Systolic and diastolic blood pressure levels for American children and teenagers have risen substantially since 1988, at least in part due to the increasing prevalence of overweight and obesity, according to an article in the May 5th issue of the Journal of the American Medical Association.

The current study involved 5,582 children ages 8-17 years who were part of the 1988-1994 and 1999-2000 National Health and Nutrition Examination Surveys. In both surveys, the children were about 50 percent male, 16-17 percent black, and 9-12 percent Mexican-American. The mean age for both groups was just under 13 years.

In 1988-1994, the average systolic pressure was 104.6 mm Hg and average diastolic pressure was 58.4 mm Hg. In 1999-2000, average systolic pressure was 106 mm Hg and average diastolic pressure was 61.7 mm Hg.

In the first survey, 11.7 percent of children were overweight; by 1999-2000, 16.3 percent were overweight. Overweight children and teenagers have a body mass index that falls in the 95th percentile or higher on age- and gender-specific growth charts compiled by the Centers for Disease Control and Prevention.

The systolic and diastolic blood pressure increases between the two surveys were large and occurred for all age and racial/ethnic groups and both genders. The systolic pressure increased by 1.4 mm Hg and the diastolic by 3.3 mm Hg from 1988-1994 to 1999-2000. Even after adjusting for body mass index, systolic and diastolic blood pressures were 1 and 2.9 mm Hg higher in 1999-2000 than in 1988-1994, suggesting that other factors such as physical activity and specific dietary nutrients were also contributing to the trend.

For the younger children (ages 8-12), yearly systolic and diastolic blood pressure increases were greater for girls compared with boys. For adolescents ages 13-17, yearly blood pressure increases were greater for boys compared with girls.

"The increases found by the study in children's average blood pressures may seem small, but they can have serious consequences," said Dr. Jeffrey Cutler, a coauthor of the paper.

"Previously published data indicate that, for each 1- to 2- mm Hg rise in their systolic blood pressure, children face a 10 percent greater risk of developing hypertension as a young adult."

As a response to the trend toward higher blood pressure in children, the National Institutes of Health will shortly release updated clinical guidelines on blood pressure evaluation and treatment in children and adolescents. The guidelines were recently presented in summary form at the annual meeting of the Pediatric Academic Societies. The updated data tables now include the 50th, 90th, 95th, and 99th percentiles of blood pressure by sex, age, and height.

Hypertension in youngsters is based on the range of blood pressures in healthy children. The new guidelines continue to define normal blood pressure as systolic and diastolic blood pressures that fall below than the 90th percentile for that sex, age, and height. To be consistent with the latest US blood pressure guidelines for adults, the guidelines for children include a prehypertension category. Children with a systolic or diastolic pressure equal to or greater than the 90th percentile but less than the 95th percentile are considered prehypertensive. Hypertension continues to be defined as a systolic or diastolic pressure equal to or greater than the 95th percentile.

There are significant metabolic and cardiovascular implications associated with the trends toward greater weight and higher blood pressure. Overweight and hypertension are components of the insulin resistance syndrome, a combination of multiple risk factors for cardiovascular disease and type 2 diabetes. Therefore, the guidelines call for a comprehensive assessment of cardiovascular risk factors. The new guidelines, noting the association of high blood pressure and overweight with sleep apnea, also suggest that a history of sleeping patterns should be obtained in a child with hypertension.

Treatment for children with high blood pressure usually consists of lifestyle changes, including weight management, physical activity, and dietary changes. Drug therapy is used if needed. The revised guidelines incorporate recent research and present updated recommendations for lifestyle approaches such as dietary changes for children and adolescents who have prehypertension as well as hypertension. Revised drug recommendations include dosage recommendations for many of the newer drugs studied in recent clinical trials.

Data tables from the new clinical practice guidelines on hypertension in children and adolescents are available at http://www.nhlbi.nih.gov/guidelines/hypertension/child_tbl.htm