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Effectiveness and Cost-Effectiveness of Diabetes Prevention Among Adherent Participants
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Effectiveness and Cost-Effectiveness of Diabetes Prevention Among Adherent Participants

William H. Herman, MD, MPH; Sharon L. Edelstein, ScM; Robert E. Ratner, MD; Maria G. Montez, RN, MSHP; Ronald T. Ackermann, MD, MPH; Trevor J. Orchard, MD; Mary A. Foulkes, PhD; Ping Zhang, PhD; Christopher D. Saudek, MD†; and Morton B. Brown, PhD; The Diabetes Prevention Program Research Group
Over 10 years, among adherent participants, lifestyle intervention and metformin were effective and cost-effective for diabetes prevention compared with placebo.
In these analyses, from a health system perspective and without discounting, lifestyle, DPP group lifestyle, and metformin were all cost saving relative to placebo. In our previous undiscounted intent-to-treat analysis, lifestyle cost approximately $6700 per QALY gained compared with placebo but both DPP group lifestyle and metformin were cost saving.2 In both this analysis and our previous intent-to-treat analysis, lifestyle was more expensive than metformin but produced greater health benefits.2 The undiscounted cost per QALY was $14,213 and $10,555, respectively.2 In these analyses, from a health system perspective and with both costs and QALYs discounted at 3%, neither lifestyle, DPP group lifestyle, nor metformin was cost saving. These differences likely reflect the impact of discounting on early treatment costs. In these analyses, we assumed that all participants randomized to lifestyle and metformin remained adherent during the first year. Because early treatment costs were greater, discounting resulted in the early, relatively expensive preventive interventions being less cost-effective.

The results of this 10-year within-trial analysis demonstrate that lifestyle and metformin interventions are even more effective for diabetes prevention in DPP/DPPOS participants who are adherent to their randomized treatments than among the larger group of both adherent and nonadherent participants. In addition, the interventions are extremely cost-effective or even cost saving. These results are consistent with earlier analyses that assessed the cost-effectiveness of lifestyle and metformin interventions based upon the results of the Finnish Diabetes Prevention Study,15 the DPP,16,17 the DPP/DPPOS,18 and the Indian Diabetes Prevention Study.19 One study which did not find lifestyle intervention to be costeffective20 differed from the published lifetime cost-utility analyses16-18 in that it assumed that the lifestyle intervention continued over the participants’ lifetimes even after they developed diabetes. It also assumed that when participants developed diabetes, their A1C remained <7.0% for the remainder of their lives. These assumptions led to potential overestimation of intervention costs and underestimation of the costs and quality-of-life impact of the complications and comorbidities of diabetes. Taken together, these assumptions likely account at least in part for the difference in results.

This analysis has a number of limitations. First, in defining participants as adherent to the lifestyle intervention, we used the outcome (weight loss) to define adherence. This was necessary because all lifestyle participants were strongly encouraged to attend lifestyle sessions and attendance was not a good marker of adoption of the behavioral intervention. Second, the simulated group lifestyle intervention was not empirically tested within the DPP. The decision to implement the lifestyle intervention individually within DPP was pragmatic. The study group was anxious to enroll participants and begin the interventions as quickly as possible. The literature suggests, however, that group-implemented lifestyle interventions are at least as effective as individually implemented interventions, largely due to the benefits of peer support. Third, we included all participants randomized to placebo in these analyses. During DPPOS, placebo participants were offered and participated in the group lifestyle intervention and 3% were prescribed metformin outside the study. If these interventions were effective in the placebo group, they would have reduced non–intervention- related resource utilization and costs. The relative impact of these potential biases is impossible to determine, but if the intervention costs were less than the savings resulting from a decreased incidence of diabetes, the bias would be conservative, making lifestyle and metformin appear less cost-effective relative to placebo.

In summary, this assessment of outcomes among DPP/DPPOS participants who were adherent to their randomized treatment assignments indicates that lifestyle and metformin are likely to be even more effective in real-world clinical practice than they were during the randomized controlled clinical trial and its subsequent observational follow-up study. Perhaps not surprisingly, the costs of the interventions, especially the cost of the metformin intervention, were higher among adherent participants, but the benefits, assessed in terms of non–intervention-related direct medical costs, were also greater. Interestingly, the benefits in terms of QALYs gained were similar among adherent and intent-to-treat participants, perhaps reflecting the impact of non–diabetes-related comorbidities on quality of life. The impact of discounting on the cost-effectiveness equation highlights the fact that in chronic diseases, prevention is an important investment but often not cost saving in the short term.21 To the extent that intervention costs are accrued early in the natural history of disease and complications are accrued later, discounting tends to portray a less favorable cost-effectiveness picture. Nevertheless, these analyses confirm that lifestyle, group lifestyle, and metformin represent a good value for money.

Acknowledgments
The Research Group gratefully acknowledges the commitment and dedication of the participants of the DPP and DPPOS. During the DPPOS, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) of the National Institutes of Health provided funding to the clinical centers and the Coordinating Center for the design and conduct of the study, and collection, management, analysis, and interpretation of the data. The Southwestern American Indian Centers were supported directly by the NIDDK, including its Intramural Research Program, and the Indian Health Service. The General Clinical Research Center Program, National Center for Research Resources, supported data collection at many of the clinical centers. Funding was also provided by the National Institute of Child Health and Human Development, the National Institute on Aging, the National Eye Institute, the National Heart Lung and Blood Institute, the Office of Research on Women’s Health, the National Center for Minority Health and Human Disease, the Centers for Disease Control and Prevention, and the American Diabetes Association. Bristol-Myers Squibb and Parke-Davis provided additional funding and material support during the DPP, Lipha (Merck-Sante) provided medication, and LifeScan Inc donated materials during the DPP and DPPOS. Economic analyses were supported in part by the Michigan Diabetes Research and Training Center (P60 DK020572) and the Michigan Center for Diabetes Translational Research (P30 DK092926). The opinions expressed are those of the investigators and do not necessarily reflect the views of the funding agencies. A complete list of Centers, investigators, and staff can be found in the eAppendix.


Author Affiliations: From Department of Endocrinology (WHH), University of Michigan, Ann Arbor, MI; Biostatistics Center (SLE), George Washington University, Rockville, MD; Medstar Research Institute (RER), Washington, DC; Department of Medicine (MGM), University of Texas Health Science Center, San Antonio, TX; Department of Medicine (RTA), Indiana University School of Medicine, Indianapolis, IN; University of Pittsburgh (TJO), Pittsburgh, PA; Biostatistics Center (MAF), George Washington University, Rockville, MD; Centers for Disease Control and Prevention (PZ), Atlanta, GA; Department of Internal Medicine (MBB), University of Michigan, Ann Arbor, MI; Biostatistics Center (Research Group DPP), George Washington University, Rockville, MD; John Hopkins University School of Medicine (CDS), Baltimore, MD.
Deceased.


Funding Source: NIH 5U01-DK048375-12.


Author Disclosures: Dr Ratner reports that he has received consulting fees from Novo Nordisk and sanofi. Dr Orchard reports that he has received consulting fees from Abbott Laboratories and lecture fees from Gilead. The other authors (WHH, SLE, MGM, RTA, MAF, PZ, MBB) report no relationship or financial interest with any entity that would pose a conflict of interest with the subject matter of this article.


Authorship Information: Concept and design (WHH, SLE, RER, MGM, RTA, TJO, MAF, PZ, CDS); acquisition of data (WHH, RER, MGM, TJO); analysis and interpretation of data (WHH, SLE, RER, MAF, PZ, MBB); drafting of the manuscript (WHH, SLE, RTA, MAF); critical revision of the manuscript for important intellectual content (WHH, SLE, RTA, RER, TJO, MAF, PZ); statistical analysis (SLE, MAF, MBB); provision of study materials or patients (WHH, RER, MGM, TJO, CDS); obtaining funding (WHH, TJO, CDS); administrative, technical, or logistic support (WHH, TJO); and supervision (WHH, MGM, MAF).


Address correspondence to: The Diabetes Prevention Program Coordinating Center, George Washington University Biostatistics Center, 6110 Executive Blvd, Ste 750, Rockville, MD 20852. E-mail: dppmail@biostat.bsc.gwu.edu.
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