Exposure of Higher Screen Time Adversely Linked with Bone Mineral Density in Adolescents

A study on Norwegian students revealed that boys and girls exposed to higher 'screen time' suffer from lower bone mineral density.

Researchers at Arctic University of Norway, Tromso found that teens who were exposed to computer and TV screens for a considerable amount of time risked lower bone mineral density (BMD).  Right from birth, the skeleton grows continually until the end of the teenage years and it reaches peak growth in early adulthood.  This entire process is greatly influenced by nutritional factors and physical activity.

In order to prove the hypothesis that greater screen viewing during the weekend is linked with lower BMD, the researchers worked on the data of 463 girls and 484 boys of ages 15-18 in Tromso region, Norway. These students were a part of the Fit Future Study 2010-2011. This study assessed over 90 percent of all the first year high school students in the region.

Using dual-energy X-ray absorptiometry (DXA) the researchers measured BMD at hip, femoral neck and total body.  With the help of self administered questionnaires and interviews the researchers collected lifestyle variables, this included questions on time spent in front of television or computers daily and the leisure time spent in physical activities. Using the data the researchers analyzed the link between screen time and BMD in a multiple regression model that included certain adjustments for age, sexual maturation, BMI, leisure time physical activity, smoking, alcohol, cod liver oil and consumption of carbonated drinks.

As expected the researchers found that boys were exposed to higher screen time compared to girls. And this high screen time had an adverse effect on the person's BMD. In boys, high screen time was linked to higher BMI. Girls who spent 4-6 hours in front of the computer had higher BMD compared to the counterparts who spent less than 1.5 hours a day.

"Bone mineral density is a strong predictor of future fracture risk. Our findings for girls are intriguing and definitely merit further exploration in other studies and population groups. The findings for boys on the other hand clearly show that sedentary lifestyle during adolescence can impact on BMD and thus compromise the acquisition of peak bone mass. This can have a negative impact in terms of osteoporosis and fracture risk later in life," said lead author of the study, Dr. Anne Winther, Arctic University.

Statistics according to the International Osteoporosis Foundation claim that 1 in 5 men above 5o will suffer a fracture due to osterporosis.