How big of a risk is high blood pressure for young people? The answer could depend on which study you trust. A recent study found that nearly 20 percent of young adults have elevated blood pressure. That number dwarfs the 4 percent figure the Centers for Disease Control and Prevention came up with in 2008 — and researchers aren’t sure why their findings vary so drastically.
In 2008, scientists from the CDC released data on the rates of high blood pressure, or hypertension, across the population based on information collected through its National Health and Nutrition Examination Survey. The hypertension portion of the survey included data from 9,762 participants.
Researchers reported that for the 24-to-32 age group, about 4 percent had blood pressure readings of 140/90 or higher, which indicates hypertension. This number has been widely cited and guides policy decisions within CDC and beyond.
Working with different data taken from the 2008 National Longitudinal Study of Adolescent Health, funded by the National Institutes of Health, researchers from the University of North Carolina at Chapel Hill found different results.
Quynh Nguyen, a graduate student studying public health, led the study and found that even though the studies used the same definition of hypertension, about 19 percent of the approximately 15,000 participants, ages 24 to 32, met that criteria. These findings were published this week in the journal Epidemiology.
Their findings also differed with regard to whether study participants with hypertension had been made aware of that fact. In the NHANES study, researchers found that while only 4 percent of their participants had hypertension, 9 percent of them reported a history of hypertension, suggesting that more people report having it than actually do.
That trend was reversed in the Add Health study. Nguyen and colleagues found that of their 19 percent with hypertension, 11 percent reported being told by their physicians that they had high blood pressure.
Why such striking differences between the two studies? According to Nguyen and colleagues, there might have been stark differences in the populations studied. The Add Health study was more likely to include non-Hispanic white, U.S.-born, highly educated and well-insured people than the NHANES study, for instance.
Vicki Burt, a health statistics researcher at CDC and chief of the planning branch of NHANES, thinks the discrepancy could potentially be chalked up to the Add Health team’s relative inexperience in taking blood pressure measurements.
“There are aspects of the methods that we do in NHANES that we know are very important because we’ve been doing this for so many years,” Burt said. “Some of the nitty-gritty makes a big difference.”
Details like the size of blood pressure cuffs, machine types and technician training can influence readings, and they could account for Add Health’s divergent results. The NHANES findings have been consistent across several decades, Burt added, and jibe with other studies that have been done on hypertension prevalence among young people.
Whether differences in the populations measured could be a factor is a question for future research, as it’s not clear whether those differences could account for such an anomalous result, Burt said.
The upside of this controversy is that it will spur further research, which will lead to a better understanding of how hypertension affects young people, she said — whether it’s four or 20 percent of them.
hypertension,high blood pressure,CDC,National Longitudinal Study of Adolescent Health,NHANES,young adults
