Sleep is ubiquitous during infancy and important for the well-being of both infant and parent. Therefore, there is large interest to characterize infant sleep with reliable tools, for example by means of combining actigraphy with 24-h-diaries. However, it is critical to select the right variables to characterize sleep. With a principal component analysis, we identified 5 underlying sleep composites from 48 commonly used sleep variables: Sleep Night, Sleep Day, Sleep Activity, Sleep Timing, and Sleep Variability. These composites accurately reflect the known changes of sleep throughout infancy as Sleep Day (representing naps), Sleep Activity (representing sleep efficiency and consolidation), and Sleep Variability (representing day-to-day stability) decrease across infancy, while Sleep Night (representing nighttime sleep) slightly increases and Sleep Timing becomes earlier with increasing age. Additionally, we uncover interesting dynamics between the sleep composites and demonstrate that infant sleep is not only highly variable between infants but also considerably dynamic within infants across time. Interestingly, Sleep Day is associated with behavioral development and therefore a potential marker for maturation. We recommend the use of sleep composites or of those specific single variables, which are solid representatives of the sleep composites for more reliable research.

中文翻译：

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婴儿睡眠的主要方面是什么？婴儿期复合睡眠的动态

婴儿期睡眠无处不在，对婴儿和父母的健康都很重要。因此，人们非常关注使用可靠的工具来表征婴儿的睡眠，例如通过将书法与24小时制结合使用。但是，选择正确的变量来表征睡眠至关重要。通过主成分分析，我们从48个常用睡眠变量中确定了5种基础睡眠复合物：睡眠夜，睡眠日，睡眠活动，睡眠时间和睡眠变异性。这些复合材料准确反映了婴儿期的已知睡眠变化，如整个婴儿期的“睡眠日”（代表小睡），“睡眠活动”（代表睡眠效率和巩固）以及“睡眠变异性”（代表日常稳定性）降低，“睡眠之夜”（代表夜间睡眠）略有增加，并且“睡眠时间”随着年龄的增长而变得更早。此外，我们发现了复合睡眠之间有趣的动态关系，并证明婴儿睡眠不仅在婴儿之间变化很大，而且随着时间的推移在婴儿内部也有很大变化。有趣的是，“睡眠日”与行为发展有关，因此是成熟的潜在标志。我们建议使用睡眠复合物或那些特定的单个变量，它们是睡眠复合物的可靠代表，可以进行更可靠的研究。我们发现了复合睡眠之间有趣的动态关系，并证明婴儿睡眠不仅在婴儿之间变化很大，而且随着时间的推移在婴儿内部也有很大变化。有趣的是，“睡眠日”与行为发展有关，因此是成熟的潜在标志。我们建议使用睡眠复合物或那些特定的单个变量，它们是睡眠复合物的可靠代表，可以进行更可靠的研究。我们发现了复合睡眠之间有趣的动态关系，并证明婴儿睡眠不仅在婴儿之间变化很大，而且随着时间的推移在婴儿内部也有很大变化。有趣的是，“睡眠日”与行为发展有关，因此是成熟的潜在标志。我们建议使用睡眠复合物或那些特定的单个变量，它们是睡眠复合物的可靠代表，可以进行更可靠的研究。