According to Reuters, 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 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 said.
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
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