MNT: Cost Effectiveness, Cost-benefit, or Economic Savings of MNT (2009)


Diabetes Prevention Program (DPP) Research Group. Within-trial cost-effectiveness of lifestyle intervention or metformin for the primary prevention of type 2 diabetes. Diabetes Care 2003; 26: 2,518-2,223.

PubMed ID: 12941712
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To assess cost-effectiveness of lifestyle and metformin interventions relative to placebo intervention.

Inclusion Criteria:
  • Patients with impaired glucose tolerance (IGT), ≥25 years of age; BMI ≥24kg/m2 
  • All direct medical and non-medical costs; indirect costs.
Exclusion Criteria:

In cost analysis, excluded costs of research component of the DPP (recruitment, data collection, surveillance). 

Description of Study Protocol:


Recruitment methods not reported in this article. From original article, recruitment was designed to enroll approximately half the participants from racial or ethnic minority groups. A four-step screening and recruitment process was developed to identify eligible participants. 


Randomized Controlled Trial; randomization/assignment to treatment groups not described.


  • Lifestyle: Achieve and maintain weight reduction of ≥7% initial body weight via diet, physical activity; 16-lessons and individual sessions (monthly); group sessions
  • Metformin vs. placebo: 850 milligram per day; at one month, 850mg twice daily; quarterly visits with case managers; standard recommendations (written materials), annual 20-30 minute individual sessions to discuss lifestyle.

Statistical Analysis

  • Based on design, cost, clinical effectiveness of interventions
  • Cost-effectiveness by age; by the impact plausible changes in both costs and outcomes
  • Cost-effectiveness of interventions as implemented in routine clinical practice.


Data Collection Summary:

Timing of Measurements

Analysis completed over three-year period.

Dependent Variables

  • Costs
  • Health utilities
  • Cost/case prevented
  • Cost/QALY gained.

Independent Variables

Lifestyle modification, metformin, or placebo.

Control Variables

  • Timing of intervention
  • IGT
  • BMI.
Description of Actual Data Sample:

Initial N

3,234 (68% Female)

Attrition (final N)

As above


Mean 51 years


45% of sample represented minority groups

Other relevant demographics

Mean BMI 34.0kg/m2


Baseline characteristics including all measured risk factors for diabetes were similar among the three study groups


DPP Coordinating Center, Rockville, Maryland


Summary of Results:


Variables Lifestyle Metformin Placebo

Direct medical ($)

Case finding


Care outside DPP













Total $ health system 7,408 7,420 5,229
Direct non-medical ($) 17,137 15,683 15,692
Indirect ($) 2,430 2,834 2,604
Total ($) society 27,065 25,937 23,525

Other Findings

  • The lifestyle and metformin interventions required more resources than the placebo intervention from a health system perspective, and over three years they cost approximately $2,250 more per participant
  • Societal perspective costs tended to be higher than from health system perspective
  • As implemented by DPP: Lifestyle and metformin cost $24,400 and $34,500 (respectively) per case of diabetes delayed or prevented. Lifestyle and metformin cost $51,600 and $99,200 (respectively) per QALY gained.  
  • As may be implemented in routine clinical practice: Lifestyle and metformin cost $13,200 and $14,300 (respectively) per case of diabetes delayed or prevented. Lifestyle and metformin cost $27,100 and $35,000 (respectively) per QALY gained.  


Author Conclusion:

Over three years, lifestyle and metformin interventions were effective treatments of diabetes and were cost-effective relevant to health system and society. Both interventions are likely to be affordable in routine clinical practice, especially if implemented in group format and with generic medication pricing.

Funding Source:
Government: NIH, NIDDK, NICHD, Office of Women’s Health, NIA, Indian Health Service, NCMHD, Office of Research on Women's Health, Indian Health Service CDC, General Clinical Research Center Program, National Center for Research Resources
Bristol-Myers Squibb, Parke-Davis
Pharmaceutical/Dietary Supplement Company:
Foundation associated with industry:
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) No
  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? ???
  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? 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? ???
  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.) N/A
  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? 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
  6.8. 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? N/A
  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)? N/A
  8.6. Was clinical significance as well as statistical significance reported? No
  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