IN THAT mythical era when children were seen and not heard, and did as they were told without argument, everyone knew that regular bedtimes were important. “Dream on!” most modern parents might reply.
But research by Yvonne Kelly of University College, London, shows that the ancient wisdom is right—half the time. Daughters, it seems, do benefit from regular bedtimes. Sons do not.
Dr Kelly knew of many studies that had looked at the connection between sleep habits and cognitive ability in adults and adolescents. All showed that inconsistent sleeping schedules went hand in hand with poor academic performance. Surprisingly, however, little such research had been done on children. She and a team of colleagues therefore examined the bedtimes and cognitive abilities of 11,178 children born in Britain between September 2000 and January 2002, who are enrolled in a multidisciplinary research project called the Millennium Cohort Study.

The bedtime information they used was collected during four visits interviewers made to the homes of those participating in the study. These happened when the children were nine months, three years, five years and seven years of age. Besides asking whether the children had set bedtimes on weekdays and if they always, usually, sometimes or never made them, interviewers collected information about family routines, economic circumstances and other matters—including whether children were read to before they went to sleep and whether they had a television in their bedroom. The children in question were also asked, at the ages of three, five and seven, to take standardised reading, mathematical and spatial-awareness tests, from which their IQs could be estimated.
Dr Kelly’s report, just published in the Journal of Epidemiology and Community Health, shows that by the time children had reached the age of seven, not having had a regular bedtime did seem to affect their cognition, even when other pertinent variables such as bedtime reading, bedroom televisions and parents’ socioeconomic status were controlled for. But that was true only if they were female. On the IQ scale, whose mean value is 100 points, girls who had had regular bedtimes scored between eight and nine points more than those who did not.
Boys were not completely unaffected. Irregular bedtimes left their IQs about six points below those of their contemporaries at the age of three. But the distinction vanished by the time they were seven.
This difference between the sexes is baffling. Dr Kelly did not expect it and has no explanation to offer for it. As scientists are wont to say, but this time with good reason, more research is necessary.
Meanwhile, in the going-to-bed wars most households with young children suffer, the sons of the house have acquired extra ammunition. Mind you, those with the nous to read and understand Dr Kelly’s results are probably not suffering from their sleep regimes anyway.

Jesús Romero Trillo