While unchecked cholesterol may spell trouble for adults, the picture is less clear for kids, whose cholesterol levels often change as they grow up.

In a study out this week, Australian researchers say certain lifestyle choices could help explain why some kids with troubling cholesterol levels stay at risk and others don't.

They found youths with high-risk cholesterol whose waistlines grew more, or who began or continued to smoke, were more likely to stay at risk as adults than those who added fewer pounds or dropped the cigarettes.

"This is useful from a clinical perspective," said Dr. Stephen R. Daniels, pediatrician-in-chief at Denver Children's Hospital, who was not involved in the study. "These are things we should be able to improve, like cigarette smoking and physical activity."

The importance of cholesterol levels in children isn't clear, but in adults high levels of LDL or "bad" cholesterol, as well as low levels of HDL or "good" cholesterol, up the risk of heart disease, a major killer in Western countries.

Millions of adults use cholesterol-lowering statins, but doctors still argue about whether kids would also benefit from the drugs.

The American Academy of Pediatrics recommends considering drug treatment when LDL cholesterol rises to at least 190 milligrams per deciliter (mg/dL). If a parent or grandparent has heart disease or high cholesterol, the threshold is 160 mg/dL.

On the other hand, the U.S. Preventive Services Task Force, a federal expert panel, says there is no evidence that putting kids on statins will prevent heart disease decades later. And recent research hints some kids' cholesterol may drop naturally over time.

The new findings, published in the Archives of Pediatrics and Adolescent Medicine, are based on 539 Australian school children, aged seven to 15, who had blood drawn in 1985 and again 20 years later. Both cholesterol and the so-called triglycerides, the building blocks of fat, were measured.

On both occasions, the participants also did a bicycle fitness test and answered questions about smoking, education and food intake.

As adults, 12 percent of the participants overall had low HDL cholesterol, a risk factor for heart disease, compared to 26 percent among those who didn't improve on any lifestyle factor between the two tests.

Many of the adults who'd had high-risk levels of cholesterol and triglycerides as kids no longer did at the follow-up test, while others with healthy levels as children developed risky ones along the way. For example, less than half of the adults with high total cholesterol had the problem as kids (12 men and seven women).

As a result, Costan Magnussen of the University of Tasmania in Hobart and the University of Turku in Finland and colleagues write, weight control and other prevention efforts may be a good idea, even for kids without high-risk cholesterol.

That advice is echoed by Daniels. "I think the hard part is changing behavior," he said, adding that avoiding becoming overweight, smoking and eating bad food in the first place was the better way.

"The message is one of prevention," he told Reuters Health.

Source: bit.ly/igIfPs Archives of Pediatrics and Adolescent Medicine, online January 3, 2011.