Exercise, screen time, snacks and sleep: How Australian pre-teens compare

Gwenevere Joyce and her dad Frank.
Gwenevere Joyce and her dad Frank.  Photo: Chris Hopkins

Prepubescent children in Australia are spending about 11 hours sitting each day, almost half of it on screens, and more than a quarter of them are overweight, research has found.

They're also sleeping more than their counterparts across the world, according to a national study.

For the first time in Australia, researchers led by Murdoch Children’s Research Institute tested everything from weight, cholesterol, lung function, hearing, snacking habits and sleep in more than 1800 children aged 11 to 12 across 30 cities and regional areas to measure the health of children on the cusp of adolescence.

Gwenevere Joyce and her dad Frank.
Gwenevere Joyce and her dad Frank.  Photo: Chris Hopkins

A biological parent of each pre-teen also underwent 20 identical tests to determine how much of their child's health was hereditary or influenced by environmental factors.

Australian children were only getting about half the nationally recommended physical activity they need for their growth and development, the Child Health CheckPoint study found.

Boys were far more active, averaging about 40 minutes of physical activity a day, compared to girls who only recorded about 24 minutes – just a third of the national recommended 60 minutes for pre-teen children.

 

But Melbourne grade six pupil, Gwenevere Joyce, 11, is bucking the trend. She spends about four nights a week at a mix of Irish dancing, ballet and swimming classes.

"I also play basketball or soccer sometimes at school and my friends are pretty active because we are running around a lot," she said.

Advertisement

Alarmingly, poorer children are averaging about 60 minutes more screen time a day than those from wealthier families. Screen use comprises about 40 per cent - or five hours - of the 11 hours the average child spends sitting each day. Australian and international guidelines recommend two hours of screen use per day for children.

Children in lower-socio economic families spend more time watching television and playing video games compared to those from affluent families, who spend an extra hour a day on school-related activities like reading or homework.

 

"It's very concerning that it's not equal," paediatrician and researcher Professor Melissa Wake said. "We don't have an equal society when it comes to the choices kids make about how they spend their time and therefore how they lay down the basis for their future health."

Worried about long-term health effects, Gwenevere's dad, Frank, 49, has limited his daughter's screen time during the week and she is encouraged to read each night.

"She doesn't have a phone yet, but we do try to minimise her screen time and on the weekend we'll often plan to do something active like going for a family bike ride," he said.

While most children tested were deemed healthy overall there were wide variations in results for their weight, blood cholesterol, fitness, and kidney and lung function, which posed serious concerns, Professor Wake said.

"What we're already seeing is that children are already starting to line up on separate trajectories that will have quite profound implications for their health and their well-being as adults," she said.

Children who measured poorer health outcomes were at far greater risk of developing diabetes, heart and lung disease, cancer and osteoporosis in adulthood.

"The seeds [for those diseases] are sown in childhood and we're really seeing evidence of this in the unique new data set," Professor Wake said.

Children’s eating habits were also examined, with researchers finding definite parallels between snack consumption. Parents who ate larger snacks were more likely to have children who mirrored those eating habits.

"I am a bit of a sweet tooth," Mr Joyce said. "But we are very conscious about lunch boxes and ensuring our kids have a healthy range food."

About 27 per cent of children were overweight. But their parents fared much worse, with two thirds of adults deemed overweight or obese.

 

It was not always inevitable, however, that children inherit the body shape or weight of their parents. Researchers only identified a moderate link between an 11 to 12-year-old child’s Body Mass Index and that of their parents.

“Our research suggests that far more than family, environment drives the current obesity endemic," Dr Susan Clifford, the study's lead researcher, said. "Parents are, to some extent, nutritional gate-keepers for their children, but children spend a lot of time at school and with friends and in other environments not shared with their parents.”

As part of the national snapshot, more than 1200 children and their parents wore a wrist accelerometer for eight days which measured unbroken stretches of sitting time.

Pre-teens were spending almost half the day sedentary, while their parents weren't far behind, sitting for about nine hours a day.

 

Children were sleeping an average of nine hours and 25 minutes a night, in line with national sleep guidelines. This was about 20 to 60 minutes longer than children in the US and up to two hours longer than pre-teens in Asia.

But it's a phenomenon that's not clearly understood. Researchers pointed to a combination of environmental factors like traffic noise, parenting styles and family routines, and genetic causes such as the rate and timing of melatonin and serotonin release, which regulate sleep cycles.

 

About 80 per cent of bone health is inherited, while researchers observed small to moderate cross-generational similarities between a child and a parent's lung and heart health.

"The thing that most concerns me is the children at the bad end of the spectrum," Professor Wake said.

"Most of those children are asymptomatic now, they're not sick, but we can see they are kids who are at risk of developing so many problems as adults. The big question now is how do we respond to the challenge of trying to change the trajectories of those kids and what are the interventions we can use to bring about change."

But Professor Wake said there remained hope with the research to be used to create new ways to prevent and treat illness.