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.
As a child grows in length, the bones get longer in either a fairly gradual or continuous fashion or instead, there are periods of no growth alternating with periods of rapid growth, or growth spurts. Different researchers have published papers supporting both points of view. One researcher, promoting growth spurts, claims on her website (Growing Up Human): “How can parents know when their child is experiencing a “growth spurt”? Babies share their discomfort loudly, and need emotional support, comforting and temporary increased food intake. [The growth spurt] can turn even a calm and good-humored child into a whiney, hungry and irritable person with sleep perturbations [emphasis added].” Nowhere in her research (nor any other’s research) is data presented documenting sleep disturbances associated with growth. After multiple email exchanges, the author reneged on her promise to me to share data to support her claim that growth spurts disrupt sleep.
This myth results from the promotion of a book and an app.
An older version of this myth is that when a child was mastering a new motor skill, such as standing without support or walking freely, sleep became disrupted. I routinely asked mothers in my practice who were pediatric physical therapists or pediatric psychologists if they were aware of this notion. They all agreed that they knew about it from their training. When I asked at the age-appropriate visit whether their own child had shown this behavior, they all agreed on the answer: No. The modern version of this myth is called ‘sleep regressions’:
The Wonder Weeks is the English translation of the Dutch book Oei, ik groei! (literal translation: Ai, I’m growing!) by former professor Frans Plooij, originally published in 1992. It has been republished several times, with an updated version published in 2017. It describes the theory that the cognitive development of babies occurs in predictable jumps. However, a follow-up study by Plooij’s PhD student, Carolina de Weerth, failed to find any evidence of predictable leaps. A New York times article concludes: “experts (and parents) agree that sleep patterns can vary wildly throughout a baby’s first two years, no rigorous data support the notion that nap and nighttime changes happen at predetermined times or are linked to specific developmental milestones.” Despite this, the book continues to be popular, and the publisher has produced a mobile app based on the book.
According to the book, a baby should go through 10 predictable jumps or “leaps” in its cognitive development during the first two years, with 8 in just the first year, counted from the due date if the child was premature. These jumps consist of two phases; A phase where the baby is generally unhappy, followed by a period where the baby is generally happy, due to discovering new things with the newly gained cognitive skills. The “leaps” are predicted to occur at 5, 8, 12, 19, 26, 37, 46, 55, 64 and 75 weeks old.
A follow-up study by Plooij’s PhD student, Carolina de Weerth, examined the claims of the book. She tested both behaviour and cortisol levels and failed to find any evidence of greater fussiness or higher cortisol levels corresponding to the leaps. Frans X Plooij tried to prevent the British Journal of Developmental Psychology from publishing her study. Van Geert, a coworker, described his behaviour as “very indecent.” He also described the claims made by the book as contradicting the greater body of research on child development. The controversy over these results that ensued led to Plooij’s firing and departure from academia. [emphasis added]
Some adults have an eveningness preference (owls) while others have a morningness preference (larks). But research in children shows that between birth and 8 years of age, evening types (owls) occurred in less than 2 percent of children at every age. In fact, using objective measures of sleep and salivary melatonin, in the age range of 30-36 months, the number of definite evening types was zero. A parent-response survey, in the same age range, found evening types to be 0.9 percent of children. So the vast majority of babies and young children are larks and benefit from early bedtimes (Blog Post 7) although this statement might not apply to all populations (Blog Post 14). Additionally, among mothers, but not fathers, who are owls, it is more likely that their children will have late bedtimes, require more time to fall asleep after being put down, and have more sleep difficulties. Please respect your child’s natural sleep rhythms (Blog Post 8) and watch for drowsy signs (Blog Post 9), even if you are an ‘owl’.