TUESDAY, Aug. 7, 2012 (HealthDay News) -- Cholesterol levels among U.S. kids have improved in recent decades, but almost one in 10 still has high total cholesterol, which endangers their heart health, U.S. health officials report in a new study.
The study included more than 16,000 children and teenagers aged 6 to 19 years who took part in the U.S. National Health and Nutrition Examination Surveys during three periods -- 1988-1994, 1999-2002 and 2007-2010. Overall, average total cholesterol levels decreased slightly, but more than 8 percent had elevated total cholesterol in 2007-2010.
Although researchers can't say precisely what led to the overall improvement, several lifestyle factors likely play a role. But experts also caution that many children remain at risk for heart disease.
"We know that dietary intake of saturated fat and trans fats and exposure to second-hand smoke are related to blood cholesterol, so changes aimed at limiting these may have contributed to the changes that we observed," said study author Dr. Brian Kit, a pediatrician and epidemiologist at the U.S. Centers for Disease Control and Prevention in Hyattsville, Md.
As a result of the current U.S. childhood obesity epidemic, conditions formerly seen only in adults, such as high blood pressure, type 2 diabetes and high cholesterol, are increasingly observed in children. But the decline in cholesterol held even in the face of obesity increases noted during the study, Kit said.
The study, published Aug. 8 in the Journal of the American Medical Association, found that 22 percent of children aged 9 to 11 years had either low levels of high-density lipoprotein (HDL), the "good" cholesterol, or high non-HDL cholesterol concentrations in 2007-2010 -- down from about 27 percent two decades earlier. The latter refers to the difference between the total cholesterol concentration and the good or HDL cholesterol concentration.
Average total blood cholesterol decreased from 165 milligrams per deciliter of blood (mg/dL) in 1988-1994 to 160 mg/dL in 2007-2010, the study showed. HDL cholesterol rose from 50.5 mg/dL in 1988-1994 to 52.2 mg/dL in 2007-2010.
And high total LDL cholesterol, noted in 11.3 percent of youths in 1988-1994, declined to 8.1 percent in the most recent time frame.
Dr. Sarah de Ferranti, director of preventive cardiology at Boston Children's Hospital, said "these small gains are important, but we have a lot of work to do in the weight area.
"The study is a mixed bag," de Ferranti said. "There is some good news in that cholesterol values are getting better, good cholesterol is getting higher and bad cholesterol and triglycerides are coming down, so all of the numbers are going in the direction that I would like."
Still, "I am concerned that small gains are going to be dwarfed by the effects of excess weight and pediatric obesity," she said. "We are not out of the woods.
It's estimated that almost 17 percent of U.S. youth -- or about 12.5 million kids ages 2 to 19 years old -- are obese.
Controlling cholesterol and weight are key strategies in the war against heart disease. Atherosclerosis -- the buildup of plaque inside blood vessels -- starts in childhood and is linked to high levels of LDL or "bad" cholesterol, low levels of HDL cholesterol and other unfavorable levels of blood fats.
Concerned parents should know their own cholesterol numbers and be aware of their family history of high cholesterol and heart disease, de Ferranti said.
"Current guidelines suggest specific time points for screening cholesterol levels in children," she said. The U.S. National Heart, Lung, and Blood Institute recommends all children be screened for high cholesterol at least once between the ages of 9 and 11 years and again between ages 17 and 21. "But, if a child has particular risk including obesity, he or she can be screened at any time after age 2," de Ferranti said.
Dr. Michael Pettei, chief of nutrition at Cohen Children's Medical Center of New York in New Hyde Park, N.Y., said following the recommended screening schedule is critical. "Despite the improvements, the recent recommendations . . . for universal lipid screening of children aged 9 to 11 years is still quite valid to find the individuals at the most extreme risk, particularly from the genetic [blood fat abnormalities]," he said.
He termed the CDC findings "intriguing," especially since the "slight improvement" coincides with the obesity epidemic in the same age groups. "It thus becomes more important for an eventual analysis of the dietary and exercise factors associated with the noted improvements," Pettei said.
The Nemours Foundation talks about cholesterol to kids.