[Longitudinal study on infantile nocturnal sleep-wake pattern developmental trajectory with Actiwatch]

To understand the infantile nocturnal sleep-wake pattern developmental trajectory with Actiwatch, which would benefit the clinical assessment of infantile sleep.

This study was a longitudinal study conducted between 7 Oct, 2009-30 Oct, 2011 in 10 hospitals of 9 cities of China ( Beijing, Xi'an, Qingdao, Wuhan, Changsha, Chongqing, Huzhou, Xiamen and Liuzhou). Actiwatch was used to track the sleep-wake pattern development trajectory of healthy infants in the first year of life in the home setting. Participating infants were followed up at 10th day and 28th day during the first month, and then monthly from the second to the sixth month after birth, and then at ninth and twelve months of age respectively. Meanwhile, infantile sleep was observed continuously for about 60 hours at each visit. According to the characteristics of repeated measurement data of this study, two-level random effect model was adopted to analyze the trend of infantile nocturnal sleep-wake parameters changing with age, and the gender difference.

A total of 473 healthy infants were included in this study, among whom 246 (52.0%) were boys, and 227 (48.0%) were girls; 355 (75.1%) infants completed the whole year follow-up survey. With infants' age increasing, the latency of infants' nighttime sleep onset decreased from 66.8 minutes on 10th day to 15.5-18.7 minutes at 6-12 months of age. The number of night wakes also decreased with age, while uninterrupted sleep periods lengthened with age. On the 10th day, there were 3.0 times of nightwaking on average, and the longest continuous sleeping interval lasted for 227.6 minutes on average. At 12-month of age, infants could sleep continuously for 350.9 minutes at most on average, while the number of nightwaking decreased to 1.6 times per night on average. Generally, nighttime sleep efficiency increased from 66.3% on the 10th day to 86.3% at 12-month of age. The differences of sleep-wake patterns between boys and girls presented as boys' nocturnal longest uninterrupted sleep period was 19 minutes shorter(266.6 vs. 285.6 min), and the average nighttime sleep efficiency was 2.2% lower (74.2% vs. 76.4%) compared with girls respectively. And the differences of sleep efficiency between boys and girls reduced gradually along with the growth.

During the first 6 months after birth, infantile sleep-wake pattern undergo obvious change. The capability of sleep-onset and uninterrupted sleep improved with age, and the sleep efficiency increased.