EAL

NGHC: Prevention of Chronic Disease (2013)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To evaluate the effects of a three-year school-based program on risk factors for diabetes in children followed from sixth grade through eighth grade.

Inclusion Criteria:

For schools:

At least half of the children in the school must be eligible for federally subsidized free or reduced-price meals
At least half of the student population must be black or Hispanic.

Students were included if:

They were enrolled in sixth grade in the fall of 2006
Their height, weight, sex and age were recorded at baseline
They did not have diabetes or any condition precluding regular participation in physical education.

Exclusion Criteria:

For schools:

Fewer than half of the children in the school were eligible for federally subsidized free or reduced-price meals
Less than half of the student population was black or Hispanic.

Students were excluded if:

They were not enrolled in sixth grade in the fall of 2006
Their height, weight, sex and age were not recorded at baseline
They had diabetes or any condition precluding regular participation in physical education.

Description of Study Protocol:

Recruitment

42 schools at seven field sites were recruited based on inclusion criteria.

Design

Randomized, cluster-design was used for this study. Schools were the unit for randomization, intervention and analysis. At seven different field sites across the United States, 21 schools were randomly assigned to be the control group and 21 schools were assigned to receive the intervention.
Students beginning sixth grade in fall 2006 had fasting measurements recorded for height, weight, waist circumference, blood pressure, glucose level and insulin level. Measurements were taken by trained study staff personnel not involved in the intervention.
For the next three school years, students at the intervention schools received the four-component intervention, comprised of nutrition, physical activity, behavioral knowledge and skills and communications and social marketing. Unannounced, structured observations were conducted randomly during each semester to assess the extent to which the intervention was implemented as planned. The same fasting measurements were again taken when the students were finishing eighth grade in the spring of 2009.

Intervention

The intervention at assigned schools consisted of nutrition, physical activity, behavioral knowledge and skills, and communications and social marketing. The nutrition component focused on the quantity and nutritional quality of foods and beverages served throughout the school environment. The physical education component aimed to increase time spent in moderate-to-vigorous physical activity, defined as any activity raising heart rate to 130 beats per minute or more.
A classroom-based program, FLASH (Fun Learning Activities for Student Health), was used to communicate behavioral knowledge and skills to target self-awareness, knowledge, behavioral skills such as goal setting and peer involvement for behavioral change. Social marketing and communication strategies supported the intervention.

Statistical Analysis

General linear mixed models were used to analyze differences between intervention and control schools. Covariance structure was used to adjust for variability both between schools and within students in the same school. The authors estimated that 36 schools were needed to sample in order to have a 90% power at a significance level of 0.05. Data were analyzed only for students with both measurements, from fall 2006 and spring 2009.

Data Collection Summary:

Timing of Measurements

Fasting measurements (weight, height, waist circumference, blood pressure, glucose level and insulin level) were taken at the schools in the fall of 2006 and again in the spring of 2009, by trained study staff not involved with the intervention.

Dependent Variables

Primary outcome: Combined prevalence of overweight and obesity, defined as Body Mass Index (BMI) at the 85th percentile or higher
Secondary outcomes:
- Obesity (BMI at the 95th percentile or higher)
- BMI Z-score
- Continuous and categorical measurements of waist circumference, fasting glucose and fasting insulin.

Independent Variables

Four integrated components comprised the intervention:

Nutrition
Physical activity
Behavioral knowledge and skills
Communications and social marketing.

Control Variables

Random, unannounced structured observations were done during each school semester to assess the extent to which the intervention was being implemented as planned. Strategies were implemented:

90±5.6% of the time for nutrition
87±4.9% of the time for physical education
97±4.8% of the time for FLASH activities
84±9.1% of the time for hanging posters as part of the communications campaign.

Description of Actual Data Sample:

Initial N: 6,358 students were assessed at the beginning of sixth grade, in fall 2006
Attrition (final N): 4,603 (47.3% male; 72.4% of initial N) were reassessed at the end of eighth grade, in spring 2009
Age: At baseline, students were 11.3±0.6 years old.

Ethnicity

Students having measurements taken in both fall 2006 and spring 2009 were:

54.2% Hispanic
18.0% black
19.3% white
8.5% other.

Other Relevant Demographics

Both intervention and control groups had similar levels of highest education attained by head of household, as well as similar family history of diabetes.

Anthropometrics

At baseline, both intervention and control groups were fairly matched on:

Percentage of students with BMI 85th percentile or more
Percentage of students with BMI 95th percentile or more
BMI Z-score
Waist circumference in the 90th percentile or higher
Waist circumference in centimeters
Percent of students with fasting insulin 30 units per ml or more
Fasting insulin in units per ml
Percent of students with fasting glucose 100ml or more per dL
Fasting glucose in ml per dL.

Location

Seven different field centers across the United States; specific locations not mentioned.

Summary of Results:

Key Findings

Both the intervention and control schools had reductions in the prevalence of overweight and obesity (BMI 85th percentile or higher), without significant difference between the groups. There was a nearly significant reduction in the intervention schools for prevalence of obesity (BMI 95th percentile or higher; P=0.05).
Mean BMI z-score and the percentage of students with waist circumference 90th percentile or higher were significantly lower in the intervention schools (P=0.04 for both)
Students in intervention schools had 19% lower odds of being obese at the end of the study than did those in control schools (OR, 0.81; 95% CI: 0.66 to 1.00; P=0.05)
Both the intervention and control schools had significant and nearly identical decreases in the prevalence of overweight and obesity (15.9% in control schools, 16.5% in intervention schools)
Overweight or obese students in intervention schools had 21% lower odds of being obese at the end of eighth grade (OR, 0.79; 95% CI: 0.63 to 0.98; P=0.04)
Intervention schools had a significantly lower percentage of students with waist circumferences at or above the 90th percentile at the end of the study (P=0.03)
Students in intervention schools had significantly lower mean insulin levels in eighth grade than did students in control schools (P=0.04).

Variables	Intervention Schools	Control Schools	Statistical Significance of Group Difference
Body Mass Index 85th percentile or more (percent of students)	45.8	45.2	P=0.92
BMI 95th percentile or more (percent of students)	24.6	26.6	P=0.05
BMI z-score	0.85±1.03 (0.12 to 1.63)	0.86±1.05 (0.16 to 1.70)	P=0.04
Waist circumference 90th percentile or more (percent of students)	21.3	22.7	P=0.04
Waist circumference (cm)	80.6±14.8 (69.3 to 88.3)	81.0±14.8 (70.0 to 89.2)	P=0.07
Fasting insulin (U per ml)	16.9±15.4 (9.2 to 19.8)	17.4±13.4 (9.4 to 20.5)	P=0.04
Fasting glucose (mg per dL)	93.5±8.6 (88.0-98.0)	94.3±7.9 (89.0-99.0)	P=0.33

Author Conclusion:

There was not a significant effect of the comprehensive school-based program on the combined prevalence of overweight and obesity. However, the intervention was associated with significantly greater reductions in various indexes of adiposity, including the BMI Z-score, the percentage of students with waist circumference in the 90th percentile or higher and the mean insulin level in the overall sample. These changes may reduce the risk of childhood-onset type 2 diabetes.
The intervention was also associated with a significant decrease in the prevalence of obesity in the sub-group of students who were overweight or obese at the beginning of the study and approached significance in the full sample of students.

Funding Source:

Government:

NIDDK of NIH to the Studies to Treat or Prevent Pediatric Type 2 Diabetes (STOPP-T2D) collaborative group

Not-for-profit

American Diabetes Association

Reviewer Comments:

Limitations of this study discussed by the authors include:

Lack of a nationally representative sample (due to intentional over-sampling of low-income black and Hispanic students)
Inability to assess the feasibility, effectiveness or sustainability of an intervention program outside a study setting, as this was an efficacy study.

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?	No
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?	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.)	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?	Yes
	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?	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.)	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?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	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?	N/A
	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?	N/A
	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)?	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?	Yes
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