WASHINGTON – Race and weight seem to work in concert to drive up blood pressure in Hispanic and white children, a study has shown.
"The interaction between race, obesity, and hypertension within any group is simple," Dr. Joshua Samuels said at the annual meeting of the Pediatric Academic Societies. "As kids become fatter, their rates of hypertension rise. But among Caucasian and Hispanic children, there’s a much more pronounced rise at a lower body mass index, with hypertension starting when the BMI reaches the 60th percentile."
Dr. Joshua Samuels
Dr. Samuels of the University of Texas Medical School at Houston* presented 12 years of data from his ongoing study of hypertension in public school students. So far, he and his colleagues have performed serial blood pressure screening on more than 20,000 children. Each child had blood pressure measurements on four separate occasions, with height and weight recorded each time.
After three measurements, each child was categorized as normotensive (three normal readings), prehypertensive (one hypertensive reading), or sustained hypertensive (three hypertensive readings).
The study population consisted of 20,729 racially and ethnically diverse students aged 10-18 years, with a mean age of 14.
A majority (64%) were normal weight, 18% were overweight, and 18% were obese.
"Obesity was prominent. All of these children were shifted toward the heavier range, and less than 2/3 was at a normal, healthy weight," Dr. Samuels said.
Hispanic and black youths were disproportionately overweight and obese, he said. Hispanic youths made up 34% of the study population but 44% of the obese group. Black youths made up 25% of the population but 30% of the obese group. Conversely, 34% of the population was white, but 22% of the obese group was white. Asian youths made up 7% of the population but 4% of the obese group.
Obesity was strongly associated with hypertension, with hypertension present in 1.6% of normal-weight youths, 2.6% of overweight youths, and 6.6% of obese youths.
While race alone was not significantly associated with hypertension, the interaction of race, weight, and hypertension was.
Among normal-weight youths when categorized by racial groups, hypertension clustered at 1.2%-2% for all groups. Among the overweight youths, hypertension was diagnosed in 1.8% of Asians, 2.4% of whites, 2.6% of Hispanics, and 2.9% of blacks.
Among obese children, however, more Hispanics (8%) and whites (7.5%) were hypertensive, compared with 4.5% of both Asians and blacks.
Furthermore, Dr. Samuels said, in whites and Hispanics, hypertension began at a much lower BMI. At the 50th percentile, hypertension clustered around 1.5%-2% for all racial groups. The groups began to separate around the 60th percentile, with blacks and whites having about a 1% higher rate of hypertension than Hispanics and Asians. By the 70th percentile, hypertension in Hispanics, blacks, and whites all clustered around 3%, with Asians below 2%. By the 90th percentile, hypertension in Asians was still less than 3%. It was around 3% in blacks, but was about 4% in Hispanics and whites.
The study wasn’t designed to investigate the reasons behind these differences, although Dr. Samuels said some of his colleagues are launching such a study. "My feeling is that there is some genetic component to it."
Whatever the reason, he said, the growing obesity problem among children portends ill for the next generation of adults.
"What we see now is a group of children who are obese, but what’s coming down the pike, if we’re not careful, is a huge undercurrent of adults with diabetes, stroke, blindness, cancer, kidney failure, and cardiovascular disease," he said.
Dr. Samuels said he had no relevant financial disclosures.
*This story was updated 5/6/13.