What can pulse pressure teach us about pediatric obesity?

pulse pressure
Subtract 68 from 100 to get a pulse pressure of 42 (Wikiphoto/Creative Commons)

Second in a two-part series on cardiovascular prevention in children. Read part 1.

Carrying too much weight is tough on the body. The dramatic rise of obesity in recent years means more and more people are confronting increased cardiovascular risk due to changes in their blood vessels, cholesterol levels, blood pressure, and blood sugar. And the problem isn’t limited to adults: Today, there are more than three times as many obese children in the U.S. than there were in the early 1970s.

However, not every person with excess weight has cardiac risk factors, and not everyone with cardiac risk factors carries excess weight. So what is the relationship between childhood obesity and cardiac risk factors later in life? What links excess weight to its consequences?

Justin Zachariah, MD, MPH, a cardiologist at Boston Children’s Hospital, was inspired to investigate these “risk factors of risk factors” when he observed a pattern in his pediatric preventive cardiology clinic. He noticed that many of his patients who were carrying excess weight did not have very high blood pressure, or hypertension. Indeed, other investigators had also noticed that while obesity was skyrocketing across the globe, overall blood pressure was not. Zachariah took this a step further and discovered that in many kids carrying excess weight, the difference between their systolic and diastolic blood pressure (the top and bottom numbers of the blood pressure reading) was very large. This difference, called pulse pressure, predicts future hypertension and cardiac events (i.e., a heart attack, heart failure, or stroke).

Pulse pressure captures three features mainly related to the aorta: size, stiffness and the amount of blood trying to flow through. The size of a blood vessel is related to a person’s height, while the amount of blood flowing through it is related to her weight. If height and weight are out of balance—as they are in a child carrying too much body weight—the aorta will try to expand. At some point, the walls cannot stretch any further and start to stiffen.

In a study published last May, Zachariah and his team examined pulse pressure and obesity rates in the Centers for Disease Control’s National Health and Nutrition Examination Survey (NHANES) from 1976 to 2008. This allowed them to estimate trends in millions of American children. As expected, the overall blood pressure did not change much over time, but pulse pressure increased substantially and in parallel with the drastic increase in obesity rates.

Now that a trend has been identified, the next step is to figure out what specifically causes the pulse pressure increase in obese individuals. This in turn may explain the link between obesity and aortic function.

Zachariah’s team is in the middle of a clinical study of adolescents at Boston

Children’s that uses a three-pronged approach: 1) a combination of special equipment to noninvasively measure arterial stiffness; 2) echocardiography; and 3) a blood draw to measure markers in the blood. If the study is able to identify these drivers of aortic function, its findings may help prevent adult cardiac disease through early intervention.

Learn more about the Preventive Cardiology Clinic