|An evaluation of cost sharing to finance a diet and physical activity intervention to prevent diabetes
|Ackermann R T, Marrero D G, Hicks K A, Hoerger T J, Sorensen S, Zhang P, Engelgau M M, Ratner R E, Herman W H
This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn.
The present study compared the cost-effectiveness of the Diabetes Prevention Program (DPP) lifestyle intervention starting at age 65 compared to placebo, with the DPP starting at age 50 compared to placebo. The intervention was for the prevention of type 2 diabetes in people with impaired glucose tolerance (IGT). The primary intervention comprised a combination of diet and moderate-intensity physical activity, such as brisk walking. The programme included a one-on-one, 16-lesson core curriculum, followed by monthly maintenance visits that included both group sessions and one-on-one visits with case managers. Placebo participants received standard lifestyle recommendations through an annual 30-minute education session. Details of the DPP lifestyle intervention are given elsewhere (Diabetes Prevention Program Research Group 2002, see 'Other Publications of Related Interest' below for bibliographic details).
The target population of the model was that of the DPP, which enrolled 3,234 participants with IGT who were at least 25 years of age and had a body mass index of at least 24 kg/m2. At baseline, the participants had a mean age of 51 years, 68% were women, and 45% were non-white. Details are given elsewhere (Knowler et al. 2002, see 'Other Publications of Related Interest' below for bibliographic details).
The setting for the study was outpatient and inpatient care. The economic evaluation was set in the USA.
Dates to which data relate
The effectiveness data used in the model came from studies published between 1998 and 2005. The cost data were from 2003. The price year was 2000.
A Markov state transition model was used to assess the lifetime progression from IGT to diabetes to complications and death (Knowler et al. 2002 and Centers for Disease Control Diabetes Cost-Effectiveness Group 2002, see 'Other Publications of Related Interest' below for bibliographic details). The health states were clearly reported and a number of modelling assumptions were fully justified. Details of the model parameters are available in an online web appendix. Several scenarios were evaluated. The first scenario applied the lifestyle intervention to participants with IGT at age 50 years. The second was conducted in order to estimate differences in health and economic outcomes resulting from a 15-year delay in offering the intervention. Finally, a third analysis was performed to explore cost-sharing strategies across different health payers when individuals, aged between 50 and 64, received health care coverage from a private insurer, and a later period beyond age 64 when recipients were Medicare eligible.
Study designs and other criteria for inclusion in the review
The clinical and epidemiological data included the annual hazard of diabetes onset and the risk reduction due to the lifestyle intervention. Model parameters for the development of diabetes, complications, and death for adults with IGT or undiagnosed (preclinical) diabetes, were reported in an online appendix.
Sources searched to identify primary studies
Data were taken mainly from the DPP and other sources (Knowler et al. 2002, Diabetes Prevention Program Research Group 2002, Centers for Disease Control Diabetes Cost-Effectiveness Group 2002). Intensive glycaemic management and changes in glycated haemoglobin and diabetes treatments were taken from published literature (UK Prospective Diabetes Study 1998, see 'Other Publications of Related Interest' below for bibliographic details).
Methods used to derive estimates of effectiveness
The process used to identify the data was not reported. No inclusion criteria were specified for any parameters. The method used to select the estimates was neither reported nor discussed.
Measure of benefits used in the economic analysis
The authors used quality-adjusted life-years (QALYs) as a measure of benefit. Health utility scores were taken from the DPP and were collected annually from study participants using the self-administered quality of well-being index. For people with IGT who developed diabetes, an empirically derived, additive prediction model was used; this estimated quality of well-being index scores by applying penalty scores for demographic, treatment and disease state variables to a baseline health utility score. A similar estimation was applied for those developing hypertension, coronary heart disease or cardiovascular disease before developing diabetes. The benefits were discounted at an annual rate of 3%.
DPP data were used to estimate annual non-intervention direct medical costs for people with IGT who did not develop diabetes within 3 years. To estimate costs beyond the DPP trial, it was assumed that year 3 costs would be incurred each year until individuals developed diabetes or died. The direct medical costs included hospital, emergency room, urgent care and outpatient services, as well as costs of prescription medications and telephone calls to health care providers. For people who developed diabetes, annual direct medical costs were adjusted by demographic characteristics, diabetes and hypertension treatments, and the acute and ongoing costs of microvascular and macrovascular complications. Similar adjustments were performed for people who developed non-diabetes complications before developing diabetes with no cardiovascular risk factors or microvascular, neuropathic or cardiovascular complications. Discounting was performed at an annual rate of 3%. The price year was 2000. No further details were provided.
Statistical analysis of costs
No statistical analyses of the quantities or costs were conducted as the data were deterministic.
Productivity costs were not included in the analysis.
Recent extensive sensitivity analyses had shown that the lifetime incremental cost-effectiveness ratio for the DPP lifestyle intervention remained attractive across wide ranges of intervention adherence and effectiveness, duration of preclinical diabetes and discount rate (Herman et al. 2005, see 'Other Publications of Related Interest' below for bibliographic details). The authors did not repeat these analyses but decided to explore three different scenarios: the effect of modelling the lifestyle intervention as a group-delivery model; a scenario in which the intervention was only 50% as effective as in the DPP but cost the same; and a scenario in which 10% of eligible participants dropped out of the programme each year. In this scenario, it was assumed that 50% of people who remained eligible would participate at age 65 if Medicare offered the programme free of charge.
Estimated benefits used in the economic analysis
The lifetime health benefits of the lifestyle intervention compared with placebo were as follows.
For people initiating the intervention at age 50 years, the lifetime risk for developing diabetes was reduced from 86.7% to 65.4%.
A 15-year delay in the intervention increased the lifetime risk for developing diabetes from 65.4 to 83.2%, and the risk reduction attributable to the intervention decreased from 22% to only 4%.
The lifetime QALYs were 10.68 for the placebo intervention, 11.27 for people initiating the DPP lifestyle intervention at age 50 years, and 10.83 for the DPP lifestyle intervention delayed until age 65.
The incremental QALYs versus placebo were 0.59 for the DPP starting at age 50 and 0.27 for the DPP starting at age 65.
Lifetime direct medical costs were $52,321 for the placebo intervention, $53,079 for people initiating the DPP lifestyle intervention at age 50 years, and $52,552 for the DPP lifestyle intervention delayed until age 65.
The incremental costs versus placebo were $758 for the DPP starting at age 50 and $231 for the DPP starting at age 65.
Synthesis of costs and benefits
The incremental costs per QALY gained versus placebo were $1,288 for people initiating the DPP lifestyle intervention at age 50 years and $1,575 for the DPP lifestyle intervention delayed until age 65.
After age 65, the direct medical costs were $2,136 lower for participants who began the intervention at age 50, compared with placebo recipients.
For the private payer, these benefits were associated with a 15-year incremental cost of $2,894 and an incremental cost-effectiveness of $9,647 per QALY gained.
In terms of the full economic evaluation which compared the cost-effectiveness of the provision of the Diabetes Prevention Program (DPP) lifestyle intervention starting at age 65 compared to placebo with the DPP starting at age 50 compared to placebo, the DPP could prevent 37% of new cases of diabetes before age 65, at a cost of $1,288 per quality-adjusted life-year (QALY) gained. The cost-sharing conclusions were independent of the full economic evaluation.
CRD COMMENTARY - Selection of comparators
A justification was given for the comparator used, mainly that no intervention programme was implemented in the authors' setting. You should decide if the comparator represents current practice in your own setting.
Validity of estimate of measure of effectiveness
The authors combined data from existing models with data from several published studies of varying designs. No systematic search for data was reported, which could be an important limitation. The parameters for the model were derived from published studies and are available in an online web appendix.
Validity of estimate of measure of benefit
The estimation of health benefits (QALYs) was derived using a Markov model. Utility weights incorporated in the model and their methods were clearly described, as originally derived from the published studies.
Validity of estimate of costs
Since an insurer perspective was reported all the relevant cost categories, as well as their costs, were taken into consideration. The resource use data and unit costs were not reported separately, which would make it difficult to rework the analysis for other settings. The price year and the sources of the costs were adequately reported. The costs were discounted at an annual rate of 3%, which was appropriate given that the time horizon was longer than 1 year. The reflation or deflation of costs from different dates was not reported. Sensitivity analyses of costs were reported elsewhere.
The full economic evaluation was not the main objective of the study, which was more of a financial analysis used to inform cost-sharing options. The authors' conclusions about the full economic evaluation reflected the scope of the analysis.
Implications of the study
The implications of the full economic evaluation are that cost-sharing options should be investigated in order to obtain the health benefits from starting the DPP at the age of 50 rather than at the age of 65.
Source of funding
Supported by the Centers for Disease Control and Prevention, RTI International and the Indiana University School of Medicine.
Ackermann R T, Marrero D G, Hicks K A, Hoerger T J, Sorensen S, Zhang P, Engelgau M M, Ratner R E, Herman W H. An evaluation of cost sharing to finance a diet and physical activity intervention to prevent diabetes. Diabetes Care 2006; 29(6): 1237-1241
Other publications of related interest
Because readers are likely to encounter and assess individual publications, NHS EED abstracts reflect the original publication as it is written, as a stand-alone paper. Where NHS EED abstractors are able to identify positively that a publication is significantly linked to or informed by other publications, these will be referenced in the text of the abstract and their bibliographic details recorded here for information.
The Diabetes Prevention Program Research Group. The Diabetes Prevention Program (DPP): description of lifestyle intervention. Diabetes Care 2002;25:2165-71.
Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002;346:393-403.
The Centers for Disease Control Diabetes Cost-Effectiveness Group. Cost-effectiveness of intensive glycemic control, intensified hypertension control, and serum cholesterol level reduction for type 2 diabetes. JAMA 2002;287:2542-51.
UK Prospective Diabetes Study (UKPDS) Group. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet 1998;352:837-53.
Herman WH, Hoerger TJ, Brandle M, Hicks K, Sorensen S, Zhang P, et al. The cost-effectiveness of lifestyle modification or metformin in preventing type 2 diabetes in adults with impaired glucose tolerance. Ann Intern Med 2005;142:323-32.
Subject indexing assigned by NLM
Aged; Cost Sharing; Diabetes Mellitus /economics /prevention & Diet /economics; Disease Progression; Exercise; Glucose Intolerance /economics; Health Status; Humans; Life Style; Medicare; Middle Aged; Probability; United States; control
Date bibliographic record published
Date abstract record published