Health Disparities

HD: Effectiveness of Nutrition Intervention Methods (2010)


Brown SA, Blozis SA, Kouzekanani K, Garcia AA, Winchell M, Hanis CL. Dosage effects of diabetes self-management education for Mexican Americans: The Starr County Border Health Initiative. Diabetes Care. 2005 Mar; 28 (3): 527-532.

PubMed ID: 15735182
Study Design:
Group Randomized Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To compare two culturally-competent, diabetes self-management interventions designed for Mexican Americans: "Extended" and "compressed" interventions.

Inclusion Criteria:
  • Between 35 to 70 years of age
  • Diagnosed with type II diabetes
  • Two verifiable FBG ≥140mg/dL or taking or have taken insulin or hypoglycemic agents for  up to one year
  • Provided written informed consent.


Exclusion Criteria:
  • Individuals who were pregnant or had medical conditions for which changes in diet and walking were contraindicated
  • Less than 35 years old or more than 70 years old.
Description of Study Protocol:


Subjects were selected from rosters of ongoing genetic studies. 114 individuals were allocated to the "compressed" group and 102 to the "extended" group. Four groups of eight subjects and their support people made up each cohort; two groups were randomly assigned to the "compressed" intervention and two to the "extended." The same process occurred every three months until 23 groups were enrolled.


Group Randomized Trial


The initial "extended" intervention was an intensive one-year, series of 12 weekly two-hour sessions on nutrition, home glucose monitoring, physical activity and other self-management topics, followed by 14 two-hour support group sessions to promote behavioral change through problem solving and goal setting. The "compressed" intervention involved eight weekly two-hour educational sessions followed by support sessions strategically held at three, six and 12 months. Both interventions covered similar information.

Statistical Analysis

The interventions were compared with a prospective, quasi-experimental, repeated measures, nested design. To handle missing data in the longitudinal analyses, hierarchical linear models were applied by which non-randomly missing data were handled by including indicators of missing-data patterns. All analyses tested the main effects for age, intervention, gender, number of hours of intervention attendance and all two-way interactions. To better understand "dosage effects", a series of two ANCOVA were conducted. Baseline measures were treated as covariates and three-month measures were treated as covariates for the 12-month analyses.

Data Collection Summary:

Timing of Measurements

Intervention groups' baseline data was collected and then started the program immediately with study data collection as cohorts reached three, six, 12, 24 and 36 month examination dates.  The "compressed" intervention involved eight weekly two-hour educational sessions followed by support sessions strategically held at three, six and 12 months. Measures of intervention effectiveness were demographics (age, gender, age of diabetes diagnosis, etc.); acculturation, family, medical and medication history; diabetes knowledge, health beliefs, HgbA1c, FBG, blood pressure, BMI, cholesterol and triglycerides. FBG was performed in the research field office with a desktop glucose analyzer. HgbA1c was analyzed at the University of Texas-Houston.  The Spanish language knowledge instrument was based on national standards and written to facilitate reading aloud to subjects.

Dependent Variables

  • HgbA1c
  • FBG
  • Knowledge.

Independent Variables

"Extended" or "compressed" culturally-competent programs offering educational and support groups sessions.

Control Variables

To control for between group differences in socioeconomic status and foster group support between weekly sessions, each group was organized within a specific area of the county and then randomly assigned to either "compressed" or "extended" conditions.

Description of Actual Data Sample:
  • Initial N: 216 (114 "compressed", 102 "extended")
  • Attrition (final N): 206
  • Age: 35 to 70 years
  • Ethnicity: Mexican-American
  • Other relevant demographics: Low socioeconomic status
  • Location: Starr County, Texas. 
Summary of Results:

 Key Findings

  • The interventions were not statistically different in reducing HgbA1c, however both were effective
  • A "dosage effect" of attendance was found with the largest reductions in HgbA1c achieved by those who attended more of the "extended" intervention
  • Attendance at both educational and support sessions was related to greater knowledge levels at 12 months
  • At 12 months, knowledge was in general positively related to the number of hours of attendance (B=0.08, T=5.26, P<0.001).
Author Conclusion:

The purpose of this study was to modify an original intensive year-long program into a shorter, more resource-efficient strategy that would be more easily integrated into clinical settings. The effectiveness of culturally-competent diabetes self-management education was demonstrated. 

Data from this study indicate a decrease in HgbA1c in both the "extended' and "compressed" interventions, but the best result occurred in the "extended" intervention for individuals who received the maximum dose (attended ≥50% of the intervention sessions). 

Diabetes self-management programs should be prescribed in a manner similar to diabetes medications. For individuals with few resources from poor backgrounds, similar to Starr County participants, the "extended" program of 52 hours over 12 months is recommended. 

Interventions designed to maintain long-term benefits of self-management programs must be tested to determine the most cost-effective strategies.

Funding Source:
Government: NIDDK/NIH, grant no. DK48160
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) Yes
  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.) 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? 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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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.) ???
  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? N/A
  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? 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
  6.8. 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? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes