HD: Food Security (2011)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

The purpose of this study was to determine the relationships between Food Stamp Program Participation, household food insecurity and select dimensions of children's academic, social and physical development over four years. Specifically, the researchers were investigating whether changes in Food Stamp Program participation were associated with changes in children's reading and mathematics performance, social skills development and weight gain, while controlling for changes in food insecurity and other covariates and whether Food Stamp Program participation mollified the relationships between need for food assistance and these outcomes.

Inclusion Criteria:
  • Data were obtained from the Early Childhood Longitudinal Study, Kindergarten cohort, a nationally-representative cluster sample of 21,260 kindergarten children attending 1,592 elementary schools in 1998 to 1999
  • Children with full data available at both kindergarten and third grade were used in this study.
Exclusion Criteria:

Children with incomplete data at kindergarten or third grade were not included.

Description of Study Protocol:

Recruitment

Data were obtained from children participating in the Early Childhood Longitudinal Study, Kindergarten cohort, who had full data available at both kindergarten and third grade. 

Design

  • Data were obtained when the children were in kindergarten and third grade
  • Parents were asked whether anyone in the household had received food stamps in the past 12 months
  • Household food insecurity was measured using the USDA's Household Food Security Module; this module was administered to parents by written survey in the spring of 1999 and the spring of 2002
  • Households that affirmed one or more items were classified as food-insecure
  • Mathematics and reading performance were assessed in kindergarten and third grade
  • Children's heights and weights were directly assessed at both kindergarten and third grade. Each was measured twice to minimize measurement error and the mean of each set of values was used.
  • Children's social skills were assessed by teacher questionnaires. 
Statistical Analysis
  • For changes in weight and height, initial mathematics score and initial reading score, logarithmic transformations were used
  • Multiple linear regression was used to test for differential effects in changes for the four child development outcomes of interest (mathematics score, reading score, weight and social skills score)
  • The SAS Surveyreg procedure was used to account for effects of survey clustering, primary sampling units and sample weights
  • Each outcome was analyzed using a fixed-effects model
  • The difference model was used to remove individual fixed effects and eliminate the influence of time-invariant observed and unobserved heterogeneity, by differencing-out effects of factors that remain unchanged over time and focus on transitions.
Data Collection Summary:

Timing of Measurements

Data were collected when children were in kindergarten and third grade.

Dependent Variables

  • Changes in reading performance
  • Changes in mathematics performance
  • Social skills development
  • Weight gain.

Independent Variables

Participation in the Food Stamp Program.

Description of Actual Data Sample:
  • Initial N: Approximately 10,600 children
  • Attrition (final N): Reading score, 4,292 males and 4,175 females; mathematics score, 4,450 males and 4,321 females; weight change, 4,305 males and 4,164 females; social skills, 3,644 males and 3,628 females
  • Age: Not specified, however all children involved were in kindergarten through third grade
  • Ethnicity: Not specified
  • Other relevant demographics: Not specified
  • Anthropometrics: Not specified
  • Location: United States; exact locations involved were not specified. 

 

Summary of Results:

Key Findings

  • From Kindergarten to Third Grade, children in households that started Food Stamp Program participation had a three-point greater change in both reading and mathematics score than did children in households that stopped Food Stamp Program participation
  • This association was significant only for female students
  • There were no differences in change in weight or social skills score with a change in Food Stamp Program participation.

Variables

Effect of Starting Food Stamp Program Participation (Compared with Stopping Participation)

Statistical Significance of Group Difference

Change in Reading Score

All

2.994 (N=8467)

P<0.072

Males
0.132 (N=4292)
P<0.967
Females
5.869 (N=4175)
P<0.002
Change in Mathematics Score All
2.851 (N=8771)
P<0.036
Males
1.941 (N=4450)
P<0.328

Females

3.426 (N=4321)

P<0.031

 

Author Conclusion:
  • With other factors controlled, starting Food Stamp Program participation during the four years from Kindergarten to Third Grade was associated with about a three-point greater improvement in reading and mathematics score, as compared with stopping Food Stamp Program participation during that period. However, it was for female students only that this association was large and significant.
  • In addition, children in households starting Food Stamp Program participation had slightly (but not significantly) less weight gain, compared with children in households stopping Food Stamp Program participation
  • Food Stamp Program participation may act as a financial or social resource to counter the effects of stress resulting from food insecurity or other material hardships
  • Food Stamp Program participation, plausibly, has beneficial effects for children on non-nutritional outcomes, specifically academic learning during the first four years of school. The mechanisms for this relationship are not well elucidated and may be through both dietary intake and stress.
  • The Food Stamp Program should be understood as a means of enhancing academic performance and learning among school children, as well as enhancing food expenditures and access. 
Funding Source:
Government: UDSA Economic Research Service
Reviewer Comments:

The authors did not discuss limitations to this study, nor did they provide information on the locations of the children participating, the ethnic background and SES of the children, when exactly data was collected and who collected the data.

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) N/A
  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) N/A
 
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? ???
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? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? No
  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? 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.) N/A
  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? 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? 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)? 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? No
  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