Sleeping pattern of kindergartners and nursery school children: function of daytime nap.

With a questionnaire answered by parents this study investigated the sleeping pattern of children attending kindergartens or nursery schools and the function of an afternoon nap. Sleeping pattern was investigated by a questionnaire with 441 young children (229 boys and 212 girls) attending kindergartens or nursery schools at the ages of 3 to 6 years old. Nighttime sleep did not show any significant change, while daytime naps decreased drastically and almost disappeared by the age of 6. Nursery school children went to bed later at night, so nighttime sleep was shorter than that of kindergartners. They also reported having more 'difficulty to fall asleep', more frequent 'staying-up at late night', less 'not getting enough sleep', worse 'mood at rising', and more 'unwillingness to go to their schools'. To investigate whether afternoon naps, which are routine at Japanese nursery schools, can compensate for sleep insufficiency on the previous night and whether they have the effect of delaying the onset of the subsequent nighttime sleep, we compared sleep duration on the previous night and the sleep onset time between the days with and without an afternoon nap. The afternoon nap appeared to cause delayed sleep onset but was not a result of sleep deficiency.