Add Health

Hypertension may be much more common than expected among young adults, researchers found.
In the NIH-funded National Longitudinal Study of Adolescent Health (Add Health), the prevalence of hypertension in 24- to 32-year-olds was 19% in 2008, according to Quynh Nguyen, MSPH, a doctoral student at the University of North Carolina’s Gillings School of Global Public Health in Chapel Hill, and colleagues.
That compares with a rate of 4% among young adults participating in the National Health and Nutrition Examination Survey (NHANES) for a similar time period, the researchers reported online in Epidemiology.
Self-reported rates of hypertension, however, were similar in the two studies: 11% in Add Health and 9% in NHANES.Add Health principal investigator Kathleen Mullan Harris, PhD, also of the University of North Carolina at Chapel Hill, said on a conference call with reporters that there was no clear explanation for the discrepancy between the two studies.
“We tend to think of young adults as rather healthy, but a prevalence of 19% with high blood pressure is alarming, especially since more than half did not know that they had high blood pressure,” Harris said. Although the issue warrants further study, she added, “we think that the prevalence probably lies somewhere in between these two estimates.”
Add Health was started in 1994-1995 by enrolling more than 20,000 U.S. adolescents in middle school and high school. The students have been followed up periodically since then, most recently with Wave IV in 2008, when researchers began collecting in-home blood pressure measurements.
For comparison, the researchers used participants of similar age from NHANES 2007-2008. The cross-survey comparison included 14,252 Add Health participants and 733 NHANES participants.
Both the rate of blood pressure of 140/90 mm Hg or greater (19% versus 4%) and mean blood pressure (125/79 mm Hg versus 114/67 mm Hg) were higher in Add Health than in NHANES, which remained consistent in all sociodemographic subgroups.
Survey weights and propensity for differential selection into Add Health did not account for the different rates of hypertension observed in the two studies. After adjustment for numerous participant characteristics, examination time, use of antihypertensives, and consumption of food, caffeine, and cigarettes before blood pressure measurement, there was still a significantly increased likelihood of hypertension in Add Health (OR 6.6, 95% CI 4.0 to 11.0).
The researchers then examined other potential methodologic concerns, including digit preference, validity, reliability, measurement context, and interview content.