By Amy Norton NEW YORK (Reuters Health) - The percentage of U.S. teenagers with "pre-diabetes" or full-blown type 2 diabetes has more than doubled in recent years -- though obesity and other heart risk factors have held steady, government researchers reported Monday.
The good news, the researchers say, is that teen obesity rates leveled off between 1999 and 2008 -- hovering between 18 percent and 20 percent over the years.
Rates of high blood pressure and high LDL cholesterol (the "bad" kind) also remained steady.
But the picture was different with so-called pre-diabetes and with type 2 diabetes. Those conditions were seen in nine percent of teens in 1999-2000, but that figure rose to 23 percent in 2007-2008, the researchers report in the journal Pediatrics.
"That was unexpected, especially since obesity has been leveling off," said lead researcher Ashleigh May, of the Centers for Disease Control and Prevention (CDC).
"The question of why that is will require more research," May told Reuters Health.
Pre-diabetes refers to higher-than-normal blood sugar levels. It's concerning, May said, because people with pre-diabetes have a heightened risk of developing type 2 diabetes, which is a major risk factor for heart disease, stroke and kidney disease.
This study did not separate pre-diabetes from type 2 diabetes, so it's not clear how much of the rise was in full-blown diabetes, May said.
But in the past the CDC has estimated that between 2002 and 2005, the yearly rate of new type 2 diabetes diagnoses was 8.5 for every 100,000 kids ages 10 to 19.
Type 2 diabetes is closely associated with age, and middle-aged and older adults still account for most cases. In the U.S., it's estimated that almost 26 million people have diabetes -- mostly type 2. Adults age 65 and up account for about 11 million of those cases.
At one time, type 2 diabetes was almost unheard of in children. But with the rise in childhood obesity in recent decades, more kids have been diagnosed with that form of diabetes, or its potential precursor pre-diabetes.
Unhealthy blood sugar levels -- or blood pressure or cholesterol levels -- may not affect a teenager right away. But the concern, May noted, is that those things tend to "track" into adulthood, when they may contribute to heart attacks or stroke.
"It's promising that we didn't see a rise in obesity or hypertension or (high LDL)," May said. "But we still have a lot of work to do."
The results are based on a national sample of almost 3,400 teenagers who had physical exams and blood tests between 1999 and 2008.
Rates of obesity remained stable over the years, landing at 20 percent by 2008. Another 15 percent of kids were overweight.
By 2008, 10 percent of teens had "pre-hypertension" -- which means their blood pressure numbers were higher-than-normal, but not high enough to meet the definition of hypertension. Another three percent had full-blown high blood pressure.
When it came to LDL cholesterol, six percent of teens had high levels and 13 percent were borderline-high in 2008.
Those figures were similar to the ones almost a decade earlier. Pre-diabetes/diabetes was the exception.
There are limitations to the study, May's team acknowledges. One is that they gauged pre-diabetes and diabetes from a single blood sugar measurement -- which may be less reliable in kids than in adults.
Still, May said the "big message" here is that children and teenagers need more help with following a healthy diet and staying physically active.
That's the general way of managing pre-diabetes, May said, and it's also the key to overall health, for both heavy and normal-weight kids.
In this study, pre-diabetes/diabetes and other heart risk factors were more common in overweight or obese teens. But their normal-weight peers were far from immune.
Of those thinner kids, 37 percent had at least one heart risk factor, May pointed out.
"All kids can benefit from a healthy lifestyle," May said.
For parents, she said, that means "modeling" healthy eating and exercise for their kids, and making sure the kitchen is stocked with foods like fruits, vegetables, whole grains and low-fat dairy -- rather than junk food.
May also said that pediatricians should be following guidelines on obesity screening.
The U.S. Preventive Services Task Force, a government-backed panel, recommends that children age six and older be screened for obesity. If a child is heavy, pediatricians should offer families behavioral counseling, or refer them to someone who can.
The American Academy of Pediatrics (AAP) recommends that children have their blood pressure checked regularly starting around age four. The AAP also suggests that kids' cholesterol be checked between the ages of nine and 11, and then again between the ages of 17 and 21.
SOURCE: Pediatrics, online May 21, 2012.