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

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • To describe a school and community intervention project that includes intergenerational and other culturally appropriate activities designed to promote exercise and a healthful diet
  • To present descriptive data on obesity of fifth grade Navajo and Pueblo children from rural schools.
Inclusion Criteria:

Navajo and Pueblo fifth-grade children from 11 rural elementary schools in central and northwestern New Mexico, ranging from nine to 13 years old.

Exclusion Criteria:

None specified.

Description of Study Protocol:

Three schools were randomly assigned to the first intervention group (cardiovascular curriculum), four schools were randomly assigned to the second intervention group (cardiovascular curriculum with social influences component) and four schools were randomly assigned to a control condition (no intervention for the  first three years, but phased in as curriculum schools during the last two years of the project).

All student received the same pre-test and post-test protocol for all five years of study. 

Intervention included a fifth-grade multifactorial, comprehensive curriculum developed to increase knowledge and lead to health behavior changes; prevention activities designed to be culturally relevant to rural Native American children in Southwest.

Curriculum divided into five teaching units: Cardiovascular system, exercise, nutrition, tobacco and social influences (for one of the intervention groups). Each unit included activities from each of three domains: Knowledge, attitudes and behaviors.

Members of the community were included in many activities: Videotapes were shared with elders at senior citizen centers and materials were developed and sent home to families. Other activities included presentations on parent days, community health fairs and fitness competitions for adult school staff.

All students enrolled in the seven intervention schools were taught one of the cardiovascular health promotion curricula during one semester between September 1988 and February 1993. In the final two years, all students from all 11 schools received the curriculum with the social influences component. General procedure included a session of pre-testing, 18 hours of curriculum supplemented by community activities and a session of post-testing.

Measurement Handbook for Pre- and Post-testing was developed as training guide and reference to ensure standard protocol.

Surveys were completed by all students in a class at one time; each question was read aloud twice to allow ample time and accommodate students with low reading skills.

Data Collection Summary:

Dependent Variables

  • Health knowledge (using a 60-item knowledge questionnaire)
  • Attitudes (using a 21-item survey regarding attitudes towards obesity perceptions and feelings about weight)
  • Behaviors (using separate surveys to determine self-reported behaviors related to food, tobacco and exercise habits)
  • Height
  • Weight
  • BMI (compared to NHANES II reference data); tricep skinfold thickness (using Slimglide calipers).

Independent Variables

  • Full curriculum (cardiovascular and social influences) for five years
  • Cardiovascular curriculum in the first three years, then curriculum with social influences component in the final two years
  • No curriculum in the first three years, then curriculum with social influences component in the final two years.
Description of Actual Data Sample:
  • Original Sample: 12 schools
  • Withdrawals and drop-outs: One school dropped out due to very small class enrollment
  • Final sample: 1,543 Navajo and Pueblo children from 11 rural elementary schools (779 girls, 764 boys)
  • Location: Central and northwestern New Mexico
  • Ethnicity: 770 Navajo, 773 Pueblo (50% from each tribe).
Summary of Results:

Preliminary results show significant increase in overall knowledge for students in intervention schools (N=674) when compared to control schools (N=375). Self-reported measure of exercise habits shows significant increase in exercise for students in intervention schools compared to students in control schools. When self-reported eating habits were compared, intervention students showed significant decrease in use of butter on bread or tortillas from pre-test to post-test compared to control students.

36% boys and 33% girls had BMI greater than 85th percentile; there were no significant differences between tribal groups. When compared by tribe, significantly more Pueblo natives had BMI greater than 85th percentile than Navajo natives.

Correlation of pre-test BMI and skinfold measurements was R=0.84 (P<0.001).

When student perceptions of their own body size were compared to BMIs, there were no significant differences between tribes or between boys and girls. Of students who said they were “a lot too fat,” 85% had BMI greater than 85th percentile; 70% of students who said they were “about right” were between 15th and 85th percentile.

Author Conclusion:

A substantial number of Navajo and Pueblo boys and girls from study population were overweight when compared to NHANES II reference standards; Pueblo boys and girls had significantly higher BMIs than Navajo students.

A strong correlation between BMIs and tricep skinfold measurements indicated that students with high BMIs compared to NHANES II data were in fact overweight.

Most of the children had accurate perception of themselves.

Increase in health knowledge and positive changes in eating habits and exercise patterns found in the study suggests a primary prevention program, including culturally relevant curricula grounded in health promotion theory is an effective approach for the American Indian population.

Funding Source:
Government: NHLBI: National Heart Lung and Blood Institute
Reviewer Comments:

Limitation: No measure of adiposity resulting from intervention, only descriptive data was discussed.

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? No
  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) Yes
  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? N/A
  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.) N/A
  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? Yes
  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%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  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? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  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? Yes
  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? No
  6.6. Were extra or unplanned treatments described? No
  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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  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? No
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