Too much sitting in childhood is driving osteoporosis, study says
It's time we stopped thinking of osteoporosis as a problem of ageing – the journey towards the snapped wrists and fractured hips we associate with old ladyhood can start in childhood, according to new research.
The Australian study, which tracked the physical activity levels of a group of 10 to 13-year-old children over 10 years, has found that those who spent the most time sitting had 9 per cent lower bone strength in the lower leg.
"In this study we've looked at what happens to bone strength over a long period and this shows the impact that physical inactivity has over time. Although there's a big focus on the risk of overweight and obesity when children are sedentary, there's now growing evidence that it's also having an effect on bone size and strength," says Dr Rachel Duckham, a research fellow at Deakin University's Institute for Physical Activity and Nutrition.
"Inactivity in childhood can also set the pattern for the rest of a child's life – if you're physically inactive at the age of three, then you're likely to be inactive at six and throughout your lifetime."
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When women arrive at menopause – the time when bones can lose density thanks to lower levels of oestrogen – they're blitzed with advice on maintaining bone strength with exercise, calcium-rich food and vitamin D. But it's a message that needs to be louder in childhood and adolescence, the years when we build most of our bone, she adds.
"The more bone we lay down in childhood and adolescence, the stronger our bones will be later in life," explains Duckham whose earlier research at the University of Saskatchewan in Canada found that the most physically active kids become the adults with the strongest bones – regardless of how physically active they are as adults.
"If we want to tackle osteoporosis we need to start in childhood – that's where the disease has its origins," she says.
"We need to encourage children to take part in sports like gymnastics, soccer, and basketball for instance, or activities like jumping, hopping and skipping. These involve dynamic high-impact loading and multi-directional movements which stimulate bone and help it to grow.
"Compared to boys, girls tend to do sports that put less load on the bone. Netball and gymnastics are good but not all girls do them," she says. "Exercises like walking, cycling and swimming are great for cardiovascular fitness – but they don't load the bone."
But if physically inactive kids have lower bone strength because of their lifestyle can more exercise strengthen their bones?
Yes – if you can get them doing at least 30 minutes of moderate to high-impact bone loading activity three times each week, such as running, jumping and skipping or sports such as basketball, volleyball or soccer, says Duckham.
"You could also consider getting kids to do short bouts of high-impact loading such as hopping or jumping 50 to 100 times a day. But I think parents also need to be more aware of the kind of activities that build bone – there is an emphasis on cardiovascular fitness and getting children moving which is great, but just walking isn't going to help build strong bones for life. "
So far, research into children's bone development has been with children with no known health problems but some have conditions that influence how well their bones develop – including children with autism spectrum disorder (ASD).
Children with ASD may shy away from group activities such as sports and gravitate to more sedentary things like watching TV or other screens – and because they're often picky eaters, may not get the nutrients needed for good bone development, explains Duckham.
- Sydney Morning Herald