SUNDAY, May 13, 2007 (HealthDay News) -- Whether America's fast-food-and-video-game culture, or some other confluence of factors is to blame, there's no denying that adolescents' health is at risk.

Little wonder, then, that one group of researchers has begun to take a serious look at the long-term health consequences of kids' inactivity. And they are using cholesterol levels as a window into these youngsters' futures.

Obesity, inactivity and cholesterol are closely linked, and data from the latest U.S. National Health and Nutrition Examination Survey (NHANES) finds that 17 percent of U.S. teens are overweight. Just one in four high school students packs enough physical activity into their day, and 12 percent get little or no daily exercise, reports the U.S. Centers for Disease Control and Prevention.

So, measuring kids' cholesterol in a really detailed way may make sense.

"There is growing scientific evidence indicating that cholesterol levels in childhood and adolescence have an effect on the development of plaque in the arteries, which is a clear indication of cardiovascular disease risk," explained study leader Ian Janssen, an assistant professor in the School of Kinesiology and Health Studies at Queens University in Ontario, Canada.

"There is also strong evidence indicating that children and youth with high cholesterol will continue to have high cholesterol in adulthood," he added. "Thus, it is important to start treatment and prevention efforts early."

Using data from the NHANES on more than 6,000 kids aged 12 to 20, Janssen and his colleagues developed age- and gender-specific reference points for total cholesterol, LDL ("bad") cholesterol, HDL ("good) cholesterol and triglyceride fat levels. The new tables, published last year in the journal Circulation, take into account fluctuations in cholesterol and fat that occur as a child matures.

The new reference data are meant to improve upon current guidelines, published by the U.S. National Cholesterol Education Program, which do not account for age-related fluctuations.

Still, Janssen admits that the guidelines have not yet been routinely adapted into clinical care settings in the United States. "These sorts of changes to clinical practice typically take years to manifest," he said.

Dr. Marc S. Jacobson, director of the Center for Atherosclerosis Prevention at Schneider Children's Hospital in New Hyde Park, N.Y., said it's unclear how the new tables will be received in the United States.

"It complicates lives of people like me who treat adolescents with lipid problems because instead of just having one number, you have to have four graphs and plot them out by age," he said.

"Instead of having one cut point," he continued, "you have a graph that you have to plot out a percentile. With each lipid profile, you have to decide which percentile this is for that individual's age. And when it goes up and when it goes down, did it go down because of treatment? Or did it go down because of advancing puberty?"

The challenge, then, is to make sense of that information, he explained. "It argues that you almost have to take it into account because you could say if the LDL changes, is it the treatment or is it a change in puberty?"

Currently, the federal government recommends cholesterol screening for children and teens with at least one parent with high cholesterol or a family history of early heart disease.

"Typically high-risk adolescents should be screened, and probably every year or two," Janssen said. "A high-risk adolescent would be one who's had a parent or grandparent with premature cardiovascular disease or high cholesterol, or a teen with other risk factors, such as obesity and high blood pressure."

Other risk factors, such as high blood pressure, obesity, diabetes or smoking, also would trigger cholesterol testing in doctors' offices, "and that covers a lot of kids now," Jacobson noted.

The issue is destined to garner greater attention when a U.S. National Heart, Lung, and Blood Institute (NHLBI) panel updates guidelines on cholesterol screening in children and teens. The new guidance is scheduled for release in April 2008, said Dr. Rae-Ellen Kavey, senior medical officer with the Pediatric Cardiovascular Risk Reduction Program in NHLBI's Office of Prevention, Education, and Control.

"Stay tuned," Kavey said, "because there really is going to be new information."

More information

Find out more about cholesterol at the U.S. National Heart, Lung, and Blood Institute.

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