Journal of Adolescent Health 55 (2014) 521e527
www.jahonline.org Original article
Long-Term Predictors of Blood Pressure Among Adolescents During an 18-Month School-Based Obesity Prevention Intervention Nayoung Kim, M.A. a, Dong-Chul Seo, Ph.D., FAAHB b, *, Mindy H. King, Ph.D. c, Alyssa M. Lederer, M.P.H. a, c, and Danielle Sovinski, M.P.H. c a
Department of Applied Health Science, Indiana University School of Public Health, Bloomington, Indiana College of Health Sciences, Ewha Womans University, Seoul, South Korea c Center on Education and Lifelong Learning, Indiana University, Bloomington, Indiana b
Article history: Received October 2, 2013; Accepted April 14, 2014 Keywords: Blood pressure; School health; Longitudinal cohort; Obesity intervention
A B S T R A C T
Purpose: To evaluate the effectiveness of the HEROES (Healthy, Energetic, Ready, Outstanding, Enthusiastic Schools) initiative, a multicomponent school-based obesity prevention intervention based on the Centers for Disease Control and Prevention’s coordinated school health approach, on the improvement of blood pressure (BP) and to determine long-term predictors of systolic and diastolic BP changes among high school students who were exposed to the intervention. Methods: Biometric and behavioral data from high school students were analyzed at baseline, 6, 12, and 18 months (N ¼ 847, three schools). The attrition rate at 18 months was 26.1%. Sequential generalized estimating equation models were fit to the data using SAS 9.3, taking into account clustering effects within the same school and correlations within repeated measures. Results: A significant downward trend was observed in systolic BP (p ¼ .0006) and diastolic BP (p < .0001) among the students who were exposed to the HEROES initiative. The prevalence of hypertension decreased from 17.1% at baseline to 12.8% at 6 months (p < .0001), 12.0% at 12 months (p < .0001), and 15.0% (p ¼ .0024) at 18 months. Baseline body mass index, increases in body mass index percentiles, and increases of television-viewing hours were associated with BP increases. Increases in frequencies of eating french fries or chips, skipping breakfast, and consuming supersize meals when eating fast food were predictive of systolic BP changes, not of diastolic BP changes. Conclusions: An 18-month multicomponent school-based obesity intervention program may be effectively used to decrease rates of high BP among adolescents. Ó 2014 Society for Adolescent Health and Medicine. All rights reserved.
High blood pressure (BP) in children and adolescents has become a nationwide concern over the past several years because of its escalating prevalence. Data from the National Health and Nutrition Examination Survey III with U.S. children Conflicts of Interest: There are no actual or potential conflicts of interest involved with this study. * Address correspondence to: Dong-Chul Seo, Ph.D., FAAHB, College of Health Sciences, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul 120-750, South Korea. E-mail address:
[email protected] (D.-C. Seo).
IMPLICATIONS AND CONTRIBUTION
The present study showed that a multicomponent school-based obesity intervention may be effectively used to decrease adolescents’ blood pressure. This study confirms the need for and efficacy of the desirable nonpharmacological treatments for adolescents to maintain healthy BP. It highlights the importance of maintaining healthy weight, a decrease in sedentary behavior, and healthy dietary habits among adolescents to maintain normal BP.
and adolescents showed that the mean of systolic BP and diastolic BP increased by 1.4 mm Hg and by 3.3 mm Hg, respectively, between 1988e1994 and 1999e2000 [1]. Another nationally representative study reported that, concurrent with the obesity epidemic, the incidence of prehypertension and hypertension in youth has been on rise since the late 1980s [2]. Elevated BP causes target organ damages such as left ventricular hypertrophy and is linked with immune and metabolic abnormalities in children and adolescents [3]. Furthermore, elevated BP in adolescence is predictive of hypertension in adulthood,
1054-139X/$ e see front matter Ó 2014 Society for Adolescent Health and Medicine. All rights reserved. http://dx.doi.org/10.1016/j.jadohealth.2014.04.011
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contributing to a great burden of worldwide premature morbidity and mortality [4]. It is therefore important to have a better understanding of factors related to high BP among adolescents. Adolescence is a critical transition period between childhood and adulthood, which brings rapid physical growth and behavioral alterations. During this formative stage, adolescence is characterized by physiological changes, such as excessive weight gain and decreasing insulin sensitivity, and behavioral changes, such as increased intake of fatty and salty foods and sedentary behavior [5]. Biological and behavioral risk factors formed during adolescence tend to persist into adulthood [6]. A 6-year retrospective study of evaluating anthropometric data found that high school students’ high BP persisted into their university years [7]. A better understanding of the causes of high BP among adolescents is needed, especially on modifiable lifestyle factors. This will help health professionals develop appropriate interventions against high BP among adolescents. The etiology of the elevating BP among adolescents has been evolving and is multifaceted. The National Heart, Lung and Blood Institute Growth and Heart Study reports that overweight and obesity contribute to high BP levels among adolescents [8]. Evidence is abundant in the literature that indicates body mass index (BMI) is positively associated with high systolic BP [9,10]. A prospective study of McGavock et al. (2007) [10] demonstrates that BMI increase is associated with the trajectory of high systolic BP. Specifically, students showing a larger increase in BMI over a 2-year period were more likely than their counterparts to have higher values of systolic BP, in spite of similar systolic BP and BMI levels at baseline. Although the relationship of systolic BP with BMI has been well established, the association between diastolic BP and BMI is still inconclusive [11,12]. Lifestyle factors, including sedentary behavior, physical activity (PA), and unhealthy dietary habits, are noted as major contributing factors to high BP. A longitudinal study of 4,552 Brazilian adolescents found that increased television (TV) viewing is associated with high systolic BP and diastolic BP levels [13]. By contrast, a cross-sectional study of a European population-based sample did not find substantial associations between TV viewing and either systolic BP or diastolic BP in children and adolescents [14]. Similarly, PA has an inconclusive relationship with BP. Some studies found a positive association [15], whereas others found no relationship [12]. In addition to physical inactivity, undesirable dietary habits have been associated with high BP among adolescents. High sodium intake [16], skipping breakfast [17], and consumption of fast foods [18] have been shown to increase the risk of abnormal BP. However, most of the aforementioned studies that examined BP during adolescence employed cross-sectional design in which causal inferences cannot be established. Furthermore, few studies have examined determinants of systolic BP and diastolic BP separately using a longitudinal prospective cohort of adolescents in a school setting. The HEROES (Healthy, Energetic, Ready, Outstanding, Enthusiastic Schools) Initiative is a grant-funded, multilevel intervention intended to facilitate environment changes within schools by implementing the coordinated school health (CSH) approach, designed by the U.S. Centers for Disease Control and Prevention (CDC) to decrease childhood obesity and increase healthy life habits for students, their families, and school staff [19]. CDC endorsed a CSH approach as a practical guidance of school-based intervention to promote lifelong healthy eating and PA. Because
of the complex of ecology web in a school setting, this model emphasizes the integration of multiple components (i.e., curriculum, food service, and physical education classes) and multiple levels (i.e., family and communities) for the achievement of school-based intervention program [19]. Among the eight components of the CSH approach, the HEROES Initiative focuses on the five most relevant to the prevention of childhood obesity: health education, nutrition services, physical education, health promotion for staff, and family and community involvement. The HEROES Initiative has innovative and unique facets differentiating from the other school-based interventions. First, it delivers extensive infrastructure that includes local oversight, substantial financial and technical supports, and specific implementation strategies that are designed to fit schools’ individual needs and identities. Second, although the CSH-based interventions are typically implemented at the district level [20], the HEROES Initiative is implemented at the individual school building level. Third, the rigorous evaluation framework is included in the Initiative by conducting an annual assessment to develop program enhancement and increase the likelihood of intervention’s success. The purpose of this study was to examine the effectiveness of the HEROES Initiative, a multicomponent school-based obesity prevention intervention, in improving systolic BP and diastolic BP over a period of 18 months in high school students. Additionally, this study assessed long-term predictors of systolic BP and diastolic BP changes. It was hypothesized that the HEROES Initiative would have a positive effect on systolic BP and diastolic BP improvement. It was also hypothesized based on previous findings in the literature that lifestyle factors, such as TV viewing, PA, and eating habits, are significant predictors for both types of BP increases. Methods Participants A total of 847 9the11th graders from three high schools in Southern Indiana who participated in the HEROES Initiative composed the sample for this study. School wellness coordinators, nurses, and nursing students from local colleges took students’ physiological measurements, including height, weight, systolic BP and diastolic BP at baseline (fall 2009), 6 months (spring 2010), 12 months (fall 2010), and 18 months (spring 2011). Concurrently, students completed Student Health Assessment Questionnaire, an online survey developed for the Initiative, which includes questions related to dietary habits, PA, and sedentary behaviors of individual students. Almost all the question items were adopted from the already validated Schools Physical Activity and Nutrition Survey Questionnaire [21]. Detailed information about school sampling and the questionnaire can be found elsewhere [22]. The study protocol was approved by the investigators’ institutional review board. Anthropometric and blood pressure measurements Students’ height and weight were measured by trained staff using a stadiometer and a digital scale, respectively, at each survey time point. BMI was computed based on measured height and weight (kg/m2). Using the BMI percentiles for sex and age suggested by the CDC growth charts, participants were categorized into four groups: underweight ( .05). Students who were overweight or obese, nonwhites, those who spent more time on watching TV, those who were enrolled in free or reduced-price lunch, those who usually skipped breakfast, and those who ate supersize meals when eating fast food showed a higher proportion of hypertension than normotensive students at the end of the intervention (p values < .05). In Table 2, the results of sequential GEE analyses for systolic and diastolic BP are presented. In model 1, both systolic and diastolic BP significantly decreased with time (p values < .0001), whereas both systolic and diastolic BP increased with quadratic time (p values < .0001), indicating that the mean of both BP rapidly decreased from baseline to 6 months, then smoothly decreased and even increased a bit later. The mean of systolic and diastolic BP, respectively, was 115.3 mm Hg (SD ¼ 10.3) and 66.7 mm Hg (SD ¼ 7.0) at 6 months, 116.4 mm Hg (SD ¼ 10.3) and 67.7 mm Hg (SD ¼ 7.0) at 12 months, and 116.7 mm Hg (SD ¼ 10.5) and 68.2 mmHg (SD ¼ 7.2) at 18 months. When demographic variables were entered (model 2), BMI increases were significantly associated with increases of both systolic and diastolic BP (p values < .0001), whereas being male only predicted systolic BP (p values < .0001) not diastolic BP increases. When activity-related variables were entered (model 3), increases in time spent on TV viewing significantly predicted systolic BP and diastolic BP increases (p values < .05), although changes in MPA and VPA showed no significant effects on systolic BP and diastolic BP changes. In model 4, eating-related variables were entered into model 3. Even after controlling for all the time, demographic, and activity-related variables, increases in french fries or chips consumption and skipping breakfast predicted systolic BP increases (p values < .05) but not diastolic BP increases. Increases in the frequency of having supersize fast
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Table 1 Select characteristics of normotensive and hypertensive adolescents who were exposed to the HEROES Initiative Characteristic
Total sample Fall 2009 (n ¼ 847)
Hypertension, % Age, years, mean (SD) 14.9 (.4) BMI, kg/m2, mean (SD) 23.5 (5.5) Sex, % (SE) Male 50.4 (1.7) Female 49.6 (1.7) Race, % (SE) Nonwhite 21.4 (1.4) White 78.6 (1.4) Lunch status, % (SE) Paid 57.9 (1.7) Free or reduced 42.1 (1.7) Weight status, % (SE) Underweight or normal 64.4 (1.6) Overweight 16.3 (1.3) Obese 19.3 (1.4) MPA, % (SE) 0 day 15.4 (1.7) 1e5 days 63.6 (2.2) 6e7 days 20.9 (1.9) VPA, % (SE) 0 day 4.8 (1.0) 1e5 days 68.0 (2.1) 6e7 days 27.2 (2.0) TV viewing, % (SE)
