Sleep States in Premature Infants

Abstract

SUMMARY Suggestions that rapid eye movement (REM) sleep is ontogenetically primitive and observations of the behaviour of premature infants led to an attempt to trace the development of sleep in human infants from the premature period to three months after the expected date of delivery. Three sleep states were established, Quiet Sleep, Active Sleep (REM sleep), and Transitional Sleep, for the categorization of each 20 second interval of sleep during lengthy electroence‐phalographic and polygraphic recordings. Criteria regarding observed movements, eye movements, respiratory pattern, heart rate, chin electromyogram, and the EEG were used for a visual analysis of the tracings, with the specification that only four of the six criteria had to be met for classification of a 20 second interval as one sleep state or another. A second analysis, by means of computer sorting, was more rigid in that each 20 second interval had to meet all three criteria regarding observed movement, respiratory pattern, and eye movements. The other criteria were omitted. The second stricter analysis yielded a greater percentage of intervals that could not be called Active or Quiet Sleep and were, therefore, classified as Transitional Sleep, especially below 35 weeks gestational age. This finding/supports the concept that the sleep states of the more premature infants are less well defined and that the simultaneous occurrence of all the necessary criteria, particularly in Active 5jileep, is rarer than at later ages. Both analyses showed that the amount of Quiet Sleep increases as the infant matures, from 10 per cent at 31–32 weeks gestational age to roughly 50 per cent at 3 months past term. Conversely, Active Sleep decreases with maturation, the exact amount depending on the method of categorization. When the records were analysed visually, Active Sleep was found to constitute 68 per cent of the total sleep at 33–34 weeks gestational age and diminished to 36 per cent at 3 months; with computer sorting the comparable figures were 45 per cent and 25 per cent. Nevertheless, the figures for premature infants at term and 3 months were similar to those for full‐term infants at the same ages. The ill‐defined nature of the Active Sleep state in the early gestational ages and its subsequent delineation and diminution in amount amplify previous characterizations of this sleep state as a neurophysiologically primitive state and predecessor of the later stage during which dreaming occurs. RÉSUMÉ EAtats de sommeil chez les prématurés On a suggéré que le sommeil avec mouvements rapides des yeux (REM) est primitif ontogénétiquement; ceci, ajoutéà des observations du comportement des prématurés, nous a amenéà tenter de tracer le développement du sommeil chez les nouveaux‐nés humains depuis la période prématurée jusqu'à trois mois après la date prévue de l'accouchement. Trois états de sommeil ont étéétablis: Sommeil Tranquille, Sommeil Actif (Sommeil REM), et Sommeil Transitoire; pour la caractérisation de chacun d'entre eux on a étudié des intervalles de 20...

Unobtrusive sleep state measurements in preterm infants – A review

“…Subsequently, we will discuss the different measurement methods used to acquire signals connected to sleep states in preterm infants, before discussing some unobtrusive technical means for acquiring these signals. (4,5). More information on the role of each of these sleep states during development is available (6)(7)(8).…”

“…The scoring parameters of both methods can be found in the corresponding publications (16). There are three ways to perform classification using the two methods: the use of PSG methods alone (1,(17)(18)(19)(20), the use of behavioural methods alone (13,14,21,22) and the use of both methods in combination (4,11,16,(23)(24)(25). However, sleep/wake states in EEG or PSG of preterm infants are typically scored manually.…”

The Visual Scoring of Sleep in Infants 0 to 2 Months of Age

“…Earlier infant scoring criteria have tried to reduce the percentages of T sleep scored by permitting scoring if only one, or better yet, two PSG correlates within an epoch are discordant for the sleep state. 24,90 The percentage of sleep time spent in T sleep decreases with increasing infant maturation. Figure 5 shows an example of T sleep.…”

A neurophysiological perspective on sleep and its maturation

“…Although it may appear futile to question to what extent they reflect wakefulness, as this notion cannot be tested in fetal life, some authors have suggested that certain early fetal movements are reminiscent of postnatal movement patterns seen during wakefulness. 18 Clearly rhythmical cycling of motor activity appears between 20 and 28 weeks of gestation 12,19 (Fig. 1).…”

“…In particular, concordance between behavioural and EEG variables is poor. 12 Transition between states occurs discontinuously, relatively frequently over short intervals, and can sometimes be provoked by stimulation at some moments but not at others. This may continue up to the age of 6 months.…”