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Citation:

Prell HC, Berg MC, Jonsson LM, Lissner L. A school-based intervention to promote dietary change. J Adolesc Health. 2005 Jun; 36(6): 529.


PubMed ID: 15909359
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
NEUTRAL: See Research Design and Implementation Criteria Checklist below.
Research Purpose:

To determine the effect of school lunch modifications and increased education about the health benefits of fish on adolescent consumption of fish and knowledge about fish.

Inclusion Criteria:

Inclusion criteria included eighth grade students at three comprehensive schools in Sweden. It also included the following:

  • Students were approximately 14 years old
  • Characteristics of the schools were similar (for student numbers, socioeconomic levels, kitchen facilities, food service systems, willingness of faculty and staff to participate)
  • All students were enrolled in home economics courses at the time of the study.

 

Exclusion Criteria:
  • Students not in eighth grade
  • Students not enrolled in home economics courses.

 

Description of Study Protocol:

Recruitment

  • Schools were selected based upon similar characteristics (number of students, socioeconomic levels, kitchen facilities, serving systems) and willingness of faculty and staff to participate
  • No other recruitment information was provided. 

Design

Randomized control trial.

Dietary Intake/Dietary Assessment Methodology

Consumption of fish was measured through direct observation in the school canteen when the fish was served. This was done once a week (five times) during the study period.

Intervention

Two interventions were developed through a previous pilot study:

  • The School Lunch Intervention (SL): Focused on the preparation and appearance of the   fish meals, on extending the choice and on marketing the fish meals
  • The School Lunch Intervention + Home Economics Intervention (SL + HE): Focused on the same characteristics of the SL intervention and included lessons about fish and nutrition along with classroom cooking experiences. 

Statistical Analysis

  • Differences in baseline data were determined using X2 and Kruskall-Wallis tests
  • Non-parmetric statistical analysis was used to evaluate behavior change. The method, developed by Svensson, distinguishes systematic differences between paired assessments from the random component of variability
  • Relative operating characteristic curves (ROC) were determined by plotting cumulative relative frequencies of categories regarding fish consumption for baseline and follow-up evaluations. A systematic disagreement between values were expressed by a measure called a relative position (RP). RP values were between negative one and one. Values close to zero indicate no disagreement in baseline and follow-up values
  • The McNemar test was used to analyze differences between baseline and follow-up evaluations
  • The Mann-Whitney U test  was used to detect differences regarding change in knowledge between groups. 
Data Collection Summary:

Timing of Measurements

  • At the beginning of the study, schools were informed that a study about fish consumption in the school canteen was going to take place. Students were informed that the study would include completion of a questionnaire and observation of consumption would be performed. Students were also informed at this time that participation would be voluntary
  • No details of the home economics intervention was provided
  • Measurements were gathered before and after the interventions in all three groups
  • The study period was five weeks in length.

Dependent Variables

  • Consumption of fish meals measured through direct observation
  • Knowledge about fish measured through a questionnaire which consisted on 10 items.

Independent Variables

Lessons offered through home economics courses.

Control Variables

  • Number of times fish meals were offered during the study period (five times; once per week)
  • Age.
Description of Actual Data Sample:
  • Initial N: N=390 (207 males, 183 females)
  • Attrition (final N): N=228
  • Age: Approximately 14 years of age
  • Location: Goteborg, Sweden.
Summary of Results:

Comparison of Baseline and Follow-up Knowledge in Intervention and Control Groups Measured in Percent Correct Responses to Survey Questions

Survey Question Control N=83 School Lunch Intervention N=58 School Lunch + Home Ec. Intervention N=87
 

Baseline

Follow-up

Baseline

Follow-up

Baseline

Follow-up

The fat in fish is good for the heart.

36

44

30

48 (P<0.05)

48

69 (P<0.01)

Fatty fish is, for example, salmon and mackerel.

28

43

34

58

47

64 (P<0.01)

Saturated fat is healthier than unsaturated fat.

11

10

4

25 (P<0.01)

4

27 (P<0.001)

Total number of correct responses

3.2

3.4

2.8

4.1 (P<0.001)

3.8

4.8 (P.<0.001)

 

Systematic Disagreement in Relative Position Between Baseline and Follow-up Evaluation for Fish Consumption and By Gender

    Control School Lunch Intervention School Lunch + Home Ec. Intervention
Total Group
N
RP; CI=95%
83
-0.08 (-0.17 to 0.01)
58
0.10 (-0.02 to 0.22)
87
0.15 (0.06 to 0.24)
Boys
N
RP; CI=95%
41
-0.09 (-0.22 to 0.03)
20
0.05 (-0.17 to 0.27)
48
0.17 (-0.35 to 0.69)
Girls
N
RP; CI=95%
42
-0.07 (-0.20 to 0.05)
38
0.12 (-0.03 to 0.28)
87
0.12 (-0.03 to 0.27)

Additional Findings

  • Gender differences regarding baseline behavior was found to be significant (P<0.01). A higher percentage of boys were fish eaters at baseline than girls
  • Students enrolled in the SL + HE intervention were engaged in cooking classes, which may have led to increased dietary acceptance of fish
  • Observer bias was not noted since consumption of fish decreased during the study period for the control group.
Author Conclusion:
  • It is possible to influence adolescence consumption of fish through modifications in meals and education
  • The school canteen and home economics courses can serve as a means of promoting healthy diets in adolescents.
Reviewer Comments:

School recruitment methods were not described. The following limitations were noted:

  • Baseline differences between groups might have influenced the results (some pupils were fish eaters and some were not)
  • More boys ate fish than girls at baseline
  • Factorial design was not used
  • The impact of home economics courses alone was not viewed.

Research Design and Implementation 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 nutrition or dietetics practice?
Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies)
Yes
 
Validity Questions
1. Was the research question clearly stated?
N/A
  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?
No
3. Were study groups comparable?
No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)
???
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?
No
  3.3. Were concurrent controls used? (Concurrent preferred over historical controls.)
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 or cross-sectional 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. Criterion may not be applicable in some cross-sectional studies.)
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?
???
  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?
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?
No
  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?
N/A
  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?
No
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