"The risk was about 1.6 times higher for girls than for boys," said Dr. Joanne S. Harrell, professor of nursing and director of the Center for Research on Chronic Illness at the UNC School of Nursing. "I want to alert people to the potential dangers and motivate them to help our youth increase physical activity and avoid obesity."
Harrell, the lead researcher, reported her group's findings Sunday (Nov. 9) at an American Heart Association scientific meeting in Orlando, Fla. Co-authors are Dr. Robert G. McMurray, professor of exercise and sport science in the College of Arts and Sciences; research assistant Leila Amorim and project manager Dana Creighton, both of nursing; and Dr. Shrikant I. Bangdiwala, research professor of biostatistics at the School of Public Health.
Metabolic syndrome consists of the heart disease risk factors high blood pressure, elevated triglycerides, lower-than-average high-density lipoprotein (HDL, or "good" cholesterol) levels, glucose intolerance, elevated insulin and excess weight. The syndrome boosts the risk of diabetes as well as heart disease.
"These were regular, normal kids, but we found risk factors that are clear danger signs for the future," Harrell said. "If nothing is done, many of these children could develop type 2 diabetes and heart disease."
Investigators examined 3,203 students -- 1,679 girls and 1,524 boys -- between ages 8 and 17. Each lived in a rural N.C. county with no city over 50,000 people. Of the children, 47.9 percent were white, 42.4 percent black and 9.7 percent other races.
Children were evaluated for body mass index, blood pressure, two types of fats in their blood and two indicators of how well they processed glucose. Results reported were based on initial testing of students who will be followed for three to four years.
More than half the participants -- 58.3 percent -- had at least one of the six risk factors, 27.4 percent had two or more and 13.5 percent had three or more, Harrell said.
Some children ages 8 and 9 -- 8.3 percent -- already showed three or more risk factors. Among teenagers 14-17, 11 percent had three or more. The highest rates of multiple risk factors -- 16.2 percent -- were in those entering or about to enter puberty.
The most common risk factor, found in 42.2 percent, was a low HDL level. HDL levels were rated low if they were less than 40 milligrams per deciliter in boys or 50 mg/dL in girls. Researchers also found high triglycerides in 8.6 percent of children.
Triglycerides were deemed high if they were at least 100 mg/dL in children aged 10 or younger or 130 mg/dL in those older than 10.
More than one in four subjects were overweight with a body mass index at or above the 95th percentile for their age, gender and height.
Previously, scientists documented a high level of obesity in teens. The UNC study is looking at the development of six metabolic syndrome risk factors beginning prior to puberty and continuing through the teen years.
"Some insulin resistance is normal with puberty," Harrell said. "In addition, obesity increases with puberty, earlier in girls than in boys. As we follow the children, we'll see whether these factors persist in adolescence."
Significantly more girls -- 16.3 percent -- than boys -- 10.7 percent -- had three or more risk factors, which the researchers attribute to more overweight among girls.
High insulin in the blood -- more than 25 microunits per liter -- was found in 16.1 percent of the children. High blood pressure was detected in 7.7 percent. Children were considered to have high blood pressure if their average systolic or diastolic pressure was at or above the 95th percentile for their gender, age and height on three separate occasions. The least prevalent -- 4.7 percent -- risk factor was glucose intolerance, or prediabetes, marked by a fasting glucose level of at least 110 mg/dL.
"The body tries very hard to keep glucose normal," Harrell said. "Typically, you would have the metabolic syndrome for several years before glucose tolerance becomes impaired."
Follow-up tests of the children may help physicians determine who needs to be screened for various risk factors and at what age, she said. The data reinforce the need for primary prevention of heart disease in youth.
"Greater physical activity can help improve most metabolic syndrome factors, including HDL levels, obesity, high blood pressure and insulin resistance," Harrell said. "Preventing obesity also helps avoid other risk factors."
Note: Harrell can be reached at: (919) 218-3909 (cell), 966-4284 (work, after the meeting ends on Nov. 12) or email@example.com
School of Nursing Contact: Sunny Nelson, (919) 966-1412
News Services Contact: David Williamson, (919) 962-8596
AHA Contacts: Carole Bullock or Julie Del Barto, (407) 685-5402
By DAVID WILLIAMSON
UNC News Services