BMI and Blood Pressure in Kids
High blood pressure isn't just for adults anymore. Today's epidemic levels of obesity and extra weight among kids make it a real concern for the younger set. In the last three decades, hypertension rates shot up from one percent to five percent among those under 18 years of age. And some researchers believe that the first signs of atherosclerosis can be found in four-year-olds. So the recent work of researchers at Regenstrief Institute in Indianapolis, led by Wanzhu Tu, PhD, is of great importance. The researchers showed that small reductions in a child's body mass index (BMI) were likely to yield big improvements in blood pressure for overweight kids.
A 2007 study estimated that as many as one in twenty American teens may have high blood pressure. The researchers studied the health checkup records of 14,000 children between the ages of three and 18. Of 507 kids who had high blood pressure; only 136 were diagnosed as such in their medical records (we'll talk more about that in a moment). Responding to the study, UK professor Francesco Cappuccio, of the University of Warwick, said there is "an evolving epidemic of hypertension in youth, which is closely associated with a parallel epidemic of obesity." He added that, "by the age of 40 many of today's teenagers could need multi-drug treatment, as the effects of high blood pressure hit home."
As we mentioned above, many doctors have ignored high blood pressure in children, either because they didn't have time to confirm the diagnosis -- it takes three consecutive readings -- or because, in kids, the criteria vary by age, sex, and percentile for height, so recognizing high blood pressure is not as straightforward. Recognized or not, the impact of high blood pressure can be significant. A child who spends many years with undetected high blood pressure is a candidate for "end-organ damage" that is, in the major organs fed by the circulatory system, which include the heart, brain, eyes, and kidneys.
In the Regenstreif Institute study, the researchers looked at 1,113 kids, following their weight, height, and BP over time. Some of the kids were studied for more than ten years. Then, they compared the BMI of these kids to national data, which was adjusted for age, sex, and height. The researchers found that up until the overweight range was reached (BMIs under the 85th percentile), BMI had very little effect on blood pressure. But once the overweight threshold was reached (BMIs higher than the 85th percentile), a very strong connection between BMI and blood pressure levels was found, especially if the BMI was at or above the 90th percentile. The correlation was so strong that even small BMI increases led to large increases in blood pressure. For overweight boys, the impact of their BMI on systolic blood pressure -- the bottom number in blood pressure, which measures the force of the blood against the arteries when the heart is contracted -- was 4.6 times that of normal boys.
Said study co-author Wanzu Tu, "Because our estimate of the BMI effect was much greater in overweight kids, the results suggest that even a modest reduction in BMI may produce a much greater benefit in blood pressure in overweight kids. Conversely, a small increase in BMI could put them at much greater risk of blood pressure elevation."
This reinforces what we already know. Obese and overweight kids need to shed pounds to avoid all kinds of unpleasant consequences, including developing cardiovascular disease and Type II diabetes. And while it's easy to prescribe more physical activity and less junk food for kids, it's not so easy to get them to comply with that prescription. The lure of sedentary activity fueled by carbs, sweets, and fats is overwhelming in our society. Still, a study published in the December 2009 American Journal of the American College of Cardiology showed that if obese kids exercised regularly, after just three months they would achieve significant reductions in their blood pressure and significant improvements in their artery health.
Meanwhile, a Geneva study showed that when overweight kids exercised for 60 minutes three times each week, within three months they achieved significant BP reductions without dieting. The exercise also seemed to help them slightly reduce their intake of calories. According to the director of that study, Dr. Nathalie Farpour-Lambert of the University Hospitals of Geneva, "What's new about this study is that we did an intervention in really young kids, with an average age of just under nine, and we didn't talk about food or nutrition at all." The 44 children played ball, swam, ran, and participated in other "fun" activities, and the program had no dropouts. After six months, the prevalence of hypertension had gone down by 29 percent in the study group. As a result, the researchers recommended that overweight kids be encouraged to play and exercise rather than being put on diets.
Given these study results, it's a sad fact that so many public schools nationwide have reduced or completely eliminated physical education programs in schools because of budget cuts. The 30 minutes a day that children might spend in a gym class could, theoretically, add 30 years of good health to their lives. But it doesn't look like the funding for mandatory physical fitness programs in schools is going to reappear anytime soon, so in the interim, make sure your kids stay active and of course, if you can minimize their intake of junk food, you'll hopefully prevent preventable problems like hypertension. And as I just mentioned in a previous blog, one possible answer may lie in the new generation of Wii and X-box video games that require a high degree of total body physical interaction.