) pattern. Data were analysed using a multivariate linear model, with the subject factor as a cluster. Duration of active sleep (AS) to quiet sleep (QS) transitions (median 4.8 min) was significantly longer than duration of QS to AS transitions (1.7 min) and was independent from GA and from the recording method (paper vs. digitized PSG). The sequence of modifications in parameters (REM and EEG) was invariable: REM cessation was the first change in AS to QS transitions, and REM appearance was the last change in the QS to AS transitions. Our study demonstrates a stable, well-organized pattern of between-sleep-states transitions in healthy 30-to-36-week GA premature infants. These findings are similar to those described in full-term new-borns and are in agreement with our previous observations of well-defined sleep states at the age investigated here.