[Health services Research Faces New Challenges: Consequences for Definition and Concept]

In Germany, Health Services Research (HSR) is undergoing rapid and impressive development. Starting from the translation of methods in individual health care (efficacy-effectiveness gap) and the social-scientific description as well as analysis of health care structures and processes, now it is the implementation of complex interventions on the organizational and system level that is the center of interest. This development is mainly triggered by the establishment of the so-called innovation funds by means of legislation in 2015, which has the task to evaluate structural changes and reforms in outpatient and integrated health care. Moreover, benefit and improvement at patient and population level is getting attention. Against this background, in this paper the current definition of HSR is modified so that the term "intervention" is extended to include organizational and system interventions, the focus on population is added to the patient perspective, and the orientation to appropriateness of care and improvement is integrated. Parallel to this, the theoretical throughput model as established by Pfaff in 2003 is updated, including 4 aspects: (1) the input factors of first order (resources of stakeholders) are expanded by complex interventions and active context as input factors of second order, (2) both undergoing modulation during the following throughput, (3) the final outcome is expanded by the population perspective, and (4) feedback loops from output and outcome to input and throughput are established. The "double complexity" of intervention and context as well as their interaction during throughput is the central and most important issue, because the interventions are highly context-sensitive and the complex context is most potent and poorly anticipated at the same time. Improvement science and implementation research represent fields of research from the perspective of improvement and the translation of knowledge and change of attitude, respectively, which are of great importance for HSR. Insofar as HSR is dealing with improvement and translation of complex interventions, the health care politics constitute an important transfer factor itself. Considering that, in the present situation, the political level represents both the main sponsor and the main demander of HSR results, improving methodological standards and further expansion of research structures of HSR are urgently needed.