Journal scan

Long hours spent watching TV or computer screens affects teenage boys’ bone health

Teenage boys who spend a large amount of their leisure time using computers or watching TV have poorer bone health than peers who limit their screen time, suggests a large study in Norway.

Lower bone mineral density was linked to weekend screen time in teenage boys

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The study involved 961 school pupils aged 15 to 17, who were assessed in 2010/11 and two years later in 2012/13.

Participants were asked how much time they spent on their computers or watching TV at the weekend and outside of school hours during the week. They were also asked about physical activity and other factors that could affect bone health. Bone mineral density was assessed at the hip, top of the thigh bone (femoral neck), and the whole skeleton.

Boys had higher levels of screen time than girls, averaging around five hours a day at the weekend and just under four hours per day during the week; the equivalent figures for girls were four and three hours. However, 20% of the girls and 26% of the boys who reported more than four hours daily screen time during weekends also spent more than four hours a week on sports and hard training.

Lower bone mineral density was linked to weekend screen time, but the association was only significant among boys. Among girls, four to six hours of weekend screen time daily was associated with higher bone mineral density.

The conflicting results may point to the influence of hormones on the relationship between fat and bones, say the researchers.

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