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


Herman WH, Brandle M, Zhang P, Williamson DF, Matulik MJ, Ratner RE, Lachin JM, Engelgau MM, Diabetes Prevention Program Research Group. Costs associated with the primary prevention of type 2 diabetes mellitus in the Diabetes Prevention Program. Diabetes Care, 2003; 26 (1): 36-47. 

PubMed ID: 12502656
Study Design:
Randomized Controlled Trial; Cost-Effectiveness Analysis
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
  • To describe the costs associated with the primary prevention of type 2 diabetes in the DPP
  • To help health systems and policy makers to translate the results of the DPP into efficient clinical and public health practice
  • To provide the basis for studies of the cost-effectiveness of the DPP interventions. 
Inclusion Criteria:
  • Impaired glucose tolerance (fasting plasma glucose, 95mg to 125mg per dL; plasma glucose, 140mg to 199mg per dL two hours after 75-gram oral glucose load)
  • At least 25 years
  • BMI at least 24kg/m2.
Exclusion Criteria:

Not reported.

Description of Study Protocol:
  • Recruitment: Recruitment methods not reported
  • Design: Cost-effectiveness analysis from DPP randomized controlled intervention trials
  • Intervention: Placebo vs. metformin vs. intensive lifestyle intervention over three years.

Statistical Analysis

  • Costs calculated as unit costs to resources used, on both perspectives of large health system and of society
  • Direct medical (including identifying IGT, intervention costs, follow-up over three years; care outside of DPP trial); direct non-medical (patient out-of-pocket cost of food, transportation; cost of patient time in attending appointments, travel to appointments, exercising, shopping, cooking); indirect costs (patient loss of time from work, school, usual activities as result of DPP visits, illness, injury).
Data Collection Summary:

Timing of Measurements

Trial period lasted three years.

Dependent Variables

  • Direct medical cost
  • Direct non-medical costs
  • Indirect costs.

Independent Variables

  • Placebo
  • Metformin
  • Intensive lifestyle intervention.



Description of Actual Data Sample:
  • Initial N: 3,234 participants (68% female)
  • Attrition (final N): Not reported
  • Age: Mean 51 years
  • Ethnicity: 45% minority
  • Anthropometrics: Mean BMI, 34kg/m2
  • Location: DPP Coordinating and Biostatistics Centers, George Washington University, Rockville, Maryland, USA.
Summary of Results:


Variables (Over Three Years) Placebo Metformin Intensive Lifestyle Intervention
Direct Medical Cost of Interventions
Direct per Capital Medical Cost of Care
Outside DPP ($) 

(-272 vs. placebo)

(-432 vs. placebo)

Per Capita Direct Non-Medical ($)

(-9 vs. placebo)

(+1445 vs. placebo)

Indirect Cost ($)

(+230 vs. placebo)

(-174 vs. placebo)

Cost per Patient, Health System Perspective
(Relative to Placebo; $)
Cost per Patient, Societal Perspective
(Relative to Placebo; $)

Other Findings

  • The direct medical cost of laboratory tests to identify one subject with impaired glucose tolerance was $139
  • Over three years, the direct medical costs of the interventions were $79 per participant in the placebo group, $2,542 in the metformin group, and $2,780 in the lifestyle group
  • The direct medical costs of case outside the DPP were $272 less per participant in the metformin group and $432 less in the lifestyle group compared with the placebo group
  • Direct non-medical costs were $9 less per participant in the metformin group and $1,445 greater in the lifestyle group compared with the placebo group
  • Indirect costs were $230 greater per participant in the metformin group and $174 less in the lifestyle group compared with the placebo group
  • From the perspective of a health system, the cost of the metformin intervention relative to the placebo intervention was $2,191 per participant and the cost of the lifestyle intervention was $2,269 per participant over three years
  • From the perspective of society, the cost of the metformin intervention relative to the placebo intervention was $2,412 per participant and the cost of the lifestyle intervention was $3,540 per participant over three years
  • The Metformin (additional cost of non-generic medication) and lifestyle (additional cost of staff time used for counseling, monitoring of adherence) interventions were more expensive than placebo 
  • Lifestyle intervention, though 36% more expensive than metformin at year one, ended up being 7% less expensive than metformin by year three. 
Author Conclusion:

The metformin and lifestyle interventions are associated with modest incremental costs compared with the placebo intervention. The evaluation of costs relative to health benefits will determine the value of these interventions to health systems and society. 

Funding Source:
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) 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? 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? N/A
  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? 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
  5.3. 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? 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? 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)? N/A
  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? ???
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