'Striking' rise in computer time seen among teens

NEW YORK (Reuters Health) - The number of hours adolescents spend in front of a computer climbed sharply from 1999 to 2004, a new study shows.

The average high school boy spent 15.2 hours a week using a computer in 2004, up from 10.4 hours weekly in 1999, while computer use among teen girls climbed from 8.8 to 11.1 hours a week, Dr. Melissa C. Nelson of the University of Minnesota in Minneapolis and colleagues found.

Nelson and her team also found that time spent by adolescent girls in modest to vigorous physical activity dropped steadily as they got older, although boys' activity levels remained fairly constant.

While there is a popular perception that people are becoming increasingly sedentary, the researchers note, there is little hard data to back this up. To better understand how adolescents' activity levels change as they grow up -- as well as to determine if the average teen's habits are changing over time -- they looked at data from a five-year study involving 2,516 young people.

The study included a younger group, averaging 12.8 years of age, and an older group averaging 15.8 years; the allowed "for the observation of longitudinal changes from early to mid adolescence and mid to late adolescence."

Girls in both groups spent less time in moderate to vigorous physical activity as they got older, the researchers found. The younger set of girls were active for 5.9 hours a week, but their activity dropped to 4.9 hours weekly when they reached high school age. Among the older group of girls, average time spent being moderately to vigorously physically active fell from 5.1 hours to 3.5 hours a week. Among boys, however, time spent being active only fell among the older teens, from 6.5 to 5.1 hours per week.

Computer activity showed the sharpest increase among boys; from 11.4 hours to 15.2 hours weekly for the younger teens, and from 10.4 to 14.2 hours a week among the older boys. For girls, the only increase in computer use was seen among the older group, from 8.8 to 12.5 hours a week.

"Although technologic advances long have been credited for declines in occupation-related physical activity, these are among the first data-driven findings to suggest that such changes have an important impact on leisure time activity, particularly among youth," the researchers write.

They conclude: "Developing effective health promotion strategies that address a wide array of changing behavioral patterns will be important in promoting long-term health and active lifestyles among adolescents and young adults."

SOURCE: Pediatrics, December 2006.