Intervention-only programmes were in general more cost effective than programmes that also included a screening component .
The longer the period evaluated , the more cost-effective interventions appeared .
There was insufficient evidence to answer the question of ( 1 ) whether lifestyle programmes are more cost effective than metformin or ( 2 ) whether low-intensity lifestyle interventions are more cost effective than the more intensive lifestyle programmes that were tested in trials .
OBJECTIVE Explore the cost-effectiveness of lifestyle interventions and metformin in reducing subsequent incidence of type 2 diabetes  , both alone and in combination with a screening programme to identify high-risk individuals .
The Cost-Effectiveness of Lifestyle Modification or Metformin in Preventing Type 2 Diabetes in Adults with Impaired Glucose Tolerance
Context The Diabetes Prevention Program ( DPP ) showed that lifestyle changes or metformin effectively decreased the development of  type 2 diabetes in adults with impaired glucose tolerance . The economics of these interventions is important to policymakers . Contribution This cost-effectiveness model estimates that the DPP life-style intervention would cost society about $ 8800 and metformin would cost about $ 29900 per quality -adjusted life-year saved . While lifestyle intervention had a favorable cost-effectiveness profile at any adult age , metformin was not cost-effective after age 65 years . Implication s The cost-effectiveness of lifestyle intervention to prevent type 2 diabetes  in high-risk individuals is within the range that American society typically finds acceptable for health care interventions . The Editors During the past half century , the number of persons with diagnosed diabetes in the United States has increased 4- to 6-fold ( 1 ) . Recent large clinical trials from Asia , Europe , and North America have demonstrated that behavioral and medication interventions can delay or prevent the development of type 2 diabetes in persons with impaired glucose tolerance , which is defined by a plasma glucose level between 7.77 mmol/L ( 140 mg/dL ) and 11.04 mmol/L ( 199 mg/dL ) 2 hours after a 75-g oral glucose load ( 2 - 6 ) . The Diabetes Prevention Program ( DPP ) r and omly assigned 3234 nondiabetic persons 25 years of age or older with impaired glucose tolerance and fasting glucose levels between 5.27 mmol/L ( 95 mg/dL ) and 6.94 mmol/L ( 125 mg/dL ) to placebo ; a lifestyle-modification program with the goals of at least a 7 % weight loss and 150 minutes of physical activity per week ; or metformin , 850 mg twice daily ( 4 ) . The mean age of participants was 51 years , and the mean body mass index was 34.0 kg/m2 ; 68 % were women and 45 % were members of minority groups ( 4 ) . The average follow-up was 2.8 years . Compared with the placebo intervention , the lifestyle intervention reduced the incidence of type 2 diabetes by 58 % and the metformin intervention reduced the incidence of type 2 diabetes by 31 % ( 4 ) . We have previously described the costs of the DPP interventions and their cost-effectiveness within the 3-year trial period ( 7 , 8) . In this analysis , we project the costs , health outcomes , and cost-effectiveness of the DPP lifestyle and metformin interventions over a lifetime relative to the placebo intervention . Methods Clinical Trial The lifestyle intervention involved a healthy , low-calorie , low-fat diet and moderate physical activity , such as brisk walking . The lifestyle intervention was implemented with a 16-lesson core curriculum covering diet , exercise , and behavior modification that was taught by case managers on a one-on-one basis , followed by individual sessions ( usually monthly ) and group sessions with case managers ( 9 ) . At the end of the study , 38 % of participants in the lifestyle intervention group had lost at least 7 % of their initial body weight .  The metformin and placebo interventions were initiated at a dosage of 850 mg once a day . At 1 month , the dosage of metformin or placebo was increased to 850 mg twice daily . Case managers reinforced adherence during individual quarterly sessions ( 10 ) . At the end of the study , 72 % of participants in the metformin intervention group and 77 % of participants in the placebo intervention group took at least 80 % of the prescribed dose . All participants received st and ard lifestyle recommendations through written information and an annual 20- to 30-minute individual session that emphasized the importance of a healthy lifestyle ( 10 ) . Simulation Model We assessed the progression from impaired glucose tolerance to onset of diabetes to clinical ly diagnosed diabetes to diabetes with complications and death by using a lifetime simulation model originally developed by the Centers for Disease Control and Prevention and Research Triangle Institute International . The model has a Markov structure and includes annual transition probabilities between disease states ( 11 ) . In addition to disease progression , the model tracks costs and quality -adjusted life-years ( QALYs ) . The model has been described elsewhere ( 11 ) . For our analyses , we modified the model to include data from the DPP on progression , costs , and quality of life associated with impaired glucose tolerance , data from the United Kingdom Prospect i ve Diabetes Study ( UKPDS ) on diabetes progression and complications , and new data on cost and quality of life associated with diabetes . A technical report describing the model is available . Supplement . Technical Report Disease Progression , Complications , and Comorbid Conditions Impaired Glucose Tolerance to Onset of Type 2 Diabetes We analyzed data from the DPP to assess the annual hazard of diabetes onset in the lifestyle , metformin , and placebo intervention groups . For patients receiving the placebo intervention , the annual hazard of diabetes onset was 10.8 per 100 person-years . At 3 years of follow-up , the risk reductions for the lifestyle and metformin interventions were 55.8 % and 29.9 % , respectively . In the base-case analysis , we assumed that the lifestyle and metformin interventions would be applied until diabetes onset and that the health and quality -of-life benefits associated with the interventions persisted until diabetes onset . Complications and Comorbid Conditions Associated with Impaired Glucose Tolerance We analyzed data from the DPP and other published sources to assess the prevalence of complications and comorbid conditions in participants with impaired glucose tolerance . At baseline , 6.0 % of DPP participants had microalbuminuria and 0.4 % had nephropathy .  The DPP did not measure peripheral neuropathy , but previous studies found that the prevalence of neuropathy in persons with impaired glucose tolerance was 74 % of that in persons with newly diagnosed type 2 diabetes ( 12 ) and 12.3 % of persons with newly diagnosed type 2 diabetes have neuropathy ( 13 ) . Therefore , we assumed that at baseline , 8.5 % of DPP participants had clinical neuropathy . At baseline , 28 % of DPP participants had hypertension , 45 % had dyslipidemia , 7 % were smokers , 1.1 % had a history of cerebrovascular disease , and 2.0 % had a history of myocardial infa rct ion . No other complications were present . We assumed that during impaired glucose tolerance , microvascular or neuropathic complications would not progress . We assumed that hypertension and dyslipidemia developed at the rates observed in the DPP . On the basis of 2 large studies ( 14 , 15 ) , we assumed that the incidences of coronary heart disease and cerebrovascular disease in patients with impaired glucose tolerance were 58 % and 56 % , respectively , of those observed in patients with type 2 diabetes . We further assumed that nondiabetes-related mortality for persons with impaired glucose tolerance was the same as for persons with diabetes ( 16 ) . Onset of Type 2 Diabetes to Clinical Diagnosis of Type 2 Diabetes In the DPP , participants were tested for diabetes every 6 months ; diabetes was diagnosed at onset . In routine clinical practice , type 2 diabetes is estimated to develop 8 to 12 years before its clinical diagnosis ( 17 , 18 ) . In our base-case analysis , we therefore assumed that a 10-year delay occurred between the onset and clinical diagnosis of diabetes . Participants in the DPP  had a mean hemoglobin A1c level of 6.4 % at the onset of diabetes . Participants in the UKPDS had a mean hemoglobin A1c of 7.1 % after a dietary run-in period but before r and omization ( 13 ) . Both DPP placebo participants and UKPDS participants received st and ard lifestyle recommendations . Accordingly , we assumed that during the 10-year interval between onset and clinical diagnosis of diabetes , patients were treated for type 2 diabetes and that hemoglobin A1c level increased at 0.07 % per year from 6.4 % to 7.1 % . Complications and Comorbid Conditions Associated with Undiagnosed Diabetes We further assumed that between onset and clinical diagnosis of diabetes , microvascular and neuropathic complications progressed slowly , such that by clinical diagnosis of type 2 diabetes , their prevalence reached the level observed in the UKPDS cohort at r and omization ( 13 , 19 , 20 ) . We assumed that blood pressure and lipid levels progressed as they did in DPP participants and that cardiovascular complications occurred as they would in type 2 diabetes according to risk factors and hemglobin A1c level ( 21 , 22 ) . Clinical Diagnosis of Type 2 Diabetes to Diabetes with Complications and Death We assumed that after clinical diagnosis , all persons with type 2 diabetes received intensive glycemic management as described in the UKPDS ( 13 ) . We modeled changes in hemoglobin A1c and diabetes treatments to reflect those observed in the UKPDS intensive therapy group . We based risk for retinopathy progression on UKPDS 38 ( 23 ) , risk for nephropathy progression on UKPDS 64 ( 20 ) , and risk for neuropathy progression on UKPDS 33 ( 13 ) . We based risk for cerebrovascular disease on UKPDS 60 ( 22 ) and risk for coronary heart disease on UKPDS 56 ( 21 ) . Costs Costs of Impaired Glucose Tolerance To estimate the total direct medical costs of impaired glucose tolerance , we considered the costs of the DPP interventions ( the cost of identifying participants , implementing and maintaining the interventions , and monitoring and treating the side effects of the interventions ) and the costs of the medical care outside the DPP ( 7 ) . In analyses from the perspective of society , we included both direct medical costs and direct nonmedical costs . We did not include indirect costs because they are captured in the assessment of QALYs ( 24 ) . Table 1 shows the total direct medical costs by treatment group , sex , and year in the DPP ( 7 ) . Costs were higher in the lifestyle and metformin interventions than in the placebo intervention and higher in women than in men . Costs decreased over time in all 3 intervention groups but after year 1 tended to decrease more in the lifestyle than
Intervention-only programmes were in general more cost effective than programmes that also included a screening component .
The longer the period evaluated , the more cost-effective interventions appeared .
There was insufficient evidence to answer the question of ( 1 ) whether lifestyle programmes are more cost effective than metformin or ( 2 ) whether low-intensity lifestyle interventions are more cost effective than the more intensive lifestyle programmes that were tested in trials .
OBJECTIVE Explore the cost-effectiveness of lifestyle interventions and metformin in reducing subsequent incidence of type 2 diabetes  , both alone and in combination with a screening programme to identify high-risk individuals .