New study shows why you should get the kids to bed on time

Going to bed at the same time every night could give your child's brain a boost, a recent study found.

Researchers at University College London found that when 3-year-olds have a regular bedtime they perform better on cognitive tests administered at age 7 than children whose bedtimes weren't consistent. The findings represent a new twist on an expanding body of research showing that inadequate sleep in children and adolescents hurts academic performance and overall health.

The latest study considered other factors that can influence bedtime and cognitive development, such as kids skipping breakfast or having a television in their bedroom. After accounting for these, the study found that going to bed very early or very late didn't affect cognitive performance, so long as the bedtime was consistent.

"The surprising thing was the later bedtimes weren't significantly affecting children's test scores once we took other factors into account," said Amanda Sacker, director of the International Center for Lifecourse Studies in Society and Health at University College London and a co-author of the study. "I think the message for parents is…maybe a regular bedtime even slightly later is advisable."

The researchers suggested that having inconsistent bedtimes may hurt a child's cognitive development by disrupting circadian rhythms. It also might result in sleep deprivation and therefore affect brain plasticity—changes in the synapses and neural pathways—at critical ages of brain development.

Sleep experts often focus largely on how much sleep children get. While that is important, "we tend to not pay as much attention to this issue of circadian disruption," said Judith Owens, director of sleep medicine at Children's National Medical Center in Washington, D.C., who wasn't involved with the study.

Insufficient sleep and irregular bedtimes may each affect cognitive development through different mechanisms, Dr. Owens said. "The kid who has both [problems] may beat even higher risk for these cognitive impairments," she said.

The study, published online in July in the Journal of Epidemiology & Community Health, examined data on bedtimes and cognitive scores for 11,178 children.

The children were participants in the U.K.'s Millennium Cohort Study, a nationally representative longterm study of infants born between 2000 and 2002.

Mothers were asked about their children's bedtimes at 3, 5 and 7 years of age. Nearly 20 percent of the 3-year-olds didn't have a regular bedtime. That figure dropped to 9.1 percent at age 5 and 8.2 percent at age 7. Mothers were also asked about socioeconomic and demographic characteristics and family routines.

When the children were 7 years old, they received cognitive assessments in reading, math and spatial abilities. The poorest test scores were recorded by children who went to bed very early or very late, and by those who had inconsistent bedtimes, said Dr. Sacker. But once other factors in the home were taken into account only the inconsistent bedtime was associated with lower scores, she said.

A consistent pattern of sleep behavior mattered. "Those who had irregular bedtimes at all three ages had significantly poorer scores than those who had regular bedtimes," Dr. Sacker said. This was especially true for girls who didn't establish consistent bedtimes between 3 and 7 years old.