Sep. 11, 2007 A Morehouse School of Medicine (MSM) researcher is the lead author of a new study that finds that after decades of decline, blood pressure (HBP) levels in children and adolescents are increasing.
"General obesity, called 'overweight' in childhood, increased over time in all racial and ethnic groups," said Rebecca Din-Dzietham, M.D., M.P.H., Ph.D., lead author of the study and associate professor of community health and preventive medicine at MSM in Atlanta, Ga. "The prevalence of childhood obesity drifted slightly and steadily higher after the 1963 survey and increased significantly during the 1976-1980 survey period with a sharp rise after that time."
Din-Dzietham said that each one centimeter increase in waist circumference raised the likelihood of high blood pressure by 10 percent and the likelihood of pre-high blood pressure by five percent.
The study is based on an analysis of national health surveys between 1963 and 2002 published in Circulation: Journal of the American Heart Association.
Researchers analyzed data from seven U.S. government surveys conducted in children and adolescents ages eight to 17 between 1963 and 2002. They examined trends in the age-adjusted prevalence of high blood pressure and pre-high blood pressure in boys and girls. They also looked at trends in various racial/ethnic groups and the impact of increasing obesity on those trends. Some of the government surveys included children younger than eight, but their data were removed from the analysis.
Normal blood pressure was defined as having both systolic pressure (the upper number representing the pressure when the heart contracts, or beats) and diastolic pressure (the lower number representing the pressure when the heart relaxes between beats) below the 90th percentile. Pre-HBP was defined as either a systolic or diastolic blood pressure above the 90th percentile but below the 95th percentile or having blood pressure levels above 120/80 mm Hg, but below 95th percentile. HBP was defined as either systolic or diastolic blood pressure at or above the 95th percentile.
The prevalence of HBP and pre-HBP in children and adolescents showed a downward trend between 1963 and the 1988-1994 survey. But the trend began to reverse through 2002. For example, the prevalence of high blood pressure in all children and adolescents decreased from 11.1 percent in the 1976-1980 (Black and white) and 4.7 percent in 1982-1984 survey (first national survey for Mexican-American youth) to 2.7 percent in the 1988-1994 survey (all children), but rose to 3.7 percent in the 1999-2002 survey (all children).
The change was even more pronounced among Mexican-American males. For them, the prevalence of high blood pressure dropped from 6.1 percent in 1982-1984 to 3.1 percent in 1988-94 before rising to 5.3 percent in 1999-2002, making of them the subgroup with the largest and significant rise, 2.2 percent, in high blood pressure prevalence.
Pre-high blood pressure is relevant because the long-running Bogalusa (La.) Heart Study found that children whose blood pressure was chronically at or above the 90th percentile showed signs of early organ damage as young adults, such as greater thickening of the heart wall or higher amounts of a protein called albumin in the urine.
Autopsies on adolescents and young adults who were in the Bogalusa study, but died by accident (so supposedly healthy) also found that those with elevated blood pressure were more likely to have atherosclerotic lesions in their aorta than those with normal blood pressure.
The researchers studied two kinds of overweight measures: body mass index (BMI), a measure of general overweight; and waist circumference, a measure of abdominal obesity. Although BMI and waist circumference were both associated with elevated blood pressure prevalence, the rise in abdominal obesity explained more of the rise in elevated blood pressure prevalence than did the rise in general obesity, Din-Dzietham said. For example, if the prevalence of obesity had not increased between 1988-1994 and 1999-2002, in 1999-2002 the prevalence of pre-HBP would have been lower by 64 percent when considering abdominal obesity and 27 percent lower when considering general obesity.
High blood pressure is a major public health problem in adults and a common risk factor for heart attack and stroke.
"This is a major public health problem," Din-Dzietham said. "Unless this upward trend in high blood pressure is reversed, we could be facing an explosion of new cardiovascular disease cases in young adults and adults. To reverse the upward trend at the beginning is good, and that's why we need to act now."
Co-authors are Yong Liu, M.S.; Marie-Vero Bielo, M.D.; and Falah Shamsa, Ph.D.
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