HD: Food Security (2011)

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

To examine associations between WIC participation and indicators of underweight, overweight, length, caregiver-perceived health and household food security among infants up to 12 months of age, at six urban hospitals and clinics.

Inclusion Criteria:
  • WIC-eligible caregivers of infants 12 months of age or younger
  • English or Spanish speakers (Somali included in Minneapolis)
  • Knowledgeable of the child's household
  • Willing to consent to participate in the study.
Exclusion Criteria:
  • Caregivers of children over 12 months of age
  • Accompanying a critically-ill child
  • Unable to communicate in English or Spanish (or Somali in Minneapolis)
  • Families that received private insurance
  • Caregivers who had been interviewed in the previous six months
  • Unable to provide information about WIC participation
  • Refusal of consent for any reason.
Description of Study Protocol:
  • Recruitment: Caregivers of infants were interviewed at urban medical centers in five states and Washington, D.C., from August 1998 through December 2001
  • Design: A multi-site cross-sectional study
  • Statistical analysis: Multivariate regression models were used to examine differences in weight-for-age and length-for-age Z-scores; multivariate logistic regression models were specified to model differences in the odds of overweight, caregiver reports of children's health and food insecurity among families of infants on the basis of their WIC status.
Data Collection Summary:

Timing of Measurements

  • Surveys were administered from August 1998 through December 2001
  • Survey instruments included questions regarding household characteristics, food security, federal assistance program (including WIC) participation, changes in benefit levels, child's history of hospitalization and child's health status
  • The USDA Food Security Scale was used to categorize each child's household as food-secure or food-insecure.

Dependent Variables

  • Weight-for-age
  • Length-for-age
  • Overweight
  • Caregiver's perception of child's health status
  • Household food security.

Independent Variables

WIC participation.

Control Variables

  • Study site
  • Infant's race or ethnicity
  • Infant's birth weight
  • Number of months infant was breastfed
  • Infant's age
  • Housing subsidy
  • Caregiver's employment status
  • Caregiver's education
  • Whether the household received other federal assistance.
Description of Actual Data Sample:

Initial N

11,567.

Attrition (Final N)

5,923.

Mean Age

  • No WIC (access problems): 25.8±6.9
  • No WIC (no perceived need): 27.7±7.3
  • WIC: 25.6±7.0.

Ethnicity

  • No WIC (access problems)
    • African-American: 51%
    • Hispanic: 35%
    • White: 10%.
  • No WIC (no perceived need)
    • African-American: 40%
    • Hispanic: 28%
    • White: 21%.
  • WIC
    • African-American: 52%
    • Hispanic: 39%
    • White: 7%.

Other Relevant Demographics

Married

  • No WIC (access problems): 49%
  • No WIC (no perceived need): 62%
  • WIC: 45%.

Location

  • Los Angeles, CA
  • Baltimore, MD
  • Boston, MA
  • Washington, D.C.
  • Little Rock, AR
  • Minneapolis, MN.
Summary of Results:

Unadjusted Child Health Outcomes According to WIC Participation

Outcomes Variables

No WIC (Access Problems)
N=340

No WIC (No Perceived Need)
N=188

WIC
N=5,395

Weight-for-age Z-score

-0.36± 1.28

0.10± 1.37

0.002± 1.29

  95% CI
-0.50, -0.22
-0.08, 0.29
-0.03, 0.04
P-Value
<0.0001
0.29
<0.0001
Length-for-age Z-score
-0.41 ± 0.09
0.30± 1.24
-0.006± 0.02
  95% CI
-0.57, -0.26
-0.09, 0.51
-0.05, 0.03

P-Value

<0.0001

=0.005

<0.0001

Overweight (Weight-for-Length ≥95th Percentile)

 8%

 7%

 9%

  Odds Ratio
0.84
0.79
1.00
Caregiver Perception of Infant Health (Fair or Poor)
16%
10%
11%
 

Odds Ratio

1.48

0.89

1.00

Household food security (Insecure)

28%

11%

23%

  Odds Ratio
1.29
0.40
1.00
P-Value
0.05
0.0002
 

CI: Confidence interval
OR: Odds ratio.

Author Conclusion:
  • The results provide evidence that WIC participation is associated with positive infant growth and health
    • Infants who did not receive WIC services because of access problems were more likely to be underweight, short and perceived by their caregivers to be in fair or poor health, compared with WIC assistance recipients
    • One possibility for the positive association between WIC participation and infants' growth and perceived health is that the infants receive direct benefits from the food supplements and nutritional recommendations that their families received
    • Selection bias is a serious risk. In order to reduce selection bias, we separated those who did not receive WIC assistance into caregivers who reported access problems and caregivers who did not perceive a need for WIC services.
    • It is extremely difficult to evaluate publicly funded programs like WIC. Investigators must rely on observational or quasi-experimental designs rather than experimental designs.
  • When participants are compared with eligible non-participants, selection bias is a serious risk. This investigation avoids some of the biases inherent in observational research by recruiting samples from six urban centers across the country and controlling for potentially confounding variables at the level of the community, the family and the infant.
  • Caution is warranted in interpreting the findings related to overweight
  • Weight-for-length of at least the 95th percentile among infants is not necessarily a risk factor for overweight during childhood or adulthood. Longer-term studies on children's rates of growth are necessary to determine whether WIC participation is associated with excessive weight gain.

 

Funding Source:
Not-for-profit
MAZON: A Jewish Response to Hunger, Gold Foundation, Minneapolis Foundation, Project Bread: The Walk for Hunger, Sandpiper Foundation, Anthony Spinazzola Foundation, Daniel Pitino Foundation, Candle Foundation, Wilson Foundation, Abell Foundation, Claneil Foundation, Beatrice Fox Auerbach Fund
Foundation associated with industry:
Other non-profit:
Other: W.K. Kellogg Foundation, anonymous donors
Reviewer Comments:
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? ???
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) No
  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? 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? 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? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  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)? Yes
  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? N/A
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes