Kids who watch a lot of television may build less bone during critical years, and be more vulnerable to osteoporosis and bone breaks later in life as a result, a new study suggests.
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 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 UK, 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.
At age 20 the participants had X-ray scans to assess bone mineral content.
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 UK’s Glasgow Caledonian University.
“Several studies have shown over the years that there is a relationship between the time we spend sitting and bone health.”
“Poor bone health ultimately can lead to osteoporosis (brittle bone disease) which affects over 200 million women worldwide,” he said.
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.
Free running in particular is good for muscle strength, balance and coordination. 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 or take short walks.
