NEW DATA ON THE ONTOGENY OF THE CHILDS SLEEP WAKE RHYTHM

The present study is part of a broader body of research concerning the ontogeny and regulations of the young child's sleep-wake rhythm. It was carried out with 12 children admitted to a day-care center from 4 or 5 months of age. None of the children showed any anomalies or functional disorders. The method used in this study consisted in organizing a data collection on the alternations of wakefulness and sleep as well as on the children's behavior throughout the 24-h period, both in their family and at the day-care center from 4 to 15 months of age. The main findings are (a) the circadian rhythm of wakefulness and sleep is clearly set up as early as at 4 months of age and consolidates between 6 and 7 months; (b) some ages are characterized by significant changes in the daily distribution and duration of sleep spans: 6 to 7 months; 10 to 12 months; 13 to 15 months; (c) these changes suggest the existence of several ultradian rhythmicities which become successively prevailing from one age to the next throughout child development. The longitudinal study of the young child's sleep-wakefulness rhythm allows better evaluation of the influence of developmental factors in its structuralization and formulation of new hypotheses on its disorders and dysfunction. Individual factors are under study.