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.
Within the brain, there are nerve cells that produce neurochemicals called ‘hypocretins’ that regulate wakefulness. The production pattern of hypocretins fluctuates over a 24-hour period. More hypocretins during the day creates a circadian wake drive that is separate from the circadian sleep drive. Wakefulness and sleepiness do not operate like a single electric light bulb dimmer switch that creates more light or more darkness. Rather, there are separate drives for wake and sleep states.
For example, as described by Professor Jamie Zeitzer, many shift workers can readily fall asleep during the day when their shift ends. But they have an inability to sleep for extended periods during the daytime following a night shift (even though they might be exhausted from being awake, even for 24 hours!) because during the day the circadian wake signal messes up their ability to stay asleep. The circadian wake drive is strong in the late evening and helps counter increasing drowsiness at the end of the day, so adults have difficulty napping in the late evening during the ‘forbidden zone’ (Blog Post 94). In adults, the circadian wake drive increases throughout the day and offsets the increasing sleep drive throughout the day so that a single long bout of wakefulness occurs.
Infants and preschool children do not have a single long bout of wakefulness during the day; they nap. What controls infants’ bouts of wakefulness? Do ‘wake windows’ have a biological basis? In this age range, the neurological control over the duration of wakefulness is unknown.
In the sleep literature, the metaphor of a ‘window’ that opens and closes is sometimes used to describe the beginning and ending of these bouts. For example, from the 3rd edition of my book (1987): “During the day, within a one- to two-hour time “window” of wakefulness, your baby will become drowsy and want to go to sleep. I discovered this window during my research on naps.” Some parents misinterpreted this to mean that they should always keep their baby up 1-2 hours after night sleep or after a nap. In subsequent editions, I clarified that this is the maximum time babies can comfortably stay awake. Here are more findings from my research on naps:
| Age (months) | Hours napping (per day) |
| 6 | 1-6 |
| 12 | 1.5-5.5 |
| 18 | 1.5-4 |
| 24 | 1-4 |
Children who take long naps at 6 months tend to maintain long naps until 21-24 months and this is also true for children who take intermediate and short naps (‘Individual stability’ of nap duration). Older children’s nap durations shows no individual stability. Then, children may vary from day-to-day in their total number of hours napping.
| Age (months) | 1 nap/day | 2 naps/day | 3 naps/day |
| 6 | 0 | 84% | 16% |
| 12 | 17% | 81% | 2% |
| 18 | 77% | 23% | 0 |
| 21 | 88% | 12% | 0 |
Young infants might take 2 naps on one day and 3 naps on another day or when older, take 1 nap on one day and 2 naps on another day.
| Age (months) | Number of naps taken (per week) |
| 24 | 7 |
| 36 | 6 |
| 48 | 5 |
| 60 | 4 |
At any age, a child might take many or a few naps per week depending on family circumstances.
So, for all children, there is much variability in the duration of a single nap, the total number of hours napping per day, the number of naps taken per day, and the number of naps taken per week.
My opinion is that paying attention to Drowsy Signs (Blog Posts 9 and 83) that signal the time when soothing to sleep should occur for naps (Blog Posts 53–56, 110, and 118) and bedtime (Blog Posts 123 and 139) is superior to paying attention to a clock and chart describing so-called ‘wake windows’.
Schedules of ‘Wake Windows’ are supposedly designed to help parents determine when to put their child to sleep. However, children who take longer naps can stay awake longer than children who take short naps. The large variability in napping means there is no benefit in watching a schedule of so-called Wake Windows. There is no scientific evidence to support the validity of published ‘wake windows’ schedules. ‘Wake Windows’ are fake.
