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 Children and teens followed until age 20 - when bone mass is peaking
- had lower bone mass at that age the more hours they had spent
watching TV in childhood, researchers reported online July 4th in
the Journal of Bone and Mineral Research.
“What we need to make clear is that it’s not necessarily the act of
watching TV that is driving the link between TV and health outcomes,
but the act of sitting for long periods,” said Natalie Pearson of
the School of Sport, Exercise and Health Sciences at Loughborough
University in the U.K., who was not part of the new study.
“The first set of data collected on TV viewing in the current study
was collected 15 years ago,” and since then more and more young
people have started watching TV on demand, using iPads, smart phones
and apps, she told Reuters Health by email.
For the study, led by Joanne A. McVeigh at Curtin University in
Perth, Australia, the parents of more than 1,000 Australian kids
reported how much TV each child watched per week at ages 5, 8, 10,
14, 17 and 20 years - though at older ages the kids started to
self-report their own TV watching habits.
Researchers sorted the kids into three groups based on their TV
watching patterns over time: about 20 percent watched less than 14
hours of TV per week as children and teens and were considered
consistent low-level watchers, more than 40 percent watched 14 or
more hours per week as children and teens and were consistent
high-level watchers, and 35 percent increased from low to high
levels of TV watching per week over the years.
At age 20 the participants had X-ray scans to assess bone mineral
content.
The researchers accounted for height, body mass, physical activity,
calcium intake, vitamin D levels, alcohol, and smoking at age 20,
and still found that kids who were consistently high-level TV
watchers at younger ages had lower bone mineral content than others
as adults.
Immobilization for prolonged period of time is detrimental to bone
health, said Dr. Sebastien Chastin of Glasgow Caledonian University
in the U.K., who was not part of the new study.
“Sitting watching television does two things, it takes away from
being active, therefore we do not get the benefit of physical
activity and second it immobilizes us for prolonged period of time
which we know from bed rest studies triggers physiological response
that change the balance in our body chemistry that keeps our bone
strong,” Chastin told Reuters Health by email.
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“Several studies have shown over the years that there is a
relationship between the time we spend sitting and bone health,” he
added.
"Poor bone health ultimately can lead to osteoporosis (brittle bone
disease) which affects over 200 million women worldwide," he said.
“You can imagine that a fall on a brittle hip is more likely to
result in fracture.”
Our bodies reach peak bone density around age 22, after which time
bone density decreases over time, though we can slow the decrease by
maintaining an active and healthy lifestyle, Chastin said.
“Impact sports (not contact) are the most beneficial for bone
health,” he said, citing parkour or “free running” in particular for
muscle strength, balance and coordination.
“It is often very difficult to make parents and doctors aware of the
very long term health implications of sitting (at a screen or other
sitting occasions such as school time, work time, travel etc.) for
long periods, as in today’s society we are very interested in the
immediate responses to our actions and not what will happen 20 years
down the line,” Pearson said.
There are practical ways to break up periods of seated screen time,
like getting up during ads or while working on a computer getting up
to answer the phone instead of emailing a colleague or friend, she
said.
SOURCE: http://bit.ly/29uRk1N
J Bone Miner Res 2016.
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reserved.] Copyright 2016 Reuters. All rights reserved. This material may not be published,
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