Debate on the paper by Diez Roux

Abstract

Systems approaches could provide a better understanding of urban health determinants and inform interventions. What are the next steps in delivering this promise?Diez Roux presents in this Supplement of Cadernos de Saúde Pública a clear argument for why systems theory should be instrumental for understanding the root causes of urban health and for tackling ill health and inequalities in cities. I am persuaded by the ways in which systems theory can help transform research and action for urban health, as she proposes. She focuses particularly on the development of conceptual dynamic models of the processes leading to health in urban settings, drawing on inputs from researchers and stakeholders, which in turn draw on scientific knowledge and contextual/local factors, while mapping out expected feedback loops and dependencies. These conceptual models are essential for clarifying/generating hypotheses about linkages between health and the urban environment and for identifying potential interventions and their expected impacts on health.The second mechanism she proposes is simulation modelling of such relations to examine expected impacts from interventions, considering possible pathways and feedback loops. The creation of these "virtual worlds" is both attractive and tantalizing, in that the more complexity one adds to the model, the greater the possibilities of error and eventual misunderstanding of the systemic effects. This also raises a number of questions, including who sets the parameters, which aspects are included in the model and which are left out, various hierarchies, and how one considers conflicting interests in the absence of consensus. On the other hand there is an opportunity to learn from the experience in cities worldwide