An update on the Diabetes Prevention Program

Abstract

Objective: To summarize the results of the Diabetes Prevention Program (DPP) and describe the additional 5-year follow-up study.

Methods: The design, implementation, and outcome of the DPP are reviewed, and an economic analysis of the effects of diabetes prevention and delay is presented.

Results: The DPP, thus far the largest diabetes prevention trial with the most ethnically diverse patient population, originally consisted of more than 3,800 subjects with impaired glucose tolerance. These subjects were randomized to receive one of four interventions: intensive lifestyle adjustments or standard lifestyle plus one of the following--placebo, metformin, or troglitazone. In June 1998, the troglitazone treatment was discontinued after a fatal case of liver failure in a study participant, but the subjects in this arm of the study continued to undergo followup. Thus, 3,234 subjects remained in the other three arms of the study. After a mean of 2.8 years of follow-up, the DPP was prematurely terminated because of an observed significant benefit to the intervention groups. Both metformin therapy and intensive lifestyle intervention reduced the risk of developing diabetes (by 31% and 58%, respectively, in comparison with placebo), and both interventions were deemed to be cost-effective on the basis of computer projections over a lifetime. Because of the premature discontinuation of the DPP, the durability of the interventions on diabetes prevention and the effect on microvascular and macrovascular disease could not be assessed. The subsequent outcomes study will address these issues during a 5-year follow-up period.

Conclusion: The DPP showed that both metformin and intensive lifestyle modifications effectively delayed or prevented the development of diabetes in a cost-effective manner.

Fig. 1

Cumulative incidence of diabetes, stratified by treatment group, for the four-arm Diabetes Prevention Program, including the troglitazone treatment group (N = 2,343). Troglitazone (TROG) versus placebo (PLAC), P<0.001; troglitazone versus metformin (MET), P = 0.02; troglitazone versus intensive lifestyle (ILS), P = 0.18. Adapted from Knowler et al (Diabetes Prevention Program Research Group) (6).

Fig. 2

Computer modeling of Diabetes Prevention Program interventions and outcomes over a lifetime, based on the assumption that interventions are applied until the subjects die and the results are consistent with the observations during the randomized trial. IGT = impaired glucose tolerance; solid line = placebo; dashed line = metformin; dotted line = intensive lifestyle intervention. Adapted from Herman et al (Diabetes Prevention Program Research Group) (10).