Researchers looked at patterns of screen-time through high school, including total time viewing television, video, computer and the Internet. Then they examined the influence of neighborhood social factors on distinct patterns of screen-time.

"Boys and those whose parents had lower educational attainment were much more likely to be in the 'high-screen time' group," said Tracie A. Barnett, Ph.D., lead author of the study. "Teens with high levels of screen time may be at increased risk of obesity."

They analyzed 1,293 seventh grade students from 10 Montreal high schools. The students in the study had completed in-class questionnaires four times a year for five years, and reported their usual number of hours watching television or videos, and using the computer or surfing the Internet. The researchers defined neighborhoods by census district, looking at average education and income levels within districts.

Barnett and colleagues identified distinct levels of screen-time for each of television/video and computer/Internet use. Overall, their study showed that:

• 52 percent of boys and 26 percent of girls reported average total screen-time levels above 42 hours per week;
• 52 percent of boys and 39 percent of girls reported average levels of TV/video use above 23 hours per week;
• 24 percent of boys and 7 percent of girls reported average levels of computer/Internet use of almost 30 hours per week.

"Most patterns were characterized by sustained levels throughout high school," said Barnett, a researcher at Sainte-Justine Children's Hospital Research Center and assistant professor in the Department of Social and Preventive Medicine at the University of Montreal in Canada.

Approximately 73 percent of girls and 48 percent of boys were in the 'low' total screen-time group, corresponding nevertheless to between 18 and 22 hours of screen-time per week.

However, television still accounts for most of the screen-time, with 85 percent of adolescents reporting less than 10 hours per week of computer/Internet use.

For girls, living in neighborhoods ranked as the lowest third by socio-economic factors increased the likelihood of belonging to the high screen-time group up to five-fold compared to girls in the highest ranked socio-economic neighborhoods.

For boys, living in neighborhoods that had the lowest level of education increased the odds of being in the high screen-time group two- to three-fold, versus their counterparts where education levels were highest.

A more detailed analysis revealed that these associations were more pronounced for television/video watching and weaker for computer/Internet use.

"Researchers need to explore why adolescents' (notably girls') levels of especially television and video screen-time viewing through high school are higher if they live in neighborhoods that are socio-economically disadvantaged," Barnett said. "In the meantime, we should make sure that teens living in these neighborhoods have access to safe and appealing active alternatives to sitting in front of screens."

Co-authors are: Jennifer O'Loughlin, Ph.D.; Marie Lambert, M.D.; Lise Gauvin, Ph.D.; Yan Kestens, Ph.D.; and Mark Daniel, Ph.D.

The National Cancer Institute of Canada funded the study with funds from the Canadian Cancer Society.

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