Evaluating Health Care using System Dynamics Modelling – a Case Study in Schizophrenia

Abstract

AIM: To demonstrate based on a schizophrenia case study model that System Dynamics Modelling (SDM), a set of conceptual tools that help understanding the structure and dynamics of complex systems, can be a useful method in the field of health care evaluation, specifically to assess cost of illness and budget impact of complex diseases. METHODS: Using the specific Vensim DSS and Venapp software tools, a case study model was programmed, simulating schizophrenia costs in Germany up to the year 2050. Fixed model input was the age structure of the German population, the suicidal rate for the general population and for people diagnosed with schizophrenia, the general death rate and the proportion of suicides and schizophrenia prevalence and incidence. Subsystems of the model were: patient stocks and flows, medication cost, treatment cost, other relevant cost, occupational disability cost, early retirement cost, total schizophrenia cost, age distribution and auxiliary calculations. RESULTS: The case study schizophrenia SDM model allows analyzing the distribution of schizophrenia costs in the German health systems and demonstrates how the cost distribution changes with changing conditions (e. g. reduced relapse rate with the spread of more efficient medication). For the base case scenario - at the beginning of the model in the year 2000 - early retirement cost accounted for almost 50 % of the monthly total costs of schizophrenia of 474 180 000 €, followed by hospital costs, costs of occupational disability, and costs of non-medical complementary offerings. Indirect costs were much more important than direct costs. Costs of schizophrenia reached a peak around the year 2010 and decreased thereafter. With an increasing percentage of patients taking atypicals overall costs were decreasing. CONCLUSIONS: This paper supports system dynamics modelling as an alternative, flexible and user friendly modelling technique for application in health care evaluation.