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HD: Effectiveness of Nutrition Intervention Methods (2010)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • To determine whether the Mississippi peer counseling program has effectively increased the incident of breastfeeding
  • To indentify staff or program characteristics that are associated with higher success rates.
Inclusion Criteria:
  • Infants enrolled in WIC clinics in Mississippi
  • Had a first clinic visit between 1989 and 1993
  • Clinic must have had a peer counseling program as of January 1, 1993 for inclusion in secondary research question.

 

Exclusion Criteria:

None listed.

Description of Study Protocol:

Recruitment

All children enrolled in WIC programs in Mississippi from 1989 to 1993.

Design

  • Before-after study
  • Pediatric Nutrition Surveillance System (PedNSS) used for data from 1989 to 1993:
    • Continuous statewide surveillance system 
    • Data collected each time a child visits a WIC clinic
    • Only data for 'infant's first visit' used in analysis
  • Change in proportion of infants 'ever breast-fed' from 1989 to 1993 compared in clinics with and without peer counseling program
  • Peer counseling program questionnaire mailed in 1994 to all clinics with programs at that time
  • Change in proportion of infants 'ever breast-fed' from 1989 to 1993 in clinics with peer counseling programs with and without specific staff and program characteristics.

Intervention

  • Peer counseling program implemented in WIC clinics in the state of Mississippi
  • Established in October 1990 and programs were added in counties over time
  • A peer counselor is assigned a WIC client and makes contact immediately after enrollment and must continue contacts at least once a month throughout pregnancy and after baby is born:
    • Peer counselor may be a lactation consultant, lactation specialist or a peer counselor
    • Contacts may be via telephone, mailings or prenatal classes
    • Discussion includes breastfeeding advantages and how to start as well as post-partum issues.

Statistical Analysis

  • Baseline proportion of 'ever breastfed' determined in 1989
  • 1993 used as comparative year after programs in WIC clinics were begun
  • Absolute differences in proportion of infants 'ever breast-fed' in clinics from 1989 to 1993 with and without peer counseling programs were measured and a T-test was used for level of significance:
    • E= (Pa,1993- Pa,1989) - (Pb,1993- Pb,1989)
    • Pa = Clinics with peer counseling
    • Pb= Clinics without peer counseling
  • Logistic regression used to test significance of the ratio of the odds ratios for trend:
    • R = ORa/ORb
    • ORa = Odds ratio of ever breastfeeding in 1993 vs. 1989 in clinics with peer counseling
    • ORb = Odds ratio of ever breastfeeding in 1993 vs. 1989 in clinics without peer counseling
  • Analogous statistics used for the program and staff characteristics comparing clinics with peer counseling programs with and without certain characteristics:
    • E= (Pa,1993- Pa,1989) - (Pb,1993- Pb,1989)
    • Pa = Clinics with characteristic
    • Pb = Clinics without characteristic
    • R = ORa/ORb
    • ORa = Odds ratio of ever breastfeeding in 1993 vs. 1989 in clinics with characteristic
    • ORb = Odds ratio of ever breastfeeding in 1993 vs. 1989 in clinics without characteristic.
Data Collection Summary:

 

Timing of Measurements

  • Data extracted from PedNSS:
    • 1989 and 1993
    • Infants first visit used
  • Questionnaire mailed in 1994 to all WIC clinics with a peer counseling program as of January 1, 1993.

Dependent Variables

Incidence of breastfeeding was calculated as proportion of infants ever breastfed at a first visit to a WIC clinic in 1989 and 1993.

Independent Variables

  • Presence of a peer counseling program at WIC clinic
  • Staff characteristics:
    • Job title
    • WIC experience
    • Race
    • Age
    • Professional experience
    • Breastfeeding history
  • Program characteristics
    • Length of time program in place
    • Average monthly caseload
    • Frequency of contact during pregnancy
    • Amount of time peer counselors spent each month with client
    • Amount of time lactation specialists and consultants spent with each client
    • Total hours worked divided by the number of woment enrolled
    • Lifestyle discussion.

Control Variables

Race.

 

Description of Actual Data Sample:

Initial N

  • 30,000 children per year included in data set
  • 140 WIC clinics had peer counseling programs in their county as of January 1, 1993
  • 97 staff members from 51 clinics were mailed questionnaires.

Attrition (Final N)

  • 18,889 infants in 1989 (63%)
  • 17,216 infants in 1993 (57%)
  • 36% (51 of 140) WIC clinics had peer counseling programs by January 1, 1993
  • 94% (91/97) of staff members returned questionnaires. 

Age

  • Infant, first visit to WIC clinic 
  • Exact age not given.

Ethnicity and Demographics

  • WIC enrollees from 1989 to 1993: 
    • Median age of mothers enrolled in WIC was 23 years
    • 38% infants classified as white non-Hispanic
    • 61% infants classified as black
  • Staff and program characteristics
    • Approximately half of staff classified as peer counselors
    • Approximately half of staff had previously been WIC participants
    • Median age of staff was 32 years
    • 86% of staff were white non-Hispanic
    • All staff members had children and had breastfed their last child
    • Median duration of breastfeeding among staff was 18 months
    • Staff worked 10 hours per week and contacted 40 to 49 WIC participants each month
    • Median of seven contacts during pregnancy for peer counselors
    • Median of three contacts for lactation specialists and consultants.

Anthropometrics

Baseline incidence of breastfeeding was higher in counties that implemented peer counseling program than those who did not (9.2% vs. 12.3%).

 Location

WIC clinics in Mississippi.

 

Summary of Results:

 

Program Effectiveness

Overall Percentage of WIC Infants in Mississippi Who Were Ever Breastfed Rose from 10.9% in 1989 to 15.8% in 1993 

 

Without Program

With Program

 Difference (E)

Ratio of Odds ratio for trends (R)

All WIC enrollees

  

 

  

 

1989

9.2

12.3

    

1993

 10.7 19.9 6.1* 1.48*

White

 

 

  

 

1989

 19.6 20.9    

1993

 22.0 30.8 7.5* 1.46

Black

 

 

  

 

1989

 3.7 6.3    

1993

 5.1 12.1 4.4* 1.47
         
        Adjusted for all other characteristics and race
One or more specialist or consultant in clinic     4.4* 1.47*
One or more peer counselor in clinic     -2.6 0.72*
 50% or more of staff was in WIC     0.5 1.26*
Mean age of staff more than 35 years     3.2* 1.29*
Program started before July 1991     2.1* 1.25*
PCs spent more than 45 minutes per participant     2.9* 1.50*

 * Significant at the 5% level.

Author Conclusion:
  • The incidence of breastfeeding rose more significantly in clinics with peer counseling programs than in those without programs
  • Demonstrates ability of program to affect overall incidence of breastfeeding on a population basis, especially in low-income populations
  • Certain program and staff characteristics can be attributed to the success of the peer counseling program by affecting breastfeeding rates.
Funding Source:
Government: Centers for Disease Control, Mississippi WIC program
Reviewer Comments:
  • Authors use proportion of infants ever breastfed as a surrogate for incidence rates of breastfeeding in this population
  • Unclear as to actual effect on incidence state-wide, may be only applicable to a small sample of low-income infants in Mississippi enrolled in WIC
  • Small sample size of clinics in state, only 51 studied
  • Large amount of missing data, up to 40% in 1993, may affect validity of results.
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
  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
  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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? No
2. Was the selection of study subjects/patients free from bias? No
  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? No
  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? No
  2.2. Were criteria applied equally to all study groups? ???
  2.2. Were criteria applied equally to all study groups? ???
  2.3. Were health, demographics, and other characteristics of subjects described? No
  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? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
  3. Were study groups comparable? 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) No
  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? No
  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 or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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
  3.4. 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.) No
  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.) No
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? 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. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? No
  4.1. Were follow-up methods described and the same for all groups? No
  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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? 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
  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. 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
  5.1. 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.) 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
  5.3. 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
  5.4. 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
  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. 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
  6.1. 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
  6.2. 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
  6.3. 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
  6.4. 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? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  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
  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. 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
  7.1. 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
  7.2. 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
  7.3. 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? No
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? No
  7.5. Was the measurement of effect at an appropriate level of precision? 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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)? No
  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)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  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
  8.6. 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
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? No
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes