To examine the sleep habits of 3-year-old children, we questioned guardians during a routine health examination for 3-year-old children at a public health center. According to the 1105 questionnaires analyzed, the proportion of children who fell asleep at 10 p.m. or later was 49.6%. The nocturnal sleep onset time was significantly correlated with the wake-up time in the morning and was significantly negatively correlated with the nocturnal sleep duration. The average daily total sleep duration (nocturnal sleep duration + nap duration) of regular nap-takers showed a significant negative correlation with the nocturnal sleep onset time. The average values for height, weight, and body mass index (BMI) were not correlated with the nocturnal sleep onset time. Children who went to sleep later got less sleep than those who went to sleep earlier. Because sleep debt has a harmful impact on older children and adults, late sleep onset may have adverse health consequences in young children.

No abstract

Background-Children rarely complain of symptoms associated with sleep disordered breathing (SDB). Paradoxical inward rib cage movement (PIRCM) during sleep might prove useful for detecting SDB. Aims-(1) To determine the correlation between the degree of PIRCM and other measures of disordered breathing during sleep. PIRCM occurs physiologically throughout rapid eye movement sleep in neonates, while no PIRCM has been reported during sleep in adolescents. (2) To determine the chronological changes in the degree of PIRCM. Methods-PIRCM was quantified by means of the laboured breathing index (LBI). LBI was determined by respiratory inductive plethysmography; PIRCM accompanies a high LBI. Sleep recordings obtained for 101 subjects for various reasons (aged from 3.5 months to 19 years) were analysed. Results-In 22 records, the minimum SaO 2 value was 90% or more and no obstructive apnoea of more than 10 seconds was observed. In these 22 records, LBI during rapid eye movement sleep decreased significantly with age, reaching the mature low level at 3.3 years of age. In the other 79 records, LBI correlated well with measures of obstructed breathing during sleep. Conclusions-By paying more attention to PIRCM, more obstructed breathing during sleep might be found among children aged 3 years or more.

Gross body movements (GM) during sleep, classified into four GM types by the involved parts of body, were evaluated using two‐dimensional video analysis in five normal children aged 4–12 years. The rate of occurrence of all GM types showed apparent sleep stage dependency. Among four GM types, GM‐1 (GM with axial rotation) was the most frequent. Averaged duration of GM‐1 was the longest. A total of 77.2% of GM‐1 started with the contraction of chin muscle and 35% of total sleep changes (tSC) were related to GM. A total of 5.6% of tSC following GM shifted to the deeper stage. Further evaluation is necessary in order to understand the physiological mechanism of GM.