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Is Hypertension in Children Increasing?

September 02, 2009

Hypertension, or high blood pressure, in children and adolescents appears to be increasing. Why? How serious is hypertension in children, how is it treated and what can it lead to if not treated? What can parents do? Hopkins Children’s nephrologist Tammy Brady answers some of the questions. 

So, is hypertension in children increasing? 

It is. In the 1970s and 1980s, just over 1 percent of children showed evidence of high blood pressure (BP); today that number is 5 percent. The obesity epidemic is one possible explanation, because about 30 percent of obese children have hypertension. And we know the prevalence of hypertension in children increases with the increasing BMI (body mass index) percentile. But thanks to public health studies there’s also a greater awareness of the condition by pediatricians, which has led to an increase in detection.

How does obesity contribute to hypertension?
We’re not exactly sure but we do know obesity is related to inflammatory conditions that lead to problems with blood vessels. But childhood hypertension is not always related to obesity. In fact, for children up to age 12, more often it’s going to be related to some secondary cause like a history of urinary tract infections or an underlying heart or kidney problem. Once we get into the teenage and young adult years we see more of the essential or primary hypertension we see in adults, though secondary causes are still seen in up to 15 percent of 12-to-18 year-olds.

Are pediatricians picking up hypertension in their patients?
In trying to determine what impacts recognition of elevated blood pressure among children in a general pediatric clinic, we found that the more overweight and obese a child is, the more likely their elevation will be recognized. Having a reading above 120/80 also led to improved recognition of elevated levels. Also, children with a systolic BP of 120 mmHg or greater were eight times more likely to have their blood pressure recognized than children with a blood pressure reading less than this value. And having a family history of cardiovascular disease led to increased recognition by providers. But the rate of recognition of elevated blood pressure overall is pretty poor, even in obese patients, with only 22 percent having their elevated blood pressure picked up.

Why is that?
Well, that’s hard to say. Because normal blood pressure in childhood varies with age and height, there are many steps involved in determining whether a child has an elevated blood pressure. The pediatrician must first measure and plot child’s height on a growth curve, and then refer to a table with that height percentile and the child’s age to determine if the blood pressure is elevated. That can take a lot of time, and may explain why the more obvious blood pressures of 120/80 or higher are more recognized. Also, pediatricians tend to use digital monitors, which don’t actually measure blood pressure but estimate it. These machines are designed to inflate to the pressure level of the previous patient and then add 30 millimeters of mercury. So you could have a systolic reading of 90 for a three-year-old who is followed by an obese adolescent with an actual systolic pressure of 150. The cuff will only inflate to 120 mmHg, and the child’s true blood pressure of 150 mmHg will never be captured.  And, of course, the pediatrician says “Great,” but misses his real blood pressure.

What are the guidelines for screening for hypertension?
All patients three years of age or older – or under three but with a history of prematurity, low birth weight, congenital heart disease or kidney disease – should have their blood pressure checked at each visit. If you’re using a machine, you have to take three readings, then disregard the first and average the second two readings. If the average reading is high and you want to determine whether it’s a truly sustained elevation due to hypertension, the blood pressure should be rechecked twice manually with the pediatrician using a stethoscope. If still elevated, do two more readings over two visits. But this is rarely done. Nonetheless, if after three visits the average reading is over the 95th percentile, you have a diagnosis of hypertension.

What should parents look for?
There are rarely extreme symptoms like bloody nose, headache, nausea and vomiting, which need to be attended to immediately if they’re indeed related to hypertension. But in most cases there are no signs, which is why parents are often surprised to learn their child has hypertension. Often times these are family members who have hypertension themselves.

How do parents react when you tell them their child has hypertension?
Again, they’re surprised. The child appears and acts healthy, so what’s the problem? Many don’t buy into it.

How do we treat hypertension in children?
The biggest thing is to treat it early because we’ve seen how hypertension in obese children clusters with other conditions like hyperlipidemia, Insulin resistance and Type 2 diabetes mellitus. All children should be encouraged to have at least 30 minutes of activity a day, and to limit their sedentary activities to less than 2 hours a day. That’s really hard in this era of video games. They should also try to eat more fruits and dairy, limit their salt intake and avoid fast food. Some children have to go on medications, but the good news is these medications can bring blood pressure down, improve the child’s overall health and decrease his risk of cardiovascular disease and LVH.

About 40 percent of hypertensive children will have a thickening of their heart due to the high blood pressure, a condition called LVH or left ventricular hypertrophy. I explain to families that if I’m lifting weights for a long time my arm muscles are going to get big. Similarly, if the heart, which is a muscle, pumps for a period of time against a higher pressure, it’s only natural that it will get thicker. Once you decrease that pressure, then the heart no longer has to work as hard and can get back to its normal size. LVH is present in up to 41 percent of children and adolescents with mild, untreated blood pressure elevation, and it can develop relatively quickly, placing them at risk of arrhythmias, heart attacks, stroke and an early death as adults. That’s why all children who have hypertension should have an echocardiogram to look for signs of LVH when they’re getting worked up.

Do sleep apnea and ADHD meds play a role?
We need to screen for sleep apnea because if it’s present and we don’t treat it, we’re going to have a hard time getting the blood pressure back to a normal range no matter what medicines we use. For some kids the hypertension goes away once they have their tonsils removed or when they’re prescribed CPAP (continuous positive airflow pressure) therapy. Regarding ADHD medications, some pediatricians cease them when the patient shows signs of high blood pressure. But, studies have shown, the contribution of ADHD meds to hypertension has been minimal.

Any closing thoughts?
We know that if high blood pressure is treated appropriately you can reverse the heart thickening that may be present, which decreases a child’s cardiovascular risk. We also know that the simple lifestyle modifications I described earlier are very effective in normalizing blood pressure. Children who were once on medications can come off of them. But early diagnosis and treatment of hypertension are essential in protecting the cardiovascular health of our children.