Causal links between disrupted sleep and behavioral problems in nonclinical populations are far from clear. Research questions were as follows: Are bedtime schedules associated with behavioral difficulties? Do effects of bedtime schedules on behavior build up over early childhood? Are changes in bedtime schedules linked to changes in behavior?
Data from 10 230 7-year-olds from the UK Millennium Cohort Study, with bedtime data collected at 3, 5, and 7 years, and behavioral difficulties scores as rated by mothers and teachers were analyzed.
Children with nonregular bedtimes had more behavioral difficulties. There was an incremental worsening in behavioral scores as exposure through early childhood to not having regular bedtimes increased: mother rated (nonregular any 1 age, β = 0.53; nonregular any 2 ages, β = 1.04; nonregular all 3 ages, β = 2.10, P < .001) and teacher rated (β = 0.22, β = 0.73, β = 1.85, P < .001). Difference in differences analysis showed that for children who changed from nonregular to regular bedtimes there were clear nontrivial, statistically significant improvements in behavioral scores: A change between age 3 and 7 corresponded to a difference of β = −0.63, and a change between age 5 and 7 corresponded to a difference of β = −1.02). For children who changed from regular to nonregular bedtimes between ages 5 and 7 there was a statistically significant worsening in scores, β = 0.42.
Having regular bedtimes during early childhood is an important influence on children’s behavior. There are clear opportunities for interventions aimed at supporting family routines that could have important impacts on health throughout life.
Comments
The Complicated Association Between Sleep Problems and Behavior Problems
In "Changes in bedtime schedules and behavioral difficulties in 7- year-old children," Kelly, Kelly, and Sacker report that children who changed from a non-regular to a regular bedtime between ages 5 and 7 experienced a significant decline in behavior problems. They also report that children who changed from a regular bedtime to a non-regular bedtime between 5 and 7 experienced a significant, but smaller, increase in behavior problems. We applaud the authors' test of the reversibility of behavior problems associated with a non-regular bedtime. We have conducted similar tests of the reversibility of aggressive behaviors associated with sleep problems in the US; however, our models also address directionality, whereas Kelly and colleagues modeled only the pathway from sleep to behavior. As Kelly et al. noted, the direction of the causal link between sleep problems and aggression is unclear. While it is plausible that a lack of sleep leads to elevated aggression, it is also plausible that aggressive behavior disturbs sleep. Children who are aggressive may be unusually resistant to bedtime, find it difficult to fall asleep, or be frequently wakened by nightmares.
We analyzed data from the Early Head Start Research and Evaluation Project, a low-income sample of children followed longitudinally (analytic sample n = 1,782). We examined sleep problems (a count of has trouble getting to sleep, talks or cries out in sleep, wakes up often at night) and aggression, both reported by mothers at child ages 3 and 5. Like Kelly and colleagues, we adjusted for parenting behaviors as well as demographic characteristics, and made use of difference-in-difference models to test the robustness of our findings. We found that children who experienced an increase (1 or more standard deviations [SD]) in sleep problems between ages 3 and 5 had a spike in aggression during this period (beta = 0.15, p < .001), while children whose sleep problems declined (1 or more SD) showed a reduction in aggression (beta = -0.19, p < .001).
Not only did changes in sleep problems predict changes in aggression, but the reverse was also true. We found that an increase (1 or more SD) in aggression between ages 3 and 5 predicted an increase in sleep problems (beta = 0.16, p < .001), while a decrease in aggression (1 or more SD) predicted a similarly sized decline in sleep problems (beta = -0.13, p < .001). These results demonstrated that a change in aggression predicted a change in sleep problems, and that a change in sleep problems predicted a change in aggression.
We therefore urge practitioners to consider the bi-directionality, as well as the reversibility, of the association between sleep problems and behavior problems.
Conflict of Interest:
None declared