Objective: This was a nationwide study of sleep circadian in term infants. The aim was to understand the development characteristics of infants' sleep/wake patterns longitudinally in their own home environments over the first 12 months of life.
Method: Totally 524 healthy term infants from 9 urban districts took part in this project Their sleep/wake patterns over 24 h were recorded using parental sleep diaries, from the 2nd day to 12 months old.
Result: The results showed that infant daytime sleep changed significantly at 0-2, 3-4, 5-6, and 8-9 months after birth, and the change was the fastest in the first month, the mean percentage of daytime sleep decreased from 82.4% at Day 2 to 62.8% at 1 month old. Also, the average number of naps reduced from 3.7 to 2 across the infancy. The ability of continuous sleep throughout the night gradually enhanced from 1 month old, and the nocturnal longest sleep time extended to 6.8 h at 4 months of age as well as the nighttime awakening frequency less than 0.5 over 6 months old. Additionally, the nighttime sleep increased significantly at 4 and 9 months after birth, where the proportion of nighttime sleep increased from 55.8% at Day 2 to 64.3% of 4 months and 71.2% of 9 months respectively. In general, the total sleep time over a 24 h period presented a downward trend as the infant aged.
Conclusion: The periods 0-6 and 8-9 months after birth were the key periods for the development of infant sleep.