EAL

AWM: Nutrition Education (2006)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine whether the relationship between income and dietary quality is modified by food label use.

Inclusion Criteria:

20 - 60 year old respondents who were either household meal preparers, meal planners or food shoppers. Sample consisted of noninstitutionalized persons living in households in the US from 40 analytic domains defined by sex, age (10 groups), and income levels.

Exclusion Criteria:

Not mentioned.

Description of Study Protocol:

Recruitment

Using a master sample of 1990 US population estimates from March 1994 Current Population Survey, nationally representative sample was obtained for 1994-1996 CSFII/DHKS. A stratified, multistage, area probability sample design was used to draw the sample. For the DHKS, sample individuals were selected from among CSFII Day 1 intake respondents > 20 years old. Overall response rates were 76.1% for CSFII and 73.5% were DHKS.

Design

Cross-sectional Study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

Data analysis from the 1994-1996 CSFII and DHKS.

Statistical Analysis

Preliminary multivariate logistic regression analyses completed. Final descriptive statistics by food stamp status and the multivariate logistic regression models were run with WesVar software to account for design effect and adjust the standard errors of the regression parameters accordingly. The key dependent variable was the HEI, which was computed for each of the 2 CSFII intake days based on the 24-hour recall data. Multivariate logistic regression was used to test fot the food label x income category interaction of the HEI after controlling for level of education, gender and age, race, interview language, household food stamp status, nutrition knowledge and season of year in which interview conducted.

Data Collection Summary:

Timing of Measurements

Data from the 1994-1996 Continuing Survey of Food Intake by Individuals and the Diet and Health Knowledge Survey.

Dependent Variables

Healthy Eating Index: how closely individuals meet recommended intakes

Independent Variables

Demographic information
Food intake information

Control Variables

Description of Actual Data Sample:

Initial N: 2952 DHKS respondents.

Attrition (final N): 2952 respondents, ~1/3 male

Age:

Ethnicity: 80% Caucasian

Other relevant demographics: 16% of individuals were living at or below 130% of the poverty line, 10% did not complete high school

Anthropometrics (e.g., were groups same or different on important measures)

Location: Nationally representative sample

Summary of Results:

Other Findings

About 70% of respondents reported using food labels.

The influence of income on dietary quality is mediated by food label use.

Those who were wealthier and used food labels were significantly less likely to have a lower Healthy Eating Index compared with the reference group formed by those in the lower income category who did not use food labels [OR = 0.42, 95% CI: 0.31, 0.56].

By contrast, those who were wealthier but did not use food labels were as likely as the reference group to have a low HEI (OR = 1.08, 95% CI: 0.74, 1.54).

Those who were poorer but used food labels were significantly less likely to have a low HEI compared with the reference group (OR = 0.62, 95% CI: 0.48, 0.80).

Those with a higher income level were less likely than their lower income counterparts to have a lower HEI (OR: 0.42 vs 0.62, respectively).

Among higher income respondents, those who used food labels were less likely to have a low HEI compared with their counterparts who did not use the food label nutrition panel (OR: 0.42, 95% CI: 0.31, 0.56 vs OR: 1.08, 95% CI: 0.74, 1.54, respectively).

Author Conclusion:

In conclusion, food label use is associated with improved dietary quality among all income groups with a greater benefit of use among higher income individuals. Income is not associated with improved dietary quality in the absence of food label use.

Funding Source:

Government:

USDA

Reviewer Comments:

Nationally representative sample. Self-reported 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)	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?	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)	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.)	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?		N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	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?	N/A
	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?		N/A
	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?	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?	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?	N/A
	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?		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