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It seems like such a small thing, but according to research out of the United Kingdom, the time you put your child to bed every night makes a big impact on their development.
Professor Yvonne Kelly, Child of our Time Editor and Professor of Lifecourse Epidemiology at the University College London, and her colleagues have conducted studies1 on the impact of consistent bedtimes, consistent mealtimes and limited screen time for young children.
“We have a body of robust evidence that shows very clearly that regular bedtimes really matter when it comes to a child’s health and development over that important first decade of their life,” she says.
Professor Kelly and her colleagues have surveyed almost 20,000 children who are part of the UK Millennium Cohort Study which is following young people born across England, Scotland, Wales and Northern Ireland born in 2000-2001.
While the Australian Sleep Health Foundation says three to five year old children should get 10 to 13 hours of sleep with a minimum of eight and a maximum of 14, Professor Kelly and her colleagues have found that it isn’t necessarily the amount of sleep children get, but rather the regularity in the time they are put to bed.
“We found that it’s not just the number of hours a child sleeps that matters, but also having consistent or regular bedtimes.”
Professor Kelly explains why it’s all about the bedtime.
“The key to understanding all this is circadian rhythms.
“If I travel from London to New York, when I get there, I’m likely to be slightly ragged because jet lag is not only going to harm my cognitive abilities, but also my appetite and emotions.
“That’s for me, an adult.
“If I bring one of my children with me and I want them to do well at a maths test having just jumped across time zones, they will struggle even more than I will.
“The body is an instrument, and a child’s is especially prone to getting out of tune.
“The same thing happens when children go to bed at 8pm one night, 10pm the next and 7pm another — we sometimes call this a ‘social jet lag effect.’
“Without ever getting on a plane, a child’s bodily systems get shuffled through time zones and their circadian rhythms and hormonal systems take a hit as a result.”
The body is an instrument, and a child’s is especially prone to getting out of tune. The same thing happens when children go to bed at 8pm one night, 10pm the next and 7pm another — we sometimes call this a ‘social jet lag effect.’
Dr Sally Staton is a NHMRC Research Fellow and Life Course Centre Research Fellow at the Institute for Social Science Research, The University of Queensland.
She agrees that regularity of sleep patterns is important and has conducted sleep studies in early childhood focusing on the impact of naptimes at childcare and parent work patterns on children’s sleep habits.
“In the context of childcare and home patterns we see evidence of ‘social jet lag’ in which young children’s sleep patterns can be disrupted by as much as four hours across a regular week.”
The impact on intellect
In a 2013 study, Professor Kelly and her colleagues uncovered the relationship between regular and irregular bedtimes on a child’s intellectual development.
“The results were striking,” she says.
“Children with irregular bedtimes had lower scores on maths, reading and spatial awareness tests.
“Interestingly, the time that children went to bed had little or no effect on their basic number skills, and ability to work with shapes.
“But having no set bedtime often led to lower scores, with effects particularly pronounced at age three and the greatest dip in test results seen in girls who had no set bedtime throughout their early life.”
The impact on behaviour
In a follow up study, Professor Kelly and her colleagues found the regularity in a bedtime also impacts how a child manages their emotions and how they behave.
“At age 7, according to parents and teachers, children in the Millennium Cohort Study who had irregular bedtimes were considerably more likely to have behaviour problems than their peers who had a regular bedtime.
“In addition, the longer a child had been able to go to bed at different times each night, the worse his or her behaviour problems were.
“In other words, the problems accumulated through childhood.”
The good news is that the negative effects on a child’s behaviour can be reversed.
“Children who changed from not having to having regular bedtimes showed improvements in their behaviour,” says Professor Kelly.
The impact on obesity
In a 2017 study, Professor Kelly and her colleagues found that with all of the routines they studied, an inconsistent bedtime was most strongly associated with the risk of obesity.
“Children with irregular bedtimes were more likely to be overweight and have lower self-esteem and satisfaction with their bodies,” she says.
“This supports other recent findings which showed that young children who skipped breakfast and went to bed at irregular times were more likely to be obese at age 11.
“Even children who ‘usually’ had a regular bedtime were 20 per cent more likely to be obese than those who ‘always’ went to bed at around the same time.”
A 2018 Australian study adds to the UK findings noting the importance of sleep duration using data from the Effective Early Educational Experiences for children (E4Kids) study.
“The researchers examined a range of sleep parameters and identified short sleep duration as associated with increased Body Mass Index, with effects most prominent for boys,” says Dr Staton.
What impacts a child’s sleep?
Quality early learning centres understand children of the same age can have different sleep rest and relaxation needs which educators and supervisors must consider under the National Quality Framework.
“Our studies now range to a sample in excess of 3,000 children,” Dr Staton says.
“Regularity of sleep is affected by parent work patterns and childcare attendance as children often are required to lie down when at childcare, nap more on childcare days and this affects night bedtime sleep.
“Irregularity relates to days in childcare and days out of childcare.”
Dr Staton emphasises that while a regular bedtime and the number of hours a child sleeps is important in learning, emotional regulation and physical well-being, we need to remember that family lives are often complex.
“While regularity of sleep is clearly important it may well be overly simplistic to suggest that an intervention to compel regularity will be easy to implement or effective in all cases given the complexity of family life, childcare sleep practices and the other factors such as a neurobiological disorder in some children.
“Our team at the Institute for Social Science Research at The University of Queensland along with colleagues at the University of Melbourne are working to understand the impact of social and environmental factors on children’s sleep patterns and child outcomes.”
1 Time for bed: associations with cognitive performance in 7-year-old children: a longitudinal population-based study (2013) & Self-regulation and household routines at age three and obesity at age eleven: longitudinal analysis of the UK Millennium Cohort Study (2017) & Changes in Bedtime Schedules and Behavioral Difficulties in 7 Year Old Children (2013)