The number of young adults in the United States with high blood pressure may be much higher than previously reported, according to a new study by researchers at the University of North Carolina at Chapel Hill.
Researchers analyzed data on more than 14,000 men and women between 24 and 32 years old in 2008 from the National Longitudinal Study of Adolescent Health, known as Add Health, funded by the National Institutes of Health. They found 19 percent had elevated blood pressure, also referred to as hypertension. Only about half of the participants with elevated blood pressure had ever been told by a health-care provider that they had the condition.
"The findings are significant because they indicate that many young adults are at risk of developing heart disease, but are unaware that they have hypertension," said Quynh Nguyen, a doctoral student at UNC's Gillings School of Global Public Health and the study's lead author. Hypertension is a strong risk factor for stroke and coronary heart disease, the leading cause of death for adults in the U.S.
The findings were published online Monday, May 23, 2011, in the journal Epidemiology.
Kathleen Mullan Harris, Ph.D., Add Health's principal investigator, interim director of the UNC Carolina Population Center and a co-author of the paper, said the findings were noteworthy because they were from the first nationally representative, field-based study of blood pressure to focus on young adults. Other studies have concentrated on older adult populations, in which hypertension is more common, or have included only a small number of young adults, making it difficult to draw conclusions about that age group.
Harris said that the high rate of hypertension among the Add Health study participants was surprising. Another widely cited and reputable study – the National Health and Nutrition Examination Survey, or NHANES – reported a much lower rate of hypertension (4 percent) for a similar age group around the same time period (2007-2008). Both studies use the same definition of hypertension: a blood pressure reading of 140/90 mmHg (millimeters of mercury) or more.
"Our respective findings may differ, but the message is clear," said Harris. "Young adults and the medical professionals they visit shouldn't assume they're not old enough to have high blood pressure. This is a condition that leads to chronic illness, premature death and costly medical treatment.
"Our results show that the processes that trigger these problems begin early in life, but they are preventable, so it's important to check for hypertension now and head it off at the pass, in order to avoid these health and societal costs later on," Harris said.
UNC researchers considered several possible explanations for the discrepancy between the Add Health and NHANES estimates, including differences in the characteristics of participants, where they were examined (at home vs. examination center) and the accuracy and reliability of the measured blood pressures. None of these factors, however, could account for the gap in the hypertension estimates between the two surveys.
Also notable was the Add Health finding that the number of young adults with elevated blood pressure was almost twice the number who reported being previously told by a health-care provider that they had hypertension (11 percent). Eric Whitsel, M.D., head of the study's biology core, said that the finding was in line with expectations that measuring blood pressure will identify hypertension in otherwise healthy young adults who were unaware they had the condition. That pattern was reversed in NHANES, where the number of people found to have hypertension at the exam (4 percent) was half the number who reported a history of hypertension (9 percent).
The Add Health study also found males were much more likely than females to have hypertension (27 percent vs. 11 percent); and young adults without a high school degree were more likely than their college-educated peers to have the condition (22 percent vs. 17 percent).
The paper is titled "Discordance in National Estimates of Hypertension Among Young Adults." UNC authors were Nguyen; Harris, also James E. Haar Distinguished Professor of Sociology in the College of Arts and Sciences; Whitsel, from the epidemiology and medicine departments in the schools of public health and medicine, respectively; Joyce Tabor and Pamela Entzel with the Carolina Population Center; Chirayath Suchindran, Ph.D., professor of biostatistics in the public health school; and Jon Hussey, Ph.D., research assistant professor, and Carolyn Tucker Halpern, Ph.D., professor of maternal and child health, both in the public health school. Yan Lau, a doctoral student in the department of economics at Princeton University, also contributed to the paper.
The National Longitudinal Study of Adolescent Health is funded by grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, one of the National Institutes of Health. It also receives co-funding from 23 other federal agencies and foundations.
To read the paper, go to http://journals.lww.com/epidem/toc/publishahead (subscription required).
National Longitudinal Study of Adolescent Health website: http://www.cpc.unc.edu/projects/addhealth
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