PDM: Prediabetes (2013)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • To determine the feasibility and effects of a lifestyle intervention program designed to prevent or delay the onset of type 2 diabetes mellitus in subjects with impaired glucose tolerance (IGT).
Inclusion Criteria:
  • Body Mass Index (BMI) >25 kg/m2
  • IGT
  • Age 40-65 years
Exclusion Criteria:
  • Not discussed
Description of Study Protocol:


  • Advertisements in local newspapers
  • Recruited from previous epidemiologic surveys
  • Population screenings


  •  Randomized Controlled Trial

Blinding used (if applicable)

  •  Not applicable

Intervention (if applicable)

  • Subjects in the control group were given general verbal and written diet and exercise information at baseline and at annual visits.  No specific individual instruction was given.
  • Subjects in the intervention group were given detailed advice to achieve goals of weight reduction of 5% or more, total fat intake of less than 30% of energy consumed, saturated fat intake less than 10% energy consumed, fiber intake of 15 grams per 1000 kcalories and moderate exercise of 30 minutes per day or more.  Subjects had 7 sessions with a nutritionist the first year and every 3 months thereafter.  Exercise sessions were offered.

Statistical Analysis

  • Survival curves were calculated to estimate the cumulative incidence of diabetes.  The difference in incidence of diabetes in the two groups was tested using the two-sided log-rank test.
  • All analyses of endpoints were based on the intention-to-treat principle.


Data Collection Summary:

Timing of Measurements

  •  Fasting glucose

Dependent Variables

  • Diagnosis of diabetes (fasting plasma glucose or 2-hour post-challenge plasma glucose)
  • Metabolic measures (including serum cholesterol)

Independent Variables

  •  Lifestyle changes/ study group

Control Variables

  •   None discussed
Description of Actual Data Sample:

Initial N: 522 were randomized (350 were women)

Attrition (final N):  Data analyzed intent-to-treat

Age: 55 ± 7 years

Ethnicity: Finnish

Other relevant demographics: ~ 2/3 of subjects were women

Anthropometrics:  Baseline characteristics of two groups were similar.

Location: Finland


Summary of Results:


Change in measures from baseline to 1 year


Intervention Group


Control group


Statistical Significance of Group Difference

Weight (kg)

-4.2 ± 5.1

-0.8 ± 3.7


Fasting plasma glucose (mg/dl) -4 ± 12 1 ± 12 0.0000
2-hour plasma glucose (mg/dl) -15 ± 34 -5 ± 40 0.0026
Total serum cholesterol (mg/dl) -5 ± 28 -4 ± 28 0.6232
Serum triglycerides (mg/dl) -18 ± 51 -1 ± 60 0.0010

Change in measures from baseline to 2 years


Intervention Group


Control group


Statistical Significance of Group Difference

Weight (kg) -3.5 ± 5.5 -0.8 ± 4.4 0.0001
Fasting plasma glucose (mg/dl) -2 ± 13 4 ± 14 0.0001
2-hour plasma glucose (mg/dl) -14 ± 38 0 ± 45 0.0002
Total serum cholesterol (mg/dl) -4 ± 31 0 ± 27 0.1834
Serum triglycerides (mg/dl) -18± 53 0 ± 75 0.0026

Other Findings

  • Eighty-six cases of diabetes were diagnosed by the end of the 6 year follow-up; 27 in the intervention group and 59 in the control group.
  • The difference in rates of diagnosis of diabetes between study groups was significantly different after two years.
  • The study was ended early following interim analysis of data.
  • Success in achieving food and exercise goals was measured following 1 year of intervention.  There was a strong and inverse relationship between achieving goals and diagnosis of diabetes.
Author Conclusion:
The Diabetes Prevention Study has provided unequivocal evidence that type 2 diabetes mellitus can be prevented by lifestyle interevention in middle-aged high-risk men and women.
Funding Source:
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? 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? ???
  4.1. Were follow-up methods described and the same for all groups? ???
  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? ???
  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.) ???
  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? 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? ???
  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)? ???
  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? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? No
  9.1. Is there a discussion of findings? No
  9.2. Are biases and study limitations identified and discussed? No
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