PDM: Prediabetes (2013)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • to assess the efficacy of an intensive diet-exercise program in preventing or delaying type 2 diabetes mellitus in subjects with impaired glucose tolerance
  • to evaluate the efficacy of the intervention program on cardiovascular risk factors
  • to assess the determinants for the progression to diabetes in persons with impaired glucose tolerance.


Inclusion Criteria:

1. Diagnosis of impaired glucose intolerance based on criteria adopted by the WHO in 1985 (mean of duplicate 2-h plasma glucose 7.8-11 mmol/L with 75-g glucose load with fasting plasma glucose <7.8 mmol/L).

2. Subjects also admitted to the study based on one OGTT, or plasma glucose >=6.4 mmol/L

3. BMI >25

4. 40-64 yr of age

Exclusion Criteria:

1. previous diagnosis of diabetes mellitus except for GDM

2. involved in regular vigorous physical activity

3. treatment to lower blood glucose

4. chronic disease that would likely limit the ability to continue with the study for 6 yr.

5. thyroid or liver disease
Description of Study Protocol:

Recruitment: Each center recruited 100 subjects. The recruitment started after a pilot study in 1993 and was completed in 1998.  Subjects were recruited through screenings, epidemiological  surveys, newspapers, and relatives of known patients.

Study Design: Multicenter randomized control trial.  Designed to be large enough to detect a 35% reduction in diabetes incidence with an intensive diet and exercise interviention with 80% power.

Blinding Used (if applicable):  none

Intervention (if applicable):

Subjects randomly assigned to control group or intervention group.

Statistical Analysis:

  • two-tailed t test used to analye the differences within groups at baseline and at year 1
  • unpaired t test to analyze the difference in mean change from baseline year 1 between the intervention and control groups



Data Collection Summary:

Timing of Measurements

  • Repeat OGTT yearly or at each visit.  If the WHO criteria are met, then diabetes is confirmed with a second OGTT at least one week after the first one.
  • medical history and physical exam every year
  • height, weight, waist and hip circumferences and sagittal and transverse diameters measured annually.

Dependent Variables

  • Primary outcome:  development of type 2 diabetes mellitus
  • Secondary outcomes:
    • plasma glucose
    • serum insulin
    • HbA1c
    • blood pressure
    • serum lipids
    • uric acid
    • cardiovascular morbidity and mortality

Independent variables

  • Control group: Nutritionist advises subjects to adjust fat intake to <30% total calories and energy intake to reduce BMI <25 and encourages physical activity; additional advice at annual follow-up visits.
  • Intervention group: Nutritionist gives frequent individualized instruction and group instruction to lower saturated fat and increase fiber, study visits at 1-2 wk, 5-6 wk, 3, 4 and 6 mos and thereafter every 3 mos. 3-day food records used for initial counseling and for follow-up every 3 mos throughout the study. Individually guided to increase physical activity: endurance activities (walking, jogging, swimming, aerobic games, skiing) and 2 times/wk supervised resistance training.

Control Variables


Description of Actual Data Sample:

Initial N:  523 recruited, 212 studied at the time of this interim report.  All subjects had participated in the study for at least one year.

Attrition (Final N): unclear; no mention of withdrawals in the first year

Age:  mean 54±7 for intervention group

Ethnicity:  not specified

Other relevant demographics:  none mentioned

Anthropometrics:  BMI 31.3±5 in intervention group

 Location:  Finland

Summary of Results:

Other Findings

During the first year, weight loss in the first 212 study subjects was 4.7±5.5 vs. 0.9±4.1 kg in the intervention and control groups, respectively. (P<0.0001).

The plasma glucose concentrations (fasting: 5.9±0.7 vs. 6.4±0.8 mmol/L, P<0.001; and 2-hr: 7.8±1.8 vs. 8.5±2.3 mmol/L, P<0.05) were significantly lower in the intervention group after the first year of intervention.

The intervention subjects had 7 sessions with a nutritionist whereas the control group had 1 session with a nutritionist during the first year

Author Conclusion:

The interim results show the efficacy and feasibility of the lifestyle intervention program.

The difference in plasma glucose concentrations between the groups was striking. Even during the first year, there was some deterioration in fasting glucose concentrations in the control group. In the 2-hr plasma glucose concentration an improvement in both groups was noted but the change was significant only in the intervention group. The mean value of the 2-hr plasma glucose at 1-yr in the intervention group (7.8 mmol/L) was only minimally above normal according to WHO criteria.

We recommend that this intervention strategy be used to lower the incidence of type 2 diabetes mellitus as well as CVD.

Funding Source:
Government: Ministry of Education (Finland)
Reviewer Comments:
This type of intervention could be used to prevent recurrence of GDM and the development of type 2 diabetes mellitus in women with a history of GDM. The significance of this study, is the frequency of the encounters with the nutritionist.
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) 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? 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
4. Was method of handling withdrawals described? No
  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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  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
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? 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.) Yes
  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? 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.6. Were extra or unplanned treatments described? No
  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? No
  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)? No
  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? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. 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