Study Confirms Impact of Environmental Factors on Hypertension

Additional data from the Bogalusa Heart Study presented today at the American Society of Hypertension's Twenty Fourth Annual Scientific Meeting (ASH 2009) suggest that the relationship between low birth weight and hypertension becomes stronger as individuals become older, particularly in white males as opposed to females or blacks.

In addition, a separate analysis revealed that variations in blood pressure (BP) measurements in children are related to the development of hypertension in adulthood, especially in blacks. Both studies reveal that BP responses to environmental factors as children grow into adults may play an important role in the development of hypertension.

The Bogalusa Heart Study is the longest and most detailed epidemiologic study of a biracial (black-white) population of children in the world. The study focuses on understanding the early natural history of coronary artery disease and essential hypertension. It is the only major program studying a total and geographically well-defined, biracial and semi-rural community.

"Both substudies presented today show that the environmental factors children face as they age affect their chances of developing hypertension in adulthood, regardless of other risk factors. To help address this, we recommend low dose medication for young individuals tracking above the 90th percentile, exercise and a nutritional diet for at risk children, especially when obese, along with comprehensive health education," said Gerald Berenson, M.D., professor of cardiology at the Tulane Center for Cardiovascular Health in New Orleans. "We have developed the public health model Health Ahead/Heart Start Program for elementary school children and it is hoped that such measures can be implemented to help to reduce children's risk."

Relationship Between Low Birth Weight and Hypertension
Low birth weight is associated with elevated blood pressure levels later in life; however, a recent debate has focused on how age may amplify the strength of that association. In this substudy involving 6,875 individuals (62 percent whites; 38 percent blacks, 40 percent males), subjects were examined 1-12 times for BP from childhood through to adulthood with 23,521 observations. Information on birth weight and gestational age was obtained from birth certificates.

Blacks showed a significantly higher systolic BP (SBP) in adolescence and adulthood and lower birth weight than whites. In a multivariate regression analysis, low birth rate was associated with higher SBP levels at all ages in the combined sample of blacks and whites, but this association did not differ significantly between races or sexes. Importantly, the strength of the birth weight SBP relationship was amplified with increasing age and stronger in males and whites respectively (although decreasing trends with age were noted for both sex and race groups).

Long-Term Effect of Blood Pressure Variability in Children
Increased BP variability is associated with severity of end-organ damage and higher rate of cardiovascular events. This substudy tested the hypothesis that children's BP variability is more strongly associated with hypertension in adulthood than normal levels.

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A cohort of 1,797 adults (1,091 whites and 706 blacks, 44 percent male; age 21-48 years) were examined 4-8 times for BP during childhood (mean age 13.1 years) with 9035 measurements of BP. Results showed that hypertension was more prevalent in blacks and they had significantly greater variability in SBP levels than whites. Hypertension in adulthood was significantly associated with measures of BP variability in childhood, except for SBP. Further, the childhood BP variability was a stronger predictor of adulthood hypertension than childhood BP levels.

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