Before the age of seven, a girl’s cognitive development is greatly affected by a regular bedtime.
Out of the 11,000 children participants in a long-term study, seven-year-old girls who didn’t have regular sleep schedules had IQ scores approximately nine points lower than their peers, based on cognitive tests in reading, maths, and spatial awareness.
Boys without regular sleep schedules seem to only be temporarily affected. The group of researchers at the University College, London found that boys with irregular bedtimes were recorded as having an IQ approximately six points lower than their peers at age three, but this gap diminished by age seven. The researchers have no explanation as to why sleep affects boys and girls differently.
In the past, sleep experts have argued that an earlier bedtime is beneficial for children.
However, the study — published in the Journal of Epidemiology and Community Health‘s July issue — says that it doesn’t matter what time kids go to bed as long as they consistently go to bed at the same time every night.
“I think the message for parents is … maybe a regular bedtime even slightly later is advisable,” Amanda Sacker, director of the International centre for Lifecourse Studies in Society and Health at University College London and a co-author of the study, told Sumathi Reddy in The Wall Street Journal.
The researchers found that brain power is heavily affected by disruptions in the circadian rhythm during childhood years. This means that irregular bedtimes can disrupt a body’s natural development and growth, which then affects the brain’s ability to understand and retain information.
The authors wanted to see whether bedtimes in early childhood were related to cognitive development. All of the participants were born between Sept. 2000 and January 2002, and were visited by researchers at ages nine months and three, five, and seven years.
More than half of the children in the study went to bed between 7:30 and 8:30 p.m. and the researchers also accounted for factors such as skipping breakfast or watching too much television.
Business Insider Emails & Alerts
Site highlights each day to your inbox.