The role of public health models in policy making.

Aims: To evaluate the use of public health models in policymaking, with regard to the appropriateness and the practicalities of using such models for simulating health interventions, and the application of the results of such modelling exercises to public health policymaking. Methods: In conjunction with policymakers, existing public health models were adapted and used for simulating the effects of risk factor interventions on CHD in the England & Wales population. These models were evaluated in terms of the limitations of the input data, the assumptions underlying the methodology of the models, and problems in translating interventions to the simulation environment. Results: The simulation of CHD risk factor interventions using the Prevent and POHEM models demonstrated how public health models can be used with policy makers to estimate the future development of the health of populations; to evaluate alternative routes to achieving health goals; to demonstrate the effect of targeting health interventions at different sections of a population; to investigate the relationship between risk factors and their linked diseases; and for demonstrating the possible effect of health interventions to health practitioners. Conclusions: Public health models can be used as policy tools, although ultimately they may only inform policy, and not drive it, due to other factors which can influence the policy agenda. Such models are complex instruments that require a long term commitment in terms of funding, and they need to be developed by multidisciplinary teams, whose expertise cover the areas of computing, epidemiology and health policy, but most importantly policymakers should be involved with their development and use. Although public health models may never be validated in terms of a "gold standard", they can be used as policy tools as long as one is aware that they are unverified and that they yield results of a hypothetical nature.