The Cost-Effectiveness of GP Led Behavioural Change Involving Weight Reduction: Implications for the Prevention of Diabetes

The purpose of this paper is to examine from a societal perspective, the relative cost-effectiveness of diabetes prevention through promotion of behavioural change by GPs, compared to current GP practice. For policy and practical relevance, the initiative is examined as a stand-alone program, as well as nested within the context of a public health program for the reduction of cardiovascular disease(CVD). The `piggy-backed' design reflects the joint risk factors shared by non-insulin dependent diabetes mellitus (NIDDM) and CVD, together with significant cost savings and, potentially, improved rates of participation and adherence. Results are compared to recent cost-effectiveness findings for NIDDM prevention through media campaigns and other settings (weight loss clinics and the workplace). Methods A hypothetical NIDDM program is evaluated, where estimated costs are based upon recent trials of multiple risk factor reduction programs in Australia. Program effectiveness in reducing Body Mass Index (BMI), the impact of that weight reduction on the incidence of NIDDM, and the associated mortality effects, are drawn from a survey of studies reported in the literature on dietary and lifestyle change. The value of health care savings from a fall in NIDDM is estimated and deducted from program cost to provide an estimate of the net cost of the NIDDM initiative. Central to the methodology is disease modelling incorporating the literature findings. A simple Markov model has been utilised, which includes age specific all-cause mortality estimates adjusted for overweight and metabolic status. Available evidence on current practice suggests that preventive care within GP consultations is provided to approximately 22% of those who are overweight (BMI > 24.9), with verbal advice being the most usual approach. Screening for associated pathology occurs infrequently, either for cholesterol levels (6% of eligible patients) or NIDDM (25% of eligible patients). The benefits of current weight related preventive activity are assumed to be reflected in the current incidence of NIDDM. The annual cost of care for current cases of NIDDM has been estimated at $1,800 per patient. The costs and benefits of current practice are deducted from the costs and benefits of the NIDDM program to provide the incremental impact of the new initiative. Results Using a 5% discount rate, net incremental cost per life year saved is estimated to be approximately $63,000, if implemented as an independent program, or $4,000 if piggy-backed onto a CVD intervention. One of the problems in considering the efficiency of the hypothetical NIDDM program evaluated is the great variability in results. Sensitivity analysis reveals a wide range of outcomes under varied but plausible assumptions. For the NIDDM program run in `stand-alone' mode, cost-effectiveness varies from $96,000 per life year through to $18,500 per life year. In other words, the hypothetical NIDDM program could be excellent value-for-money or a white elephant. Such variability casts particular importance on understanding the nature and predictability of the program's costs and outcomes. While some cost containment measures can improve efficiency (`piggy-backing' the program, reducing set-up costs and overheads, use of nurses in patient recruitment), others can dramatically reduce efficiency (ie decreasing GP participation). Apart from the stand-alone/piggy-backing decision and reduced set-up costs, the major improvements in efficiency all come from improvements in effectiveness. The extent of GP participation, patient recruitment criteria and participation rates, as well as the level and duration of weight loss are all major determinants. Of these factors, GP participation and patient selection criteria seem the most amenable to improvement through program design. The extent and duration of weight loss will be harder to control. The results suggest that irrespective of what improvements are achieved in GP participation and in the economy of program establishment, the share of program funding that is likely to go into program establishment and management, should focus attention on what potential exists for co-ordinating related health promotion campaigns that address shared or related risk factors, and in better utilising existing infrastructure (such as Divisions of General Practice). Comparison with other NIDDM primary prevention programs suggests that some caution is warranted in encouraging general practitioners into behavioural modification programs. The results of our study suggest that an economic case for their involvement is yet to be demonstrated. This is consistent with the findings of other researchers on promoting lifestyle change in general practice (Ashenden et al. 1995; Salkeld et al. 1995). The answer to the question of whether GP-led behavoural change for weight reduction is `value-for-money' is therefore: `possibly, but proceed with caution'. The analysis suggests that smaller health gains achieved over a more broadly defined `at risk' group (ie only requiring one risk factor, such as overweight) is more cost-effective than larger gains achieved for a more selectively defined `at risk' group (ie overweight plus second CVD risk factor). Further, despite the impact of discounting, weight loss maintained over a long period (ie 25 years) is more cost-effective than larger weight loss achieved for shorter periods (ie 5 years). This confirms the view that lifestyle changes that can be sustained over the longer period are better than dramatic changes that cannot be sustained. It also suggests that more effort should be put in to the maintenance of newly acquired healthy behaviours, vis-a-vis effecting the change in the first place. Finally, while recipients of new health promotion initiatives often receive subsidised services and pay a lower percentage of total program costs than under the `status quo', it is often forgotten that in absolute terms they are being asked to give more and maintain it over longer periods. Failure to recognise the absolute/relative cost differential may lead to unrealistic expectations of patient compliance and health cost offsets.