CHICAGO Watching too much television may not only help make children fat, it may also raise their blood pressure, U.S. researchers said on Tuesday.
They found obese children who watched four or more hours of TV a day were three times more likely to have high blood pressure than children who watched less than two hours a day.
"There is a significant association between hours of television watched and both the severity of obesity and the presence of hypertension in obese children," Dr. Jeffrey Schwimmer of the University of California, San Diego and colleagues wrote in the American Journal of Preventive Medicine.
Many studies have found a strong link between watching TV and obesity, but this is the first study to show a link between TV and blood pressure in obese children and teens, the researchers wrote.
Obesity in children is on the rise, increasing the risk of heart disease and diabetes. And high blood pressure in children has been rising in right along with obesity rates.
The problem is often undiagnosed in children, and if undetected, high blood pressure can quietly damage the organs, especially the kidneys.
Schwimmer worked with researchers at the University of California, San Francisco, and the University of South Alabama. They studied 546 children and teens aged 4 to 17 seen at weight management clinics from 2003 to 2005.
Height and weight were measured to determine a body mass index, or BMI, and blood pressure was recorded.
Children were considered obese if their BMI measures were above the 95th percentile for age and gender. Children in the study had a mean BMI of 35.5. In adults, a BMI of 30 or higher is considered obese.
The children and their parents estimated how much time they spent watching TV, and a doctor reviewed and confirmed their estimates.
The researchers found children who watched two to four hours of TV were 2.5 times more likely to have high blood pressure compared with those who watched less than two hours of television a day. Those who watched more than 4 hours per day were 3.3 times more likely to have hypertension.
The authors said the study illustrates the need for parents to curb their children's TV time, especially for children who are already obese or have high blood pressure.
The American Academy of Pediatrics recommends children watch fewer than two hours of TV per day.
Some 17 percent of U.S. children are obese, according to the U.S. Centers for Disease Control and Prevention.