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Four-year-olds with shorter than average sleep times have increased rates of "externalizing" behaviour problems, reports a study in the July Journal of Developmental & Behavioral Pediatrics, the official journal of the Society for Developmental and Behavioral Pediatrics. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.
"Preschool children with shorter nighttime sleep duration had higher odds of parent-reported over activity, anger, aggression, impulsivity, tantrums, and annoying behaviours," according to the new research by Dr Rebecca J. Scharf of University of Virginia, Charlottesville, and colleagues. They recommend that parents and health care providers discuss steps to improve sleep habits for preschool-age children with behaviour problems.
Externalising behaviour problems
The researchers analyzed parent responses from a nationally representative study of approximately 9 000 children, followed from birth through kindergarten age. When the children were four years old, nighttime sleep duration was estimated by asking the parents what time their child typically went to bed and woke on weekdays.
On a standard child behaviour questionnaire, parents rated their child on six different "externalising" behaviour problems such as anger and aggression. (Externalising behaviour problems are outward behaviours, distinguished from "internalising" problems such as depression and anxiety.) The relationship between sleep duration and behaviour scores was assessed, with adjustment for other factors that might affect sleep or behaviour.
The average bedtime was 8:39 pm and wake time 7:13 am, giving mean nighttime sleep duration of about 10½ hours. 11% of children were considered to have "short sleep duration" of less than 9¾ hours (calculated as one standard deviation below the average).
On the child behaviour questionnaire, 16% of children had a high score for externalizing behaviour problems. Behaviour problems were more common for boys, children who watched more than two hours of television daily, and those whose mothers reported feeling depressed.
Regular sleep habits
After adjustment for other factors, "Children in the shortest sleep groups have significantly worse behaviour than children with longer sleep duration," Dr Scharf and colleagues write. The effect was greatest for aggressive behaviour problems, which were about 80% more likely for children with nighttime sleep duration of less than 9¾ hours.
Shorter sleep times were also associated with 30- to 46% increases in rates of the other externalizing behaviours studied, including over activity, anger, impulsivity, tantrums, and annoying behaviours. In a linear analysis, as sleep duration increased, troubling behaviours decreased.
Previous studies in smaller groups of children have identified shorter nighttime sleep duration as a risk factor for behaviour problems in preschool children. The average 10½-hour sleep time in this nationally representative sample is less than in studies performed in past decades, and less than currently recommended for four-year-olds.
The new results, along with other recent studies, add to the evidence that preschoolers who sleep less will have more behaviour problems, including disruptive behaviours like aggression and over activity. Although the study can't draw any conclusions about causality, "there is good reason to believe that short nighttime sleep duration leads to externalising behaviours," the researchers write.
Dr Scharf and co-authors recommend that doctors and health care providers ask about bed and wake times when talking to parents about young children with behaviour problems. They add, "Advocating for regular sleep habits, healthy sleep hygiene, and regular bedtime routines may be helpful for young children."
