Study: Inactive Kids Face 6-Fold Risk of Heart Disease by Teen Years

April 2008 - Young children who lead inactive lifestyles are five-to-six times more likely to be at serious risk of heart disease, with that degree of danger emerging as early as their teenage years, according to a new study by researchers at the University of North Carolina at Chapel Hill.

The findings, published Friday (April 4) in the open access journal Dynamic Medicine, looked at a group of children twice first while in grade school, then again seven years later when they were in their teens.

Researchers wanted to know more about the early onset of metabolic syndrome, a condition more commonly found in adults. Metabolic syndrome is the label given to a clustering of medical disorders that raise the risk of heart disease and diabetes, such as glucose intolerance, hypertension, elevated triglycerides, low HDL (so-called "good") cholesterol and obesity. Previous studies have found that somewhere from four percent to nine percent of adolescents have the condition.

However, until now, no one had tracked the same group of children over time to see just how fitness and activity levels in their early years played a role in the likelihood of them developing metabolic syndrome by the time they were teenagers, said Robert McMurray, professor of exercise and sports science in the department of exercise and sports science in UNC's College of Arts and Sciences.

The study looked at data from almost 400 children between the ages of seven and 10 from across North Carolina. Researchers measured factors such as height, body mass, percentage body fat, blood pressure and cholesterol levels. Participants were also surveyed about their physical activity and given an aerobic fitness test.

When the same children were examined again seven years later, 4.6 percent had three or more characteristics of metabolic syndrome.

McMurray said adolescents with the syndrome were six times more likely to have had low aerobic fitness as children and five times more likely to have low levels of physical activity at the time they joined the study.

For example, as children, those who had low levels of physical activity got no vigorous exercise (such as playing basketball or soccer) and spent less than 20 minutes a day doing moderate-intensity physical activity (walking briskly, riding a bike at a medium speed). That means that at best, they were getting just one-third of the 60 minutes a day that is currently recommended for children by the Centers for Disease Control and Prevention, said McMurray.

"This shows efforts need to begin early in childhood to increase exercise," he said. "Children today live a very sedentary life and are prone to obesity. This is the first study to examine the importance of childhood fitness levels on your metabolism as a teenager. Previously we didn't know if low fitness levels were an influence.

"It's obvious now that there is a link and this is something which we need to pay attention to by encouraging our kids to keep fit, or suffer the consequences later in life," said McMurray.

McMurray also holds professorships in physical therapy in the department of exercise and sports science, and in the School of Public Health's nutrition department. In addition, he coordinates the master of arts specialization in exercise physiology. Other authors of the study were Shrikant I. Bangdiwala, research professor in the UNC School of Public Health's biostatistics department; Joanne S. Harrell, the Frances Fox Hill professor in the School of Nursing and director of the Center for Research on Chronic Illness; and Leila D. Amorim, who at the time the paper was written was a graduate student in the School of Public Health's biostatistics department and is now an assistant professor in the statistics department at the Federal University of Bahia in Salvador, Brazil. The study, titled "Adolescents with metabolic syndrome have a history of low aerobic fitness and physical activity levels," can be found at http://www.dynamic-med.com.

Source: University of North Carolina at Chapel Hill