Researchers from the University of California, San Diego; the Rady Children's Hospital, San Diego; the University of California, San Francisco; and the University of South Alabama have determined that television viewing is not only linked to childhood obesity, but also to hypertension in children. The result of the study was published in the December 2007 issue of the American Journal of Preventive Medicine.
Childhood obesity is a major health concern in the United States. As of 2004, the National Health and Nutrition Examination Survey (NHANES) estimated that 17% of children and adolescents were obese. Obesity is known to increase the possibility of cardiovascular risk factors, such as hypertension. Recent studies have shown that cardiovascular risk factors in childhood are significant predictors of preclinical atherosclerosis in adulthood.
Data was gathered regarding 546 subjects, aged 4 to 17 years, who were evaluated for obesity at pediatric subspecialty weight management clinics in San Diego CA, San Francisco CA, and Dayton, OH, from 2003 to 2005. Children and their parent(s) were given a written questionnaire, which was used to estimate the average daily time spent watching TV, and then a physician verbally reviewed and confirmed the time estimate. The height and weight of the children were measured to determine a Body Mass Index (BMI) and their blood pressures were recorded.
Investigators determined that TV time was positively correlated with the severity of obesity. After controlling for race, site, and BMI score, both the severity of obesity and daily TV time were significant independent predictors of the presence of hypertension. Children watching 2 to 4 hours of TV had 2.5 times the odds of hypertension compared with children watching 0 to <2 hours. The odds of hypertension for children watching 4 or more hours of TV were 3.3 times greater than for children watching 0 to <2 hours of TV.
Writing in the article, Jeffrey B. Schwimmer, MD (Associate Professor of Pediatrics at University of California, San Diego and Director of Weight and Wellness at Rady Children's Hospital - San Diego), states, "The current study illustrates the need for considerable physician and family involvement to decrease TV time among obese children. The American Academy of Pediatrics (AAP) recommends that children watch less than 2 hours of TV per day, but reports that only half (51%) of pediatricians make this recommendation to patients...TV viewing is an attractive target for intervention, particularly among obese children with hypertension. Several studies have demonstrated that changing TV time alone can lead to weight loss, without any changes in physical activity."
In a commentary published in the same issue of the American Journal of Preventive Medicine, Stuart J.H. Biddle, from the School of Sport and Exercise Sciences, Loughborough University, UK, cautions that studies of TV viewing are part of a recent trend to study sedentary behaviors in general, and such studies are difficult to interpret.
He argues, "There is much debate concerning whether TV viewing is associated with obesity in young people...For example, an extensive meta-analysis of mainly cross-sectional studies showed that the relationship is very small...Moreover, the small relationship may be a reflection of other trends...If obesity is causally related to TV viewing, as some suggest, how do we account for the following paradoxes: (1) obesity levels are increasing but TV viewing figures are not, (2) obesity increases during adolescence at the same time that TV viewing decreases, and (3) boys watch more TV than girls but show less obesity and greater physical activity" Whatever the true findings, the association between sedentary behavior (TV viewing or other behaviors) and health outcomes, at least in youth, is likely to be complex and, as yet, unknown."