PDM: Prediabetes (2013)

Citation:

Allen P, Thompson JL, Herman CJ, Qualls C, Helitzer DL, Whyte AN, Wolfe VK. Impact of periodic follow-up testing among urban American Indian women with impaired fasting glucose. Prev Chronic Dis. 2008; 5(3): A76.

PubMed ID: 18558026
 
Study Design:
Prospective Cohort Study
Class:
B - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To conduct an analysis of results among a small subset of women with IFG (impaired fasting glucose) at baseline, some of whom who participated in a lifestyle intervention study, with an 18-month follow-up.

 

Inclusion Criteria:
  • Self-identification as American Indian
  • Females aged 18 to 40 at baseline
  • Without diabetes at baseline as measured by FBG (fasting blood glucose) less than 7.0mmol per L (less than 126mg per dL)
  • Planning to stay in the local area for two years
  • Not pregnant and not planning a pregnancy in the next two years.
Exclusion Criteria:

Did not meet inclusion criteria.

Description of Study Protocol:

Recruitment

Recruited via word of mouth, flyers posted at outpatient clinics, colleges and major employers and local media.

Design

  • Cohort study, secondary analysis of a subset of RCT participants
  • Block-randomized by FBG level into two groups. Intervention was implemented between the baseline and six-month clinic measures, with follow-up clinic measurements at 12 and 18 months. 

Intervention

Discussion-format group sessions once a month including:

  • Written and oral didactic material with culturally appropriate graphics
  • Participation in small-group discussions.

Statistical Analysis

Differences from baseline were analyzed by using one-way repeated measures analyses of variance (RM ANOVA). Post-hoc comparisons of mean changes at each time from baseline were obtained by using paired T-tests. Also, given the small sample size, pooled analyses of intervention and control group were conducted.

Data Collection Summary:

Timing of Measurements

Measurements done at baseline and six, 12 and 18 months.

Dependent Variables

  • Laboratory data: Glucose, insulin, lipids
  • Insulin sensitivity estimated using the quantitative insulin sensitivity check index: 1/(log insulin + log glucose)
  • Anthropometric data: Height, weight, waist circumference
  • Body composition measured with quantum bioelectrical impedance using a prediction equation validated with American Indian women.

Independent Variables

  • Lifestyle intervention
  • Block Food Frequency Questionnaire
  • 24-hour dietary recall
  • Physical activity assessed using the Modifiable Activity Questionnaire (this has been tested for reliability and validity among Pima Indian adults)
  • Submaximal bicycle ergometer test to predict peak oxygen consumption.
Description of Actual Data Sample:
  • Initial N: 200 eligible volunteers; 42 (21%) had IFG (impaired fasting glucose) at baseline
  • Attrition (final N): Started with 42 women; 30 women completed measurements at 18 month follow-up
  • Age: 31.6 years old
  • Ethnicity: Urban American Indian
  • Anthropometrics: Baseline BMI was 34.1 (7.0)
  • Location: New Mexico.
Summary of Results:

Key Findings 

Variables

Baseline (N=42)

Six-month Change from Baseline (N=33)

12-month Change (N=33)

18-month Change (N=30)

Overall Change over Time

P-value

Fasting blood glucose, mmol per L  5.87 (0.32)  -0.22 (0.30)*  -0.19 (0.50)*  -0.39 (0.60)*  <0.001 
Total fasting cholesterol, mmol per L  4.42 (0.81)  -0.21 (0.58)*  -0.24 (0.58)*  -0.10 (0.50)  0.03 
LDL, mmol per L  2.48 (0.62)  -0.18 (0.48)  -0.23 (0.45)*  -0.09 (0.46)  0.009 
Total energy intake, kcal per day  2,307.1(971.6)  -349.2 (958.4)  -550.5 (683.2)*  -565.5 (853.6)*  <0.001 
Total fat intake, g per day  100.0 (45.6)  -20.5 (46.6)*  -20.4 (22.6)*  -24.2 (48.3)*  0.004 
Saturated fat intake, g per day  31.1 (15.1)  -6.2 (16.1)  -6.1(6.8)*  -7.7 (16.0)* 0.006
Total sugar intake, g per day  111.2 (66.8)  -37.3 (78.3)*  -29.2 (77.9)*  -24.2 (81.7)  0.03 
Intake of sweetened beverages, oz per day  24.3 (20.0)  -11.32 (20.8)*  -7.17 (20.1)*  -5.12 (30.3)  0.02 
Television watching, hours per day  2.3 (2.1)  -0.6 (2.1)  -0.9 (1.9)*  -0.6 (2.0)  0.03 

* Significant difference from baseline value per paired T-test, P<0.05.

Other Findings

  • Of the women who completed follow-up, 62% converted to normal FBG by 18 months
  • Other improved metabolic values included significant decreases in mean fasting total blood cholesterol and LDL-cholesterol levels
  • The women reported significant overall mean decreases in intake of total energy, saturated fat, total fat, total sugar, sweetened beverages, proportion of sweet foods in the diet, and hours of television watching. 
Author Conclusion:

Women with IFG (impaired fasting glucose) in this study benefited from learning their FBG values and reporting their dietary patterns; they made dietary changes and improved their FBG and lipid profiles. These results support periodic dietary and body composition assessment as well as glucose monitoring among women with IFG.

Funding Source:
Government: National Institute of Diabetes and Digestive and Kidney Diseases, National Intstitutes of Heath; and DHHS/NIH/NCRR-GCRC
Reviewer Comments:
  • This was part of a larger study so a lot of data was not shown. Did state in limitations that statistical power was not great enough to detect differences in mean changes between the intervention and control groups because of the small sample size and wide variability in the women's dietary and metabolic values.
  • Small number of women in this subset/intervention group; the study started with 42 and the final number was 30
  • Of the 42 women, 19 were in the intervention group and 23 in the control group. Due to the small sample size the analyses were pooled and disregarded intervention group status (so cannot state effect the intervention itself had on changes)
  • Discussed these limitations well.
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? ???
2. Was the selection of study subjects/patients free from bias? ???
  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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? 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? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
  3. Were study groups comparable? ???
3. Were study groups comparable? ???
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) 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? ???
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? ???
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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? ???
  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? ???
  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
  3.5. 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
  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? ???
4. Was method of handling withdrawals described? ???
  4.1. Were follow-up methods described and the same for all groups? 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%.) 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%.) No
  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? ???
  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
  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? Yes
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  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.) Yes
  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.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  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? ???
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? ???
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? 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
  6.2. 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
  6.3. 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? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? ???
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? ???
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? ???
  6.6. Were extra or unplanned treatments 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
  6.7. 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? 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  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)? N/A
  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)? ???
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? ???
  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? N/A
  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. 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? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes