The Q&A: Joshua Samuels

With each issue, Trib+Health brings you an interview with experts on issues related to health care. Here is this week’s subject:

Dr. Joshua Samuels is a pediatric nephrologist with the McGovern Medical School at UTHealth and the Children’s Memorial Hermann Hospital. He recently led a study that looked at the prevalence of high blood pressure among adolescents. The results of the study can be found here. 

Editor’s note: This interview has been edited for length and clarity.

Trib+Health: Your study found that high blood pressure was especially pronounced among obese Hispanic adolescents, compared to white, African-American or Asian adolescents. Do you have theories for why this was the case? 

Joshua Samuels: The study looked at all major races and ethnicities that are in Houston public and private schools, and 27 different schools participated. We measured blood pressure in fit kids, overweight kids and obese kids, and for the purposes of the study, patients self-identified their ethnicity as white, African-American, Hispanic or Asian.

A lot of other people have found the same thing we did, which is kids who were more obese had a higher risk of having high blood pressure. Among thin kids, high blood pressure was uncommon, and with each of the ethnic groups we looked at, we saw an increase in the rates of high blood pressure as their BMI percentile — their obesity, their weight — went up. We’ve known obesity is a major risk factor for high blood pressure in both kids and adults.

What this study shows is the relationship between weight and high blood pressure is not the same for each ethnic group we looked at. All of them had an increase in the rate of high blood pressure with increasing size, but it was much more pronounced in whites and Hispanics than it was in African-Americans and Asians.

There was a huge increase in high blood pressure with increasing obesity among white and Hispanic students. It wasn’t as big a deal for overweight white students because there weren’t that many of them, but 25 percent of Hispanic students were either overweight or obese, making them the largest group of obese students. 

Trib+Health: What were the most surprising findings in the study?    

Samuels: Compared to a thin Hispanic, an obese Hispanic had a six-fold increase in having high blood pressure — that’s not something we suspected we were going to find.

We saw an almost identical rise in obesity among African-Americans, but interestingly they didn’t have this exaggerated risk of high blood pressure. Among thin students, African-Americans had the highest rate of blood pressure, but among obese students, Hispanics overtook them by leaps and bounds.

Hispanics had an exaggerated response to obesity. Although there was somewhat of a linear relationship for African-Americans and Asians, there was a hyperbolic rise in the risk of high blood pressure among the Hispanic population. That steep rise was somewhat of a shock to us.

Trib+Health: What are some next steps moving forward?  

Samuels: Something we are doing that we didn’t initially do in the study is looking at weight circumference, because folks are starting to ask if body mass index — which is a simple height-to-weight ratio — is the most appropriate marker for obesity, or if should we look at height-to-weight circumference ratios.

We are also continuing to look at the best way to measure blood pressure. All of the normal blood pressure values that come out of the national studies on children use mercury on blood pressure readings. But those are being phased out more and more, and we are seeing a lot of automated blood pressure machines that measure blood pressure differently. We just don’t know how comparable those values are.

Some of our other research we are looking at involves questions like: What actual number do you write down for blood pressure, and how do you measure it? Do you use the mercury cuff, or are these other methods just as comparable? What is it about obese Hispanic students that place them at much higher risk for having high blood pressure — is it a cultural thing in their diet, or is it genetic? We really are just scratching the surface. We don’t know within any ethnicity what the specific factors are that leading to this increase in high blood pressure we’re seeing. That’s something I’d like to look at moving forward.

Trib+Health: Is there anything you’d like to add to today’s conversation? 

Samuels: It’s important to note that every child over three is supposed to have their blood pressure checked during routine doctor visits. As we were out there measuring blood pressure in kids, most of them said their blood pressure had been measured before, but a whole bunch said they had never had it measured. 

One of the messages here is high blood pressure, like in adults, is asymptomatic. You won’t know about the blood pressure problem unless you actually get it measured. This is common — 3 percent of kids in the community have sustained high blood pressure. You won’t know if you don’t measure.