Blood Pressure Screening of School Children in a Multiracial School District: The Healthy Kids Project

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1 nature publishing group BRIEF COMMUNICATIONS Blood Pressure Screening of School Children in a Multiracial School District: The Healthy Kids Project William E. Moore 1,2, June E. Eichner 1,2, Eve M. Cohn 2, David M. Thompson 2, Cee E. Kobza 3 and Kathryn E. Abbott 3 Background There are few studies of the prevalence of elevated blood pressure (BP) that include American Indian school children. Therefore, the intent of this study was to examine the relationships between BP and risk factors in a multiracial, predominantly American Indian, school district. Methods A total of 1,829 American Indian, white, Hispanic, and African American students, 5 17 years old, were included in this study. The mean of two BP measurements, taken at the initial screening with an electronic BP monitor, were categorized as normal, prehypertensive, or hypertensive using the 2004 Fourth Report BP screening recommendations. Prevalence of prehypertensive and hypertensive BP measurements by race, gender, age, and body mass index (BMI) were determined, and their associations analyzed with logistic regression. Results The prevalence of prehypertensive measurements was 16.7% and prevalence of hypertensive measurements was 13.8% at first screen. Obesity was a risk factor for elevated BP for females and males (adjusted odds ratio (OR) = 4.01 and 4.33, respectively). Older age was also significantly associated with prehypertensive and hypertensive BP measurements, especially among males (adjusted OR = 6.91). Among females, American Indian race was protective against elevated BP (adjusted OR = 0.61). Conclusions Obesity was consistently associated with an increased risk for elevated BP. American Indian race was associated with decreased risk of elevated BP measurements in females. The high prevalence of obesity-related hypertensive measurements in this population that includes American Indian children was similar to levels found in other multiracial populations of school children when using BP measurements from a single assessment. Am J Hypertens 2009; 22: American Journal of Hypertension, Ltd. Screening for hypertension in children and adolescents has been recommended since the 1977 Report of the Task Force on Blood Pressure Control in Children. 1 Screening children for elevated blood pressure (BP) is important in order to implement preventive diet and exercise programs or pharmacologic treatment and to identify those at increased risk of cardiovascular disease as adults. 2 4 Some studies have reported differences in the unadjusted prevalence of elevated BP measurements among African American, white, and Hispanic children, but they were not statistically significant after adjusting for body mass index (BMI). 5,6 Very few studies of pediatric populations with 1 University of Oklahoma Prevention Research Center, College of Public Health, Oklahoma City, Oklahoma, USA; 2 Department of Biostatistics and Epidemiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA; 3 Anadarko Public Schools, Anadarko, Oklahoma, USA. Correspondence: William E. Moore (william-moore@ouhsc.edu) Received 15 May 2008; first decision 6 November 2008; accepted 24 December 2008; advance online publication 12 February doi: /ajh American Journal of Hypertension, Ltd. multiracial BP assessments have included American Indian children. 7 Therefore, the intent of this study was to assess and analyze BP and some associated risk factors among students in a predominantly American Indian school district. Methods Study participants: The Healthy Kids Project The Healthy Kids Project is an ongoing collaboration between the Anadarko, OK, public school district and the University of Oklahoma Prevention Research Center (Oklahoma City, OK). The Anadarko school district has approximately 2,000 students and six schools: three elementary schools, a middle school, a high school, and an alternative high school. In 2001, 77% of the Anadarko students were eligible for free or reduced price school lunches. 8 Beginning in 2001, children in the Anadarko Public Schools were asked to participate in screening for height, weight, and BP. 9 In , the school district included height, weight, and BP screening for all students within their school health assessment. Students were screened unless AMERICAN JOURNAL OF HYPERTENSION VOLUME 22 NUMBER APRIL

2 brief communications Blood Pressure Screening of Multiracial School Children parents opted out of health services provided by the school district. Investigators for the Healthy Kids Project received Institutional Review Board approval to analyze de-identified data collected during the student screening program for Screening was performed on 1,895 (95.7%) of the available Anadarko students. This study is limited to the 1,829 screened students under the age of 18 years because participants 18 years and older (n = 66) fall under adult guidelines. Measurements Students removed their shoes before height measurements were made. Height was measured to the nearest 0.1 cm using a Seca Road Rod stadiometer (Seca, Hanover, MD). Shoes and heavy outer clothing, such as coats and jackets, were removed before weight was measured. A digital Tanita BWB- 800A scale (Tanita, Arlington Heights, IL) recorded weight to the nearest 0.2 kg. Epi Info (Centers for Disease Control and Prevention software) was used to generate BMI and BMI percentiles for age and gender. BMI percentiles were classified in the following age and gender specific categories: underweight <5th percentile, normal 5th percentile and <85th percentile, overweight 85th percentile and <95th percentile, and obese 95th percentile. 10 Omron HEM-907 IntelliSense digital electronic BP monitors (Omron Healthcare, Schaumburg, IL) were used to measure BP. 11 Participants were fitted with a small, medium, or large BP cuff depending on arm size in accordance with cuff guidelines and index marks on the cuffs. Students sat quietly with their right arm resting at heart level on a table for 3 5 min before their BP was measured. Two BP measurements were taken with 1 min in between, and the average diastolic and systolic BP measurements were recorded. All BP measurements were supervised or performed by two Anadarko school nurses (C.E.K., K.E.A.). Trained staff of the University of Oklahoma Prevention Research Center provided assistance in the measurement of BP, height, and weight. Based on the 1996 Update on the 1987 Task Force Report on High Blood Pressure in Children and Adolescents, students with elevated BP were remeasured on two more occasions if their BP remained elevated. 12 Those with elevated measurements on three occasions were finally assessed by the school nurses using mercury sphygmomanometers with appropriate follow-up when needed. Elevated BP measurements found at a single screening are not useful for diagnosing hypertension but are useful for examining population trends. Initial screening measurements were therefore designated as normal, prehypertensive, or hypertensive to describe BP levels without the inference of a diagnosis. For this analysis, BP measurements were categorized using the age, gender, and height specific recommendations of the 2004 Fourth Report by the National High Blood Pressure Education Program Working Group on Hypertension Control in Children and Adolescents. 13 The 2004 Fourth Report categories are as follows: normal BP measurements <the 90th percentile, prehypertensive BP measurements the 90th percentile and <the 95th percentile, hypertensive BP measurements the 95th percentile. was determined by using student records for those in grades kindergarten to 6 and by student self-report for grades 6 through 12. Statistical analysis NCSS 2007 software (NCSS; Kaysville, UT) was used for the data analysis. Data collected on 15 underweight students were combined with data from the normal weight students to Table 1 Mean blood pressure and body mass index by age and gender Mean BMI (s.d.) Mean SBP/DBP (s.d./s.d.) Age year N (female/male) Female Male Female Male (64/59) 17.3 (2.3) 16.6 (2.4) 101.0/61.8 (6.7/7.1) 99.2/58.7 (10.4/8.2) (72/74) 18.0 (3.6) 18.2 (3.8) 100.5/60.2 (8.9/7.0) 102.7/59.4 (9.4/7.3) (81/72) 19.6 (4.5) 18.4 (3.6) 101.9/61.3 (8.4/9.3) 105.2/61.8 (6.6/6.8) (79/86) 19.0 (3.9) 19.4 (4.5) 102.4/61.6 (9.8/9.8) 104.6/61.0 (7.7/8.4) (62/83) 19.9 (3.9) 20.2 (4.7) 103.1/62.1 (9.1/10.0) 105.4/61.5 (10.3/8.2) (92/99) 21.7 (4.9) 21.3 (5.5) 105.7/61.9 (9.6/8.7) 106.2/61.4 (10.3/8.3) (73/62) 22.4 (5.2) 22.0 (5.8) 107.3/62.4 (10.5/9.7) 107.6/61.9 (10.2/8.4) (67/75) 23.7 (4.8) 23.3 (6.3) 112.5/65.1 (10.1/9.0) 110.7/61.7 (11.1/8.0) (62/70) 26.0 (6.6) 24.6 (6.8) 115.5/66.6 (9.6/8.3) 116.1/62.8 (10.2/8.6) (63/63) 25.7 (6.2) 25.9 (7.4) 115.0/66.0 (10.8/9.2) 124.6/65.6 (13.9/9.0) (83/67) 25.8 (6.6) 24.3 (5.5) 115.4/65.6 (9.9/7.7) 123.4/64.6 (12.1/8.4) (58/54) 25.8 (6.3) 25.4 (5.4) 117.0/67.9 (10.1/9.4) 128.7/68.4 (14.0/10.5) (50/59) 25.4 (7.1) 27.3 (7.0) 116.0/67.2 (10.6/7.1) 131.8/67.3 (11.6/8.7) Total 1,829 (906/923) 22.2 (6.0) 21.9 (6.2) 108.3/63.6 (11.4/9.0) 111.8/62.5 (14.5/8.7) BMI, body mass index; DBP, diastolic blood pressure; SBP, systolic blood pressure. 352 APRIL 2009 VOLUME 22 NUMBER 4 AMERICAN JOURNAL OF HYPERTENSION

3 Blood Pressure Screening of Multiracial School Children brief communications Table 2 Crude odds ratios for elevated blood pressure risk Gender Female BMI Male Variables Prehypertensive vs. normotensive Hypertensive vs. normotensive Prehypertensive or hypertensive vs. normotensive Crude odds ratios (95% CI) Crude odds ratios (95% CI) Crude odds ratios (95% CI) Overweight 1.29 (0.77, 2.14) 1.66 (0.96, 2.87) 1.44 (0.97, 2.14) Obese 2.40 (1.57, 3.67) 3.54 (2.25, 5.57) 2.88 (2.05, 4.03) BMI years 2.52 (1.72, 3.69) 1.75 (1.18, 2.59) 2.11 (1.57, 2.84) American Indian 0.66 (0.43, 1.01) 0.70 (0.45, 1.07) 0.68 (0.49, 0.94) African American 1.27 (0.58, 2.81) 0.83 (0.32, 2.12) 1.06 (0.55, 2.05) Hispanic 1.05 (0.46, 2.35) 0.50 (0.17, 1.50) 0.78 (0.39, 1.57) Overweight 1.36 (0.85, 2.19) 2.48 (1.46, 4.21) 1.74 (1.19, 2.55) Obese 2.28 (1.56, 3.34) 4.45 (2.87, 6.90) 3.02 (2.20, 4.14) years 6.60 (4.54, 9.58) 6.72 (4.44, 10.18) 6.65 (4.91, 9.02) American Indian 0.82 (0.57, 1.19) 1.04 (0.67, 1.61) 0.90 (0.66, 1.23) African American 1.01 (0.48, 2.13) 1.50 (0.68, 3.32) 1.20 (0.65, 2.19) Hispanic 0.52 (0.23, 1.16) 1.37 (0.67, 2.79) 0.84 (0.47, 1.49) BMI, body mass index; CI, confidence interval. create three BMI categories: underweight or normal weight, overweight, and obese. Associations of elevated BP measurements with race, gender, age, and BMI were explored with logistic regression models by dichotomizing the Fourth Report s three BP categories into outcome variables in three ways: prehypertensive BP compared to normal BP, hypertensive BP compared to normal BP, and prehypertensive or hypertensive BP compared to normal BP. In all analyses, age was categorized into two groups, those 5 11 years old and those years old. The variables BMI, race, age, and gender were initially included in a logistic model that included interaction terms. Because of the interaction detected between gender and age group, all subsequent logistic regression analyses were repeated for each gender. Gender specific logistic regression, performed separately on the three dichotomized outcomes for BP, provided adjusted odds ratios (ORs) and their 95% confidence intervals (95% CI) for the contribution of age, gender, race, and BMI to prehypertensive, hypertensive, and combined prehypertensive/ hypertensive BP. Results Among the 1,829 (92.4%) screened students included in the study, the proportions of each mutually exclusive racial category were as follows: 60.5% American Indian (571 female, 536 male), 27.7% white (241 female, 265 male), 6.3% Hispanic (47 female, 68 male) and 5.5% African American (47 female, 54 male). The female/male breakdown was roughly equal with 49.5% females and 50.5% males. Prevalence of elevated BP measurements Table 1 shows mean BMI and systolic and diastolic BP by age group and gender. Normal BP was recorded for 72.5% of the female students and 66.6% of the male students (69.5% combined). Prehypertensive BP was present in 14.6% of the female students and 18.9% of the male students (16.7% combined), while hypertensive BP was present in 13.0% of the female students and 14.5% of the male students (13.8% combined). Using 4th Report criteria and the method of Sorof et al. for calculating follow-up BP assessment prevalence rates, 13.8% of the students had hypertensive BP at first measurement, 4.5% at second measurement, and 2.3% at third measurement. 5 AMERICAN JOURNAL OF HYPERTENSION VOLUME 22 NUMBER 4 APRIL

4 brief communications Blood Pressure Screening of Multiracial School Children Table 3 Adjusted logistic regression odds ratios for elevated blood pressure risk a Gender Female Male Variables BMI Prehypertensive vs. normotensive Hypertensive vs. normotensive Prehypertensive and hypertensive vs. normotensive Adjusted odds ratios (95% CI) a Adjusted odds ratios (95% CI) Adjusted odds ratios (95% CI) a Overweight 1.29 (0.77, 2.18) 1.69 (0.97, 2.94) 1.47 (0.98, 2.20) Obese 2.74 (1.76, 4.29) 4.01 (2.51, 6.41) 3.19 (2.25, 4.54) years 2.56 (1.73, 3.80) 1.83 (1.21, 2.77) 2.14 (1.58, 2.91) American Indian 0.60 (0.39, 0.95) 0.61 (0.38, 0.96) 0.61 (0.43, 0.87) African American 1.21 (0.53, 2.78) 0.76 (0.28, 2.02) 0.98 (0.49, 1.97) Hispanic 0.89 (0.39, 2.06) 0.35 (0.11, 1.09) 0.64 (0.31, 1.31) Number (+, ) b 132, , , 656 BMI Overweight 1.44 (0.86, 2.41) 2.48 (1.41, 4.36) 1.78 (1.17, 2.71) Obese 2.64 (1.72, 4.05) 4.33 (2.69, 6.96) 3.34 (2.33, 4.79) years 6.84 (4.66, 10.04) 6.72 (4.35, 10.37) 6.91 (5.03, 9.50) American Indian 0.88 (0.58, 1.33) 1.12 (0.68, 1.83) 0.96 (0.67, 1.38) African American 1.12 (0.49, 2.57) 1.39 (0.56, 3.44) 1.24 (0.62, 2.48) Hispanic 0.57 (0.24, 1.34) 1.39 (0.62, 3.08) 0.87 (0.46, 1.66) Number (+, ) b 174, , , 615 BMI, body mass index; BP, blood pressure; CI, confidence interval. a Each variable is adjusted for every other variable in its respective column. b The number in the respective column with prehypertensive, hypertensive, or either BP measurement (+) and those with normal BP ( ). There was a significant difference between females and males in BP status (χ 2 2df = 7.95, P = 0.02) with male students having higher rates of prehypertensive and hypertensive BP measurements. However, this difference was only significant among adolescents years old (χ 2 2df = 32.27, P < 0.01). There was no gender difference among children 5 11 years old (χ 2 2df = 5.54, P = 0.06). Association of elevated BP measurements with age, gender, BMI, and race Table 2 shows the unadjusted ORs for the relationship between BP status and BMI category, age group, and race for both female and male students. Table 3 shows separate logistic regression models for females and males and gives adjusted ORs and 95% confidence intervals (CIs) for BMI category, age group, and race for each of the three comparisons. Females years old had increased risk for hypertension (OR = 1.83, 95% CI: 1.21, 2.77) compared to females 5 11 years old. However, for year-old males, the risk is much greater (OR = 6.72, 95% CI: 4.35, 10.37). Obesity was also a significant risk factor, of similar strength in both genders: for prehypertension ((female OR = 2.74, 95% CI: 1.76, 4.29) (male OR = 2.64, 95% CI: 1.72, 4.05)) and for hypertension ((female OR = 4.01, 95% CI: 2.51, 6.41) (male OR = 4.33, 95% CI: 2.69, 6.96)). Among females, being of American Indian heritage was uniformly protective against prehypertensive BP (OR = 0.60, 95% CI: 0.39, 0.95) and hypertensive BP (OR = 0.61, 95% CI: 0.38, 0.96). Discussion The prevalence of BP measurements from in the hypertension category on initial screening reported in multiracial US populations of children and adolescents varies from %. 5,6,14 16 It is important to note that this broad range was shown for United States National Health Survey data from that was analyzed using the 4th report criteria for 354 APRIL 2009 VOLUME 22 NUMBER 4 AMERICAN JOURNAL OF HYPERTENSION

5 Blood Pressure Screening of Multiracial School Children brief communications BP classification. 13,14 The current study found a hypertensive measurement prevalence of 13.8% in a multiracial, low income, rural population of school children. The students in this analysis also had a high prevalence of obesity and overweight with 29.0% obese, 19.2% overweight, 50.9% normal weight, and 0.8% underweight. The prevalence of obesity and overweight was especially pronounced among American Indians with 33.2% obese, 19.6% overweight, 46.3% normal weight, and 0.8% underweight. Among white students, 20.0% were obese, 17.6% were overweight, 61.3% were normal weight, and 1.2% were underweight. Consistent with other investigations, obesity was a risk factor for elevated BP in both females and males. Males in the Anadarko schools did not differ in risk for elevated BP measurements by race. However, American Indian females had significantly reduced risk for elevated BP when also adjusting for BMI and age group (OR = 0.61, 95% CI: 0.43, 0.87). Other prevalence studies of hypertensive BP measurements that compared African American, white, and Hispanic school children found no difference in risk of elevated BP measurements by race. 5,6 The present study was able to compare BP in a large sample of American Indian school children to peers from other races within the same community. Evidence exists that supports the possibility that this protective effect is not a chance finding. In the Strong Heart Study, a study of cardiovascular risk factors in adult American Indian populations, obesity had a smaller impact on BP than in other populations. 17 With respect to gender, American Indian females have a lower risk of hypertensive BP despite the presence of higher obesity rates when compared to American Indian males. 18 This relationship may be similar in children and adolescents and possibly unique to American Indian females. Gender differences in the risk of elevated BP in children and adolescents are reported in a number of studies. 5,6 Androgue and Sinaiko, in their reassessment of data collected in the 1980s using recommendations from the 1996 Updated Task Force Report, found median systolic BP higher in males and diastolic BP higher in females. 19 The present study found differences in risk for elevated BP measurements by gender and age, with males showing a dramatic increase in risk for elevated BP among those 12 years old and older. This large male/female difference may be related to the screening process. Female staff and nurses performed 99% of the BP measurements. Perhaps the male participant/female nurse interaction contributed to the higher levels of elevated BP in the adolescent males. It is also possible that adolescent males were more agitated by the entire screening process than were adolescent females. The childhood obesity epidemic may necessitate a new screening focus on cardiovascular risk factors, such as BP, lipids, central obesity, and fasting glucose that have historically been of less concern among the young. The current investigation has demonstrated that two long standing adult risk factors for hypertensive BP, age and weight status, are also substantial risk factors among a multiracial cohort of children and adolescents. Limitations A limitation of this study is the fact that logistical considerations necessitated the use of electronic oscillometric BP monitors. There is some evidence that the automatic pressurization of the BP cuff when using electronic BP monitors may be a stressor that artificially increases children s BP readings. 20 However, this limitation should not affect the inferential comparisons of the associations of gender, age, and obesity with elevated BP. Lastly, there have been many divergent protocols for the assessment of pediatric blood pressure over time. These differences always make comparisons between studies difficult and problematic. Instrumentation may be less important than other measurement protocol differences. Lastly, the small number of Hispanic and African American students limits inferential conclusions for these two groups. Acknowledgments: This publication was supported by Cooperative Agreement Number U48DP from the Centers for Disease Control and Prevention, Prevention Research Center Program. The findings and conclusions in this publication are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. Disclosure: The authors declared no conflict of interest. 1. Blumenthal S, Epps RP, Heavenrich R, Lauer RM, Lieberman E, Mirkin B, Mitchell SC, Boyar Naito V, O Hare D, McFate Smith W, Tarazi RC, Upson D. Report of the task force on blood pressure control in children. Pediatrics 1977; 59 (5 2 suppl): I II, Chen X, Wang Y. Tracking of blood pressure from childhood to adulthood: a systematic review and meta-regression analysis. Circulation 2008; 117: Gidding SS, Barton BA, Dorgan JA, Kimm SY, Kwiterovich PO, Lasser NL, Robson AM, Stevens VJ, Van Horn L, Simons-Morton DG. Higher self-reported physical activity is associated with lower systolic blood pressure: the Dietary Intervention Study in Childhood (DISC). Pediatrics 2006; 118: Lauer RM, Clarke WR. 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