The application of interrupted time series designs for the evaluation of public health interventions

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What is the context of the research?Public health interventions (such as smoking legislation, health promotion programmes and health service changes) are generally applied to whole populations rather than individuals. Often, this means that traditional methods for evaluating whether an intervention works, such as a clinical trial for a new drug, cannot be applied. This results in a lack of knowledge about which public health interventions are most effective at improving health, resulting in inappropriate resource allocation with good interventions not being implemented and poor interventions being continued. One powerful method to evaluate interventions, which is frequently used in other fields such as economics, policy research and education research, but less commonly in health research, is interrupted time series (ITS) analysis. The basic principle is to compare the outcome of interest over time before and after an intervention whilst taking into account any underlying trends. Further development of this method in the context of public health will enable more robust evaluation of complex public health interventions.To which disease(s)/ condition(s), if any, is the research relevant?This research is relevant to the evaluation of all population level health interventions as well as some individual level health interventions which are not amenable to clinical trials.What is the research trying to achieve?This project aims to export and develop the ITS technique as a robust method to evaluate the effectiveness of public health interventions, implement the method in the evaluation of real life public health interventions and develop comprehensive guidelines on the appropriate usage of ITS methods in this field.Why is this important?This research will help us to accurately evaluate population level health interventions that would otherwise be difficult to evaluate. This is important for ensuring that the highest quality interventions which lead to the greatest health gains are implemented in practice.Who is carrying out the research?Dr James Lopez Bernal (Academic Clinical Fellow in Public Health) will be conducting this research for his PhD at the London School of Hygiene and Tropical Medicine. He will be supervised by Professor Steven Cummins (Professor of Population Health) who is an expert in the evaluation of public health interventions, and Dr Antionio Gasparrini (Lecturer in Biostatistics and Epidemiology) whose main research focus lies in time series analysis. The research will also involve collaboration with the Department of Population Medicine at Harvard University.How is the research being conducted?1) Existing knowledge on ITS methods from other disciplines will be collated and reviewed in order to understand where methods may be directly applicable to public health interventions and where there may be differences. Published ITS studies of public health interventions will then be reviewed in order to evaluate specific designs and analytical methods used and any methodological issues arising from them.2) At least two case studies will be conducted in which an ITS design will be used to evaluate the effectiveness of real life public health interventions, including:- Evaluation of the effect of a workplace health and wellbeing programme on ill health among employees.- Evaluation of the effect of the move to GP led commissioning of services in the NHS on referrals to specialist hospital care.3) Issues identified during the earlier stages of the project will be addressed by developing techniques to improve the robustness and accuracy of the ITS method and testing these on the case studies.4) The knowledge and experience gained during this research will be used to develop guidelines on the appropriate use of ITS designs for the evaluation of public health interventions.