There is something to be said for the conventional wisdom of sending children to bed at a regular hour each evening.
New research, from the University College of London and published in the Journal of Epidemiology and Community Health, indicates that youngsters who had regular bedtime or who went to bed later than 9 p.m. had lower scores in reading and math. The impact was measurably higher throughout early childhood in girls.
The researchers, led by Prof. Amanda Sacker from University College of London, said it was possible that inconsistent bedtimes were a reflection of chaotic family settings, rather than disrupted sleep, that appeared to have a greater impact on cognitive performance in children.
"The take-home message is really that routines do seem to be important for children," Sacker told the BBC. "Establishing a good bedtime routine early in childhood is probably best, but it's never too late."
The researchers gathered data on children at the ages of three, five and seven to find out how well they were doing with their learning and whether their cognitive skills were related to sleeping habits. Erratic bedtimes were most common at the age of three, when one in five of the children went to bed at varying times. By the age of seven, more than half of the children had a regular bedtime of between 7:30 p.m. and 8:30 p.m.