Tuesday August 4, 2009, 9:24 am
American and Spanish researchers examined the association between sedentary behavior and blood pressure in 111 boys and girls, 3 to 8 years old. For seven days, the children wore a special device that recorded their activity levels. In addition, their parents reported how much time the youngsters spent watching TV, playing video games, painting, sitting or doing other low-level activities.

The researchers also measured the children's height, weight, fat mass and blood pressure.

TV time was defined as time spent watching TV, videotapes or DVDs. Screen time was defined as the total amount of time using a TV, video, computer or video game.

The children were sedentary an average of five hours a day and had an average of 1.5 hours of screen time each day. Boys spent more time using computers than girls, but they spent about the same amount of time on other sedentary behaviors.

"Sedentary activity was not significantly related to systolic blood pressure [the top number in a reading] or diastolic [bottom number] blood pressure, after controlling for age, sex, height and percentage of body fat," wrote David Martinez-Gomez, of Iowa State University and the Spanish National Research Council in Madrid, and his colleagues. "However, TV viewing and screen time, but not computer use, were positively associated with both systolic blood pressure and diastolic blood pressure after adjusting for potential confounders."

They noted that children with the lowest amount of TV and screen time had lower levels of systolic and diastolic blood pressure than kids with the highest amounts of TV and screen time.

"The results of this study showed that TV viewing and screen time were associated with elevated blood pressure independent of body composition in children," the researchers wrote.

"Given that total objective sedentary time was not associated with elevated blood pressure, it appears that other factors, which occur during excessive screen time, should also be considered in the context of sedentary behavior and elevated blood pressure development in children," they concluded.

The study appears in the August issue of Archives of Pediatrics & Adolescent Medicine.

The researchers noted that rising rates of childhood obesity are a major public health issue, with obesity's effects on blood pressure an area of particular concern.

"The clustering of cardiovascular disease risk factors in overweight youth suggests that risks may be immediate and not just indicative of potential future problems," they wrote.

More information

The Nemours Foundation has more about overweight and obese children.