Parents who don't give their toddlers a regular bedtime may have unruly kids down the road.
A study of 10,000 British children has found that those with erratic bedtimes in their preschool years were more likely at age seven to have behavioural difficulties – including hyperactivity, conduct problems and trouble with peers.
The negative effects of irregular bedtimes were cumulative, according to the study published Monday in the journal Pediatrics. Researchers from University College London used data from the U.K. Millennium Cohort Study, which included reports about children's bedtimes and behaviour collected at 3, 5, and 7 years.
As the children without a set bedtime progressed through early childhood, their behavioural scores worsened. However, those who switched to a regular bedtime showed clear improvements in their behaviour, the study found.
"Inconsistent bedtime schedules in the first few years of life might set children onto particular trajectories in relation to their behavioural development," the authors wrote.
The findings are consistent with results from previous research, said Dr. Wendy Hall, a nursing professor at the University of British Columbia.
In a 2007 study of more than 2,000 children in Australia, Hall and colleagues found that sleep problems in a child's third year were a predictor of aggressive behaviour in the child's fourth year of life.
Erratic bedtimes are not necessarily a result of lax parenting, however. Rather, they may be a sign that a child has trouble settling down to sleep – and problems with self-regulation in general, Hall said. "In my view, those difficulties with self-regulatory capacities around sleep also influence a child's self-regulatory capacities in the daytime."
As a sleep expert working with Vancouver families, Hall said, she often sees children whose parents describe them as very alert, socially interactive and difficult to put to bed. "Those children rely heavily on parents to set limits and boundaries for them around bedtime, and around sleep, so that they learn how to self-regulate around sleep," she said.
Skills learned at bedtime may help children self-regulate in other ways, she added.
The authors of the British study suggested that inconsistent bedtimes may affect behaviour by disrupting a child's circadian rhythms, while sleep deprivation resulting from late or random bedtimes may interfere with brain development in regions involved in behaviour regulation. Both are reasonable theories, Hall said, but she noted that bedtimes would have to vary by hours, not minutes, to disrupt a child's circadian rhythm enough to affect behaviour.
Fortunately, the effects of inconsistent bedtimes in young children appear to be reversible. The researchers from University College London suggested that nurses and family physicians could make a habit of asking about children's bedtimes during checkups.
Hall agreed: "Sleep is a public-health issue."