High Blood Pressure in School Children: Prevalence and Risk Factors

Ximena Urrutia-Rojas; Christie U. Egbuchunam; Sejong Bae; John Menchaca; Manuel Bayona; Patrick A. Rivers; Karan P. Singh

Disclosures

BMC Pediatr 

In This Article

Methods

Data for this study was obtained from a previous study involving children from seventeen schools in Fort Worth, Texas. The schools were selected following a non-probabilistic sampling procedure developed by the investigators and the Independent School District (ISD) Director of Health Services in order to reflect the ethnic and geographical profile of the school district's student population. Of the total number of fifth graders (n = 1,500), 1,076 of those 8-13 years of age agreed to participate. Since there were missing values for 10 of these children, the final data set used in the analysis included 1,066 children.

Parents/guardians were provided with a description of the project, informed consent forms, and a family history/lifestyle questionnaire (written in both English and Spanish). If willing to allow their child to participate, parents/guardians were then asked to sign the informed consent form and complete the family history/lifestyle questionnaire. Children agreeing to participate signed the assent form. In addition, trained research assistants explained the study procedures and measurements to the participants. Information included in the dataset were age, date of birth, gender, ethnicity, height, weight, body mass index (BMI), systolic and diastolic blood pressure (SBP and DBP, respectively), and presence or absence of AN. Data were obtained from physical examination and completion of the questionnaire.

The classification of BP percentiles for this study was determined using normative tables generated from the National Health and Nutrition Examination Survey (NHANES) data submitted by the 1996 National High Blood Pressure Education Program Working Group on Hypertension Education in Children and Adolescents, which take into account the age, gender and height of each child.[2] The 95th percentile was used to determine HBP for each child's age, gender, and height.

Children were weighed wearing light clothes and no shoes. Weight was recorded in pounds using a Tanita Model TBF-300 digital electronic scale. Height was recorded in inches to the nearest 1/16th of an inch using a portable stadiometer. All measurements were recorded between 8:30 a.m. and 11:00 a.m. Weight and height were converted to metric measurements in order to determine the BMI, which is represented as weight (kg) divided by the square of height (m2). Children with a BMI value ≥ 85th percentile for age and sex were classified as being overweight.[38] Overweight and obese categories were combined in this study and are described as obese in this paper.

AN, as assessed by the research team pediatrician, was recorded as level 0-4, with 0 representing the absence of the condition.[36,37] Due to the small number of cases among the children, levels 1-4 were combined into aggregate categories of either "AN present" or "AN absent".

BP was measured after the child rested for at least 5 minutes in a sitting position. A registered nurse from the local Cook Children's Hospital performed BP measurements with an automated Dinamap 8100 XL monitor.[39,40,41] If the readings indicated that the BP was elevated or in the range for hypertension (90th or 95th percentile, respectively, based on normative BP tables that take into account height, age and gender measured on at least three separate occasions), a second and third reading was taken after the child had rested for an additional 20 minutes. Since in this study BP was assessed on a single set of 3 measurements for all participants, to minimize misclassification average SBP and DBP was recorded.[2] According to the criterion set forth in the 1996 task force report on HBP in children and adolescents,[2] in this study, hypertension in children was defined as average SBP or DBP ≥ 95th percentile for age, sex, and height measured on at least three separate occasions. Elevated or high normal BP was defined as average SBP or DBP ≥ 90th percentile, but less than the 95th percentile.[2] Since BP was assessed using a single set of measurements, the 95th percentile was used as the cut point to determine high BP in this study.

Data analysis was performed using the SPSS statistical package (SPSS for Windows Version 11.5, 2002). The prevalence of SBP and DBP ≥ 95th percentile in the study population, as well as the prevalence of isolated SBP and DBP ≥ 95th percentile, were computed. Children with BP ≥ 95th percentile were compared to children with BP < 95th percentile regarding the association of potential covariables. The odds ratio was used as a measure of association. The crude associations were obtained for BP ≥ 95th percentile with potential factors such as obesity. Multiple logistic regression analysis was used to assess the association of each covariable and BP ≥ 95th percentile, adjusting for all potentially confounding variables simultaneously. To assess precision, the 95 % C.I. was calculated for crude and adjusted odds ratios.[42,44]

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