Sedentary behaviors such as TV viewing and "screen time" involving computer use, videos and video games appear to be associated with elevated blood pressure in children, independent of body composition, according to a report in the August issue of
The recent trend in obesity is a major public health concern and its effect on blood pressure is of particular concern, according to background information in the article. "The clustering of cardiovascular disease risk factors in overweight youth suggests that risks may be immediate and not just indicative of potential future problems," the authors write. Although elevated blood pressure is associated with genetic factors, healthy physical, dietary and sleep habits seem to be relevant contributors to blood pressure levels in children. However, there have not been any clear links between sedentary behavior and elevated blood pressure in children younger than age 9.
David Martinez-Gomez, B.Sc., of Iowa State University, Ames, and the Spanish National Research Council, Madrid, Spain, and colleagues examined associations between sedentary behavior and elevated blood pressure in 111 young children (57 boys and 54 girls ages 3 to 8). Sedentary behavior was determined by an accelerometer generally worn over the right hip and by parental reports stating the average time the children spent watching TV, playing video games, painting, sitting or taking part in other activities with low levels of physical activity each day for seven days. Time watching TV was defined as time spent watching TV, videotapes or DVDs. Computer use was defined as the time spent using a home computer or video game. Researchers defined screen time as the total amount of time each child spent using a TV, video, computer or video game. The children's height, weight, fat mass and systolic (top number) and diastolic (bottom number) blood pressure were also measured.
The children's average sedentary time and screen time per day were five hours and 1.5 hours, respectively. Boys spent more time using computers than girls, but there were no significant differences in time spent on other sedentary behaviors. "Sedentary activity was not significantly related to systolic blood pressure or diastolic blood pressure after controlling for age, sex, height and percentage of body fat. 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," the authors write. "Participants in the lowest tertile [one-third] of TV and screen time had significantly lower levels of systolic and diastolic blood pressure than participants in the upper tertile."
"In conclusion, 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 authors write. "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."
This work was supported in part by a York University Faculty of Arts Research Grant, American Heart Association Beginning-Grant-in-Aid, a University of Nebraska at Kearney Grant and a scholarship from the Spanish Ministry of Education and Science.
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