CV Risk in Teens: Putting It in Perspective

Joseph A. Skelton, MD, MS

May 22, 2012

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I am Dr. Joseph Skelton. I am Assistant Professor of Pediatrics at Wake Forest Baptist Medical Center, and I'm Director of the Obesity Treatment and Research Center here at Brenner Children's Hospital in Winston Salem, North Carolina.

I'm here today to talk about a new study that just came out in Pediatrics, called "Prevalence of Cardiovascular Disease Risk Factors Among US Adolescents: 1999-2008."[1] (Read Medscape Medical News coverage of this study.) This study is by May, Kuklina, and Yoon, who used National Health and Nutrition Examination Survey (NHANES) data. NHANES is a well-conducted, cross-sectional study that is continuous, and it releases data every 2 years.

The researchers used data from adolescents 12-18 years of age and looked at 4 cardiovascular disease (CVD) risk factors: prehypertension or hypertension; a high LDL cholesterol (LDL-C); a low HDL cholesterol (HDL-C); and prediabetes or diabetes. The study really focused on the prediabetes and diabetes findings, which I'll talk more about in a minute.

The main finding that was sort of shocking, which we all know, is that adolescents are carrying a significant risk for future cardiovascular disease. In particular, the study highlighted that even normal-weight children carried at least 1 CVD risk factor. In fact, 37% of children who were of normal weight had at least 1 CVD risk factor. Of course, as weight went up, those risk factors started to increase. Some overweight and obese children had upwards of 4 CVD risk factors, which is 1 in each of the categories that I spoke about.

The other interesting finding from the study -- and this goes with other NHANES studies that have been released over the past few years -- is that from 2000 up until 2008, it seems that the prevalence of obesity has somewhat plateaued to somewhere around 16%-18%. CVD risk factors of prehypertension and hypertension, high LDL-C, and low HDL-C also somewhat plateaued. In fact, the prevalence of low HDL-C actually decreased somewhat, while prehypertension and hypertension and high or borderline high LDL-C plateaued, consistent with the plateauing in obesity prevalence.

One of the surprising findings from this study was that even though obesity prevalence plateaued from 1999 to 2008, the prevalence of prediabetes or diabetes actually increased, and it increased quite significantly from 9% to 21% across the whole population, and not just in those teens who were overweight or obese. So, that's a really significant increase in the prevalence of prediabetes and diabetes.

Now, what does this mean? Well, there is a lot behind this, and I may note these limitations in the study. The researchers defined prediabetes or diabetes by a single fasting glucose. Prediabetes is defined in adults and children as a fasting plasma glucose between 100 and 125 mg/dL. It previously was defined as a glucose of 110-125 mg/dL. The threshold was lowered in 2003 to better capture some of those people with early signs of insulin resistance or diabetes.

There is also some language in the paper that needs to be clarified a little bit. The terms "prediabetes" and "at risk for future diabetes" are sort of the same (and the authors note that in the article), consistent with terminology used in the American Diabetes Association recommendations. When explaining the results of a fasting glucose to families or to parents, you have to check what sort of language you are using, because if you are telling someone that their child has prediabetes, often that can elicit fear; families may not understand what that term means, especially if there is a strong history of diabetes.

Scaring families is not really the best method to instigate change because, really, what you want to do is report the increased risk to the family but also talk with them about some changes they can make to improve their health and their child's health. What needs to be explained, from the scientific standpoint, is that a fasting glucose of 100-125 mg/dL probably means that the child is at high risk for diabetes later.

Another change that is on the horizon that is important for practitioners to learn is that, in adults, hemoglobin A1c (A1c) is also used to diagnose diabetes and prediabetes. The oral glucose tolerance test and the fasting plasma glucose were the only diagnostic tests in the past. Now there are very strong data in adults showing that prediabetes is probably defined by a 5.7% A1c up to a 6.4% A1c.

An A1c of 5.6% is about the same as a fasting glucose of 110 mg/dL; an A1c of 5.4% is equivalent to a fasting glucose of 100 mg/dL. So, there is a lot of difference between 100 and 110 mg/dL. From a practical standpoint, in the patients we see in our program and in our clinic, we have a lot of children with a fasting glucose in the 100 to 105-110 mg/dL range. In those children, we obtain an oral glucose tolerance test and a repeat fasting glucose, and they are typically all normal.

By lowering the lower edge of that cutpoint to 100 mg/dL, there are going to be a lot of children who probably have normal glucose tolerance and may not necessarily have the same risk for diabetes as a child with a fasting glucose of 120 mg/dL. In children, we are still trying to figure a lot of this out, but we all still agree that by lowering the cutoff for fasting blood glucose, the main point is to identify those children at risk for future diabetes and to share that information with families in an effective manner.

So, in the end, the study really covers a lot of what we have known over the past several cycles of the NHANES data and what we see both in our clinical practices and in the research: Even though obesity is still a significant health problem in the United States, the prevalence is plateauing, at least in the population of adolescents. Despite this plateauing, teenagers have significant CVD risk factors, in particular an increase in the prevalence of prediabetes and diabetes, for unknown reasons.

We are not really sure how to explain that, but it does seem to be a real finding, though there may be other influences -- either diet alone or activity alone. Despite a lot of the efforts that we have made in the awareness and prevention of obesity, there still seems to be something going on in these children, in particular those normal-weight children who also carry CVD risk factors. For the primary care practitioner, these data send a message that, even in those children who are at low risk for CVD and maybe even for obesity, we still need to focus on healthy habits.

One third of our children are overweight or obese; two thirds of adults are overweight or obese. So, that's one third of these children who are likely going to develop a weight problem as they grow older. Now is the time -- when they don't have a weight problem -- to begin these preventive measures.

I hope this has been helpful. I encourage you to read this article. I think it's very interesting and is bringing more into the discussion of prediabetes, how to use these new guidelines, and possibly preparing us for, in the future, being able to use hemoglobin A1c as a screening tool in addition to a fasting glucose. Thank you for your time.


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