If you have not already done so, please read Blog Posts 1 through 5 that describe how sleep is important and beneficial. I will post specific information for parents and children based on my book, “Healthy Sleep Habits, Happy Child.” Please do not be put off by my book’s length. This is a reference book. Read only the topic of interest to you.
In older children, the benefit of a nap might be delayed. In a study of children 3–5 years old, emotional memory was enhanced, not immediately after a nap, but following overnight sleep, compared with a no-nap challenge. In other words, there is some interaction between a nap and subsequent night sleep that helps memories to consolidate. This observation highlights the view that, while aspects of sleep may be studied separately, there is interaction among naps, night sleep, bedtimes, night awakenings, time awake after sleep onset, and sleep durations. As a parent, just as we look at the whole child, not merely eye color or smile, we should look at the whole of sleep and not focus on only one part.
A study of children 3–6 years old showed that naps enhance executive function (improving attention in the presence of conflicting information). Furthermore, this benefit was observed in children who habitually always took naps as well as in those who napped inconsistently (less than 90 percent of the time). So even if your child naps infrequently, please try to protect these nap opportunities; there is a real benefit to these naps.
Finally, a separate study of children also 3–6 years old looked at three groups of children based on nap habituality:
Objective measures of sleep showed that on an experimental nap promotion day (children were encouraged to nap between 1:00 and 3:00 P.M. by teachers’ verbal encouragement: “Today is nap day, try to sleep”), total nap sleep time increased for all three groups. Napping did not reduce night sleep. Naturally, there are circumstances where real-life events interfere with your child getting a good nap, and if these events are infrequent, I wouldn’t worry about it. However, a general rule of thumb is to encourage and protect naps as long as possible.
As night sleep and day sleep become more organized, researchers studied the impact of the proportion of total sleep that occurs at night instead of simply the duration of sleep (day, night, and total sleep). Parents’ reports at 3 and 8 months and objective sleep measurements at 8 months showed that a later bedtime was associated with shorter night sleep duration (even though the wake-up time was later), and the parents reported longer day sleep durations resulting in a lower proportion of total sleep occurring at night. The parents whose children had later bedtimes also reported at both time points increased difficulties for their infants settling to sleep, increased latency to sleep (time required to actually fall asleep after being put down), and more time awake during the night. Surprisingly, these parents also reported at both 3 and 8 months an increase of total (twenty-four-hour) sleep duration, but the proportion of total sleep occurring at night was lower.
Another study found that infants at 1 year of age who had a greater proportion of total sleep occurring at night scored higher, at age 4 years, on tests of executive function, reflecting higher abstract reasoning skills, concept formation, and problem-solving skills. This suggests that when a too-late bedtime causes a shorter duration of night sleep, babies may have poor-quality sleep—even those babies who have longer naps, and thus a normal or even a longer twenty-four-hour sleep duration. The two variables, the time of sleep onset (bedtime) and the proportion of total sleep occurring at night, seem to be associated with each other and/or they might be individually important, or one variable might only be a marker for the other. Either way, early bedtimes matter.
Finally, one study of children age 3–6 years with temperamental negative affect (a tendency to react to stressors with high levels of negative emotionality characterized by high discomfort, fear, anger/frustration, aggression, sadness, and low soothability) and late bedtimes were more likely to exhibit externalizing (attention problems or aggression) and internalizing (anxiety or depression) behaviors. The authors stressed that the relations between temperament and behaviors “were not moderated by sleep duration.” Instead, the late bedtime “confers risk for maladaptive outcomes [because it alters] the proportion of time spent in distinct sleep stages [Emphasis added].”
Supporting the idea that late bedtimes alone, and not short sleep durations, might be harmful is a study among 15-year-olds with late bedtimes during the school year. Worse educational outcomes and emotional distress were observed six to eight years later, but short sleep durations were not associated with changes in academic or emotional functioning.
(To be continued.)