Pediatric Weight Management

PWM: School-based Programs to Prevent Overweight (2006)

Citation:

Ritenbaugh C, Teufel-Shone NI, Aickin MG, Joe JR, Poirier S, Dillingham DC, Johnson D, Henning S, Cole SM, Cockerham D. A lifestyle intervention improves plasma insulin levels among Native American high school youth.  Prev Med 2003;36:309-19. 

 
Study Design:
Non-Randomized Controlled Trial
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

The primary purpose of the Zuni Diabetes Prevention Program is to reduce NIDDM risk factors among Zuni high-school-age youths.  Purpose of paper is to provide selected results for the first 4 years of the project that are among the first to indicate that the increase of type 2 diabetes is not inevitable.

Inclusion Criteria:
Not described
Exclusion Criteria:
Not described
Description of Study Protocol:

Recruitment:

School-wide announcements, in-class announcements and flyers at high school wellness center.

Program components:

  1. School food supply modification: Sugar-free (diet) beverages in vending machines (to replace 4 regular soft drink machines); water coolers installed (previously only unpalatable water high in sulfur and iron from the local aquifer was available), healthy snacks and sugar-free beverages sold by wellness center; work with school food service to increase fruits and vegetables and decrease fat in school lunches)
  2. School classroom education: 9 weeks of PE class devoted to orientation to wellness center and diabetes prevention (all 160 students in 1995-1997?); biology class learning units (60 students in 1995-1997); food service class learning unit (24 students in 1997); in class posters, informative displays, school announcements and public service announcements for local radio station
  3. School wellness center: outfitted with exercise equipment including weights, treadmills, exercise bikes, and a climbing wall; sponsored activities outside the facility including aerobics classes, basketball tournaments, hiking, rock climbing, running camp and races, mountain biking, and dances; staffed by 4-6 adults and student certified Community Fitness Instructors; open weekdays during lunch and after school (until 8:00 PM) and available at other times as well.

Measurements: 

Multiple cross-sectional measures of willing 11th & 12th graders at baseline (year 0), 1.5 y, and 3 y (no individual measured more than once – true for plasma glucose and insulin, not specified for anthropometry measures).

Statistical Analysis:

  • Primary outcome measures used in analysis were either the median or the 75th percentile of the distribution – because insulin data in year 0 were truncated, distributions tended to be positively skewed and greatest physiologic effects are likely to be found at the upper ends of the distributions
  • Regression analysis for percentile of distribution (quintile regression) – to test the time trend over 3 y of intervention
  • Multivariate analyses for diabetes outcomes – to test effects of gender, family history and BMI
  • Student’s t test – for comparison of Zuni and Anglo values
Data Collection Summary:

Dependent Variables:

  • Biologic endpoints - Plasma insulin & glucose after an 8-h fast and 30 min after a 75-g glucose load (modified OGTT)
  • Body composition - BMI (measured wt and ht)

Other:

  • Family history of diabetes – Questions (3) on whether mother, father or other close relatives have DM; each ‘yes’ is scored as ‘1’
  • Environmental change indicators – Soft drink vending machine sales, number of individuals (students, staff & community members) visiting wellness center per day

Independent:

  • Zuni Diabetes Prevention Program (see above)

Control Variables: 

  • separate analyses by gender
Description of Actual Data Sample:

Original Sample: ˜125 junior and senior students available at high school

Withdrawals/Drop-Outs:  reasons all students in school were not measured is not fully discussed (in year 3, 35 otherwise eligible students were attending a vocational school off the reservation, but details on other students and during other years not provided); 7 Zuni youth (3 in year 0, 3 in year 1.5 and 1 in year 3) who had elevated fasting glucose levels were excluded from analyses and given referral for further evaluation

Final Sample: 70 Zuni adolescents in year 0 (mean age 17.2 y), 64 Zuni in year 1.5 (mean age 17.2 y), 65 Zuni in year 3 (mean age 17.5 y), 37 comparison Anglo adolescents (mean age 17.1 y)

11th – 12th grades (data on younger students not included in this manuscript); represents >60% of the eligible junior and senior students on Zuni campus in all 3 years

Location: Zuni Pueblo, Indian reservation, New Mexico (population 10,000); 1 high school (enrollment ˜400)

Duration:  3 school y (spring 1994- spring 1997)

Race/Ethnicity:  100% Zuni Native American

SES:  Not described

Concurrent ANGLO Comparison Group: 38 youth, 17-19 y, with no Latino or Native American heritage from a single high school without any intervention in Tucson; 2 cohorts recruited simultaneously with the 1.5 and 3 year evaluations and none had abnormally high glucose levels

Summary of Results:

BMI:

  • No significant differences over 3 years among Zuni students
  • No significant differences between Zuni students at any year and Anglo students

Family history:

  • No differences in family history of diabetes I the 3 years or between Zuni and Anglo females
  • Anglo males reported significantly less family history of diabetes than Zuni males

Wellness center use:

  • Year 1 – mean of 34 students per day or 8.5% of total high school population used wellness center
  • Year 3 – corresponding numbers increased (significance not indicated) to mean of 133 students or 28%

Beverage sales:

  • Baseline – 24 oz/student per week of sweetened soft drinks purchased at school
  • Year 3 – 0 purchased (and anecdotal evidence that not bringing from home)

Plasma glucose and insulin:   

  • Fasting & 30-min glucose levels
  • normal at baseline for Zuni (n=72) and Anglo (n=37) youth
  • did not significantly change throughout the study (though trend toward decrease) (year 3 n=55?)
  • Fasting and 30-min insulin levels
    • significantly elevated for Zuni youth at baseline (p=?) compared to Anglo youth
    • showed significant steady declines for both males and females throughout the study (p = .06 to p=.000 for trends), particularly for the 30-min post-glucose challenge levels
    • at year 3 no longer elevated for Zuni vs. Anglo males; attenuated but still elevated for Zuni vs. Anglo females
    • Became less strongly related to BMI and to family history over period of intervention
Author Conclusion:

Among at-risk youth, an environmentally based lifestyle intervention may significantly suppress markers of type 2 diabetes risk.

In demonstrating a positive response among high school youth to a type 2 diabetes primary prevention intervention project that targeted the environment plus education, the data presented here are among the first to indicate that through reasonable changes at the community level, the consequence may not be inevitable.
Funding Source:
Government: NIDDK, NIH, Indian Health Service, National Center for Genome Research, IHS Zuni Diabetes Project
In-Kind support reported by Industry: Yes
Reviewer Comments:

Strengths:

  • 3 year, multi-component trial.

Limitations: 

  • Suitability of Anglo group for comparison not established,
  • comparison of year 1 and year 3 groups not controlled for potential confounders  & limited comparison of differences between groups,
  • inclusion and/or exclusion criteria not provided,
  • no diet or physical activity evaluation of individuals,
  • unclear sample size for various analyses,
  • healthy youth may be more likely to volunteer and be overrepresented,
  • no control for potential confounders (e.g., participation at wellness center, dietary changes)

Other Comments:

Confusing referral to study as both a 3- and a 4-year intervention (initial year for planning?).
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? ???
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? ???
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes