Sleep states development in the first year of life assessed through 24-h recordings.

Sleep measures have been evaluated in 13 normal infants aged between 2 weeks and 11 months 3 weeks, with 24 h polygraphic records. Values over the whole 24 h period show that quiet sleep (QS) increases with age while paradoxical sleep (PS) and ambiguous sleep (AmbS) decrease; however, when the 24 h period is split into two periods (day-time, night-time) it can be seen that QS increases only during the night-time while PS and AmbS decrease only during the day-time. The QS in older subjects becomes mainly located at the beginning of the night-time period, when particularly long phases take place. The distribution during the night-time of PS (in terms of the amount and of the mean duration of the phases) does not change with age.