Abstract
Purpose:
The aim of this study was to examine changes in systolic blood pressure (SBP) and whether physical activity and obesity status predicted SBP change for African-American adolescents (n=181) participating in a behavioral weight control trial.
Methods:
Data were collected at baseline, 7-months (end-of-treatment), and 9-months (2-month follow-up).
Results:
Nearly half of adolescents achieved clinically significant SBP reductions at 7 and 9 months. Significantly fewer adolescents had elevated SBP at 7 and 9 months compared to baseline (both p<.001). Changes in percent overweight and moderate-to-vigorous activity predicted changes in SBP over time.
Conclusions:
Obesity reduction and increases in moderate-to-vigorous physical activity may predict short-term, clinically meaningful reductions in SBP for African American adolescents with obesity.
Introduction
Adolescents with obesity are 2.2-4.5 times more likely to develop hypertension during adolescence and early adulthood than teens who are of a normal weight;1 this is especially alarming for African American adolescents given their greater lifetime risk for hypertension.2 Guidelines encourage adolescents to engage in 60 minutes of moderate-to-vigorous activity (MVPA) daily to prevent hypertension and obesity.3,4 In a recent meta-analysis,5 physical activity (PA) demonstrated a moderate decrease in systolic blood pressure (SBP; M=0.60) and obesity (M=0.47) in 10-19 year-olds with overweight and obesity.5 Further, mean SBP change across trials (−7.1 mm Hg) exceeded that reported in a meta-analysis of medication therapy in hypertensive adults (−.6.77 mm HG).6 Whether these findings extend to African American adolescents is unclear, however, given their underrepresentation in the trials reviewed. The current secondary data analysis begins to address this significant gap by examining 1) changes in SBP and 2) MVPA and percent overweight as predictors of SBP change in African American adolescents participating in a sequential multiple assignment randomized trial (SMART) of behavioral intervention strategies to address obesity (ClinicTrials.gov identifier: NCT01350531).
Methods
Full details of trial methodology and enrollment/recruitment7 are reported elsewhere. Inclusion criteria were (a) English-speaking families self-identifying as African-American and living ≤30 miles of the medical center and (b) adolescents aged 12-16 with body mass index ≥ 95th percentile (obese). Exclusion criteria were (a) obesity secondary to medication or chronic condition, (b) medical conditions preventing participation in normal exercise, and (c) pregnancy. Baseline sample characteristics of the 181 families included for analysis are presented in Table 1. Caregivers provided written consent and adolescents gave written (≥13 years) or verbal assent. The trial protocol was approved by the Wayne State University Institutional Review Board.
Table 1.
Descriptive statistics [mean (SD) or % (n)] for sample characteristics at baseline and independent and dependent variables of interest across time
| Baseline (N=181) |
7-months (N=181)c |
9-months (N=181)c |
|
|---|---|---|---|
| Sociodemographic Variables | |||
| Adolescent | |||
| Age (y)a | 14.26 (1.45) | - | - |
| Femalea | 67.4% (122) | - | - |
| Executive functioninga | 123.77 (27.70) | - | - |
| Depressiona | 6.47 (6.50) | - | - |
| Caregiver | |||
| Age (y) | 42.96 (7.96) | - | - |
| Female | 95% (172) | - | - |
| Single | 63.5% (115) | ||
| Body Mass Indexa | 40.97 (10.16) | ||
| Systolic Blood Pressure (mm Hg)a | 130.49 (16.97) | ||
| Median Family Annual Incomeb | $12,000-$15,999 | ||
| Independent and Dependent Variables of Interest | |||
| Adolescent Percent Overweight | 96.81 (37.59) | 93.68 (39.46) | 93.79 (39.10) |
| Adolescent Systolic Blood Pressure (mm Hg) | 121.33 (10.20) | 121.74 (10.10) | 121.33 (9.80) |
| Moderate-Vigorous activity (h x wk) | 3.12 (3.18) | 2.33 (3.18) | 2.03 (2.17) |
SD, standard deviation.
Covariates in regression models.
Interquartile range: $5,000-$11,999 to $25,000-$34,999.
Missing data estimated using the expectation-maximization algorithm (SPSS).
Consistent with SMART methodology, families (n=181) were randomized twice. In Phase 1 (P1), families were randomized to two weekly sessions of home- or office-based cognitive-behavioral skills training delivered using motivational interviewing communication strategies. Session 1 (60-90 minutes, face-to-face) focused on teaching empirically supported weight management skills (e.g., self-monitoring and stimulus control). Session 2 (15-45 minutes; via phone for officenbased) was a check-in to problem-solve barriers to skill implementation. Adolescents’ PA goals were 60 minutes of cardio activity (working up to at least moderate intensity) three times per week and lifestyle plus other activities on all other days of the week. Self-monitoring and cue modification to support PA were also encouraged. In Phase 2 (P2), treatment responders (≥3% weight loss) received weekly relapse prevention sessions (60 minutes; face-to-face) in their P1 setting. Non-responders (<3% weight loss) were re-randomized to home-based continued skills (CS) or contingency management (CM). CS families repeated P1 sessions or focused on additional needs (e.g., emotional eating). In CM, adolescents earned points for weight loss and caregivers for treatment attendance. CS and CM dose replicated P1.
Assessments were conducted at baseline, 7 months (end-of-treatment), and 9 months (2-month follow-up). At each assessment, research staff measured adolescent blood pressure (BP), height (centimeter), and weight (kilogram), and adolescents self-reported frequency and intensity (light, moderate, hard, or very hard) of PA for 3 days using the Previous Day Physical Activity Recall.8 At baseline, caregivers reported on family sociodemographic characteristics and adolescent executive functioning (Behavior Rating Inventory of Executive Function–Parent Report; Global Executive Composite);9 adolescents reported on depression (Patient-Reported Outcome Measurement Information System—Pediatric Short Form v1.0–Depressive Symptoms).10
Changes in SBP were evaluated from baseline to 7 and 9 months in two ways: 1) difference in the percentage of adolescents with elevated BP (eBP; SBP≥120), and 2) difference in the percentage of adolescents achieving a clinically significant reduction in SBP (−2mm HG).2 Generalized estimating equation, following the SMART procedure outlined by Nahum-Shani et al,11 was used to examine whether changes in adolescent percent overweight and MVPA predicted changes in SBP (mm HG) from baseline to 7 and 9 months. Caregiver body mass index and SBP and adolescent age, sex, executive functioning (moderator of weight outcomes in parent trial),7 depression (associated with physical activity and obesity during adolescence),12 MVPA, and treatment assignment were entered as covariates. All analyses were conducted using SPSS version 25.0 (SPSS Inc., Chicago, IL).
Results
Table 1 summarizes the dependent and independent variables of interest across time. At 7 months, 19% (n=19) of the 98 adolescents with eBP at baseline were normal BP (nBP; SBP<120 mm HG; χ2(1) = 26.13, p<.001) and 44% (n=73) of all adolescents achieved a clinically significant SBP reduction (M = −7.64 ± 5.38 mm HG). By 9 months, 28% (n=29) of adolescents with eBP at baseline were nBP (χ2(1) = 26.13, p < .001) and 45% (n=76) of all adolescents achieved a clinically significant reduction in SBP (M= −8.11 ± 5.35 mm Hg).
In the generalized estimating equation model (Table 2), both MVPA and percent overweight emerged as significant predictors of adolescent SBP after controlling for the effects of caregiver SBP and adolescent age and sex. Specifically, greater increases in adolescent MVPA (B = −0.28) and decreases in weight status (B = 0.09) were associated with greater decreases in SBP. Further, lower SBP was associated with lower caregiver SBP (B = 0.11), younger adolescent age (B = 1.09), and female sex (B = 4.56).
Table 2.
Generalized estimating equations analysis of MVPA and percent overweight on SBP in African American adolescents receiving obesity treatment
| Variable | B | Wald Chi Square |
df | p |
|---|---|---|---|---|
| Intercept | 86.30 | 133.15 | 1 | <.001 |
| Time | −0.12 | 0.07 | 1 | .797 |
| Adolescent baseline age | 1.09 | 7.81 | 1 | .005 |
| Adolescent gender (femalea) | 4.56 | 11.61 | 1 | .001 |
| Caregiver baseline BMI | −0.04 | 0.43 | 1 | .514 |
| Caregiver baseline SBP | 0.11 | 8.64 | 1 | .003 |
| Adolescent executive functioning | −0.02 | 1.26 | 1 | .262 |
| Adolescent depression symptoms | −0.15 | 2.09 | 1 | .149 |
| Initial treatment (homea vs. office) | 0.68 | 0.17 | 1 | .679 |
| Secondary treatment (CSa vs. CM) | 1.02 | 0.52 | 1 | .472 |
| Initial treatment * secondary treatment | 0.28 | 0.02 | 1 | .900 |
| Time * initial treatment | 0.76 | 1.43 | 1 | .232 |
| Time * secondary treatment | −0.09 | 0.02 | 1 | .889 |
| Time * initial treatment * secondary treatment | −1.06 | 1.26 | 1 | .262 |
| MVPA | −0.28 | 4.14 | 1 | .042 |
| Adolescent percent overweight | 0.09 | 31.49 | 1 | <.001 |
BMI, body mass index; CM, contingency management; df, degrees of freedom; CS, continued skills; MVPA, moderate-to-vigorous physical activity; SBP, systolic blood pressure.
The reference group
Discussion
This study provides some of the first data on SBP changes and whether PA and obesity reduction predict SBP changes in treatment-seeking African American adolescents with obesity. Nearly 20% of adolescents with eBP at baseline were nBP by the end of treatment; this number increased to almost 30% at the 2-month follow-up. Close to half of adolescents achieved clinically meaningful reductions in SBP by end of treatment (44%) and 2-months post-treatment (45%). SBP changes for this subgroup exceeded those reported in a recent meta-analysis of PA interventions in obese youth.5 This finding is noteworthy given our study specifically targeted a high-risk sample of adolescents. Further, teens changed PA at their own pace and in their natural environment compared to the structured, supervised PA programs tested in previously published trials. Our models also suggest small changes reductions in obesity and increases in MVPA are modifiable predictors of short-term reductions in SBP. Collectively, our findings support the need for future research to further examine the dose-response relationship of PA on cardiovascular and anthropometric outcomes in high-risk youth with obesity.13 A larger sample, longer-term follow-up, and use of objective measures of PA (e.g., accelerometry) will be important components of this next phase of research.
Implications and Contributions.
Outcomes are preliminary but suggest small reductions in obesity and increases in moderate-to-vigorous physical activity may impact cardiovascular health in African American adolescents via reduced systolic blood pressure.
Acknowledgements:
Outcomes described in this manuscript were presented at the 2017 Annual Meeting of the Obesity Society. Dr. Naar is now at Florida State University School of Medicine.
Funding Sources:
This work was supported by the National Heart, Lung, and Blood Institute and the Eunice Kennedy Shriver National Institute of Child Health and Human Development (U01HL097889). The National Institutes of Health had no role in the study design; data collection, analysis, or interpretation; writing of the manuscript; or the decision to submit the manuscript.
Footnotes
Disclaimer: The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. S.N. is now at Florida State University School of Medicine, Tallahassee, Florida.
Conflicts of Interest: The authors have no conflicts of interest to declare.
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