The term ‘Sleep Consolidation’ is used by sleep researchers in two different ways:
- If a child wakes up during night sleep, the sleep is described as ‘fragmented sleep’ and it is objectively measured by the number of awakenings and the total duration of being awake during the night. The term Wake After Sleep Onset (WASO) is a measurement reflecting fragmented sleep. If a child has very few nighttime awakenings and/or short duration nighttime awakenings, sleep is described as more ‘consolidated’. Children with ‘fragmented night sleep’ have adverse outcomes (Blog Posts 11 and 125).
- However, there are two ways to consider nighttime wakings in children as described by Professor TF Anders:
A. Crying Awakening = “Signaling Awakening”. The child’s cry is a signal to a parent that their baby is awake and needs attention. Some researchers use only these parent reports.
B. Quiet Awakening = “Self-soothing Awakening”. “The child awakens at nighttime and returns to sleep without crying.” Parents are unaware that their baby is awake (Blog Post 145). Some researchers use these objective measures with or without parent reports.
- As infants develop, there is a trend towards less day sleep (fewer and shorter naps). Thus, over time, brain maturation is associated with more of the total 24-hour sleep duration occurring at nighttime. Another way to say this is that the ratio of night sleep duration to total sleep duration ( night sleep duration plus day sleep duration) increases with age. As the percentage of total 24-hour sleep occurring at nighttime increases, sleep is described as more ‘consolidated’. In this sense, more sleep consolidation ( a higher percentage of total sleep occurring at nighttime) is thought to be associated with a more mature brain that has developed more circadian sleep rhythmicity.
Children with immature development of sleep consolidation have adverse outcomes: A 2024 paper showed that those infants, at about 6 months of age, with less sleep consolidation (a lower percentage of total sleep occurring at nighttime) had, at about age 7.5 years of age lower verbal and nonverbal IQ scores. Another way to say this is that infants, about 6 months of age, with longer daytime sleep (naps) durations had lower verbal IQ scores when measured at about age 7.5 years.
