Photo courtesy Flickr user National Media Museum under Creative Commons license
Every time you turn around there’s a new report or study about how much sleep adults really need. Not surprisingly, the same is true for children. But what is less known is how sleep affects brain development in very young children. What are the long-term effects of the sleep habits of babies and toddlers? And does it matter when the sleep occurs?
A study released today, conducted by researchers from the University of Montreal and University of Minnesota, found that infants at 12 months and 18 months who get most of their sleep during the night perform better when they reach 18 months and 26 months in “executive functions,” such as their ability to retain information, be flexible in changing environments, and control their attention and impulses. This remained true even after researchers controlled for factors such as parent’s education, income, and the children’s cognitive ability.
The authors reported that this is the first study, known to them, to take a longitudinal look at potential links between early sleep and the development of executive functions, which have been gaining more attention as indicators of children’s likelihood of succeeding in school.
Lead researcher Annie Bernier, professor of psychology at the University of Montreal, and her team recruited 60 families with an infant to participate in the study. The average income among the families was $70,000 (Canadian dollars). The mothers were between the ages of 24 and 45, and 68 percent had a college degree.
According to the report, researchers asked parents to complete three-day sleep journals when their infants were 12 and 18 months. Every half-hour parents were to indicate whether the child was awake or asleep. Additionally, parents were instructed to report any events that could disrupt sleep patterns, such as illness or travel.
Based on the diaries kept by parents, three variables were identified: total hours of sleep, percentage of total sleep occurring between 7 p.m. and 7 a.m. and sleep fragmentation. The number of night awakenings, however, did not appear to have any relation to the infants’ executive functioning.
When the children reached 18 and 26 months of age, researchers gave the toddlers a battery of tests to assess their executive functions and general cognitive ability. One example of the type of test used was Delay of Gratification. For this test, the researcher placed a present under a transparent cup in front of the child. The child was asked to wait until a bell rang to retrieve the present. Researchers repeated the test four times at different intervals: 5, 10, 15 and then 20 seconds. (This test is much like the marshmallow test described in the book Mind in the Making by Ellen Galinsky, who spoke at an Early Education Initiative event in June.)
Based on the journals and the test results, researchers reported several other interesting findings: How long 12-month-old infants slept at night was correlated to their executive functions at 26 months. How long 18-month-old infants slept at night was correlated to their working memory at 18 months and impulse control at 26 months. And in general, children with a higher percentage of sleep during the night were further along in the development of their executive functioning.
“These results raise the possibility that infant sleep impacts developing brain structures in the first two years of life, thereby setting in motion a cascade of neural effects that may carry substantial implications for later executive functioning,” Bernier wrote in the November/December issue of Child Development, which was released today.
From a policy perspective, this research offers insight into the types of resources that perhaps should be included as part of federally funded programs such as home visitation. Home visitation providers could play an important role in educating parents about the importance of sleep and more specifically how it impacts infants’ and toddlers’ skill development in the long run. Additionally, making research like this available to Early Head Start providers and other publicly funded childcare programs would also be important for their communications and engagement activities with parents.