Hypotheses to be worked out: Research methods like co-creation and process evaluation are methods that could promote the sustainability and the scalability of complex interventions.

Original research to be performed to address these hypotheses: For this PhD thesis, material and tools from two studies (COHESION and SALT) have been used in addition to a scoping review to map the research on process evaluation of complex interventions. The first and second articles of the current PhD thesis used the COHESION project to explain the steps followed for conducting a co-creation process and show lessons learned from this process. COHESION was conducted in Mozambique, Nepal and Peru. It included three formative studies (a policy analysis, health system assessment, and a community perception study), and following this research, a co-creation process was developed in three countries. The hypothesis of this study was that sustainable, gender and context appropriate interventions could be developed and integrated into primary healthcare responses through a clear understanding of barriers and enablers for diagnosis, management and care of NCDs and NTDs. The third and fourth article are the protocol and results of a scoping review which aimed to map out the use of process evaluation in complex interventions for NCDs and NTDs to identify gaps in the design and conduct, as well as strengths, limitations and implications, of this type of research in LMICs. Six databases were searched focused on studies published since 2008. The fifth article used data from the SALT project to conduct a process evaluation using the Medical Research Council framework. The SALT project was a population-wide implementation of a potassium-enriched salt substitute (75% NaCl and 25% KCl) to reduce blood pressure. A stepped-wedge, cluster randomized controlled trial was conducted in northern Peru, during the study six participating villages crossed over every 5 months from the control to the intervention phase. The intervention consisted in the introduction of a salt substitute using a social marketing campaign. Other elements of the intervention were a little spoon to incorporate the right measure of salt to the food and the “Amigas de Liz”, a group of women from the community that support the activities of the project. A qualitative study was conducted and data was collected from interviews from four out of the six villages. This data was used for this PhD thesis.

The five articles for this PhD thesis are used to show the potential of co-creation and process evaluation to promote sustainability and scalability of complex interventions.

Conclusions: This PhD contributes to highlight the role of two methods, co-creation and process evaluation, and their potential to promote sustainability and scalability of complex interventions. The strategic partnership built during co-creation could help to increase commitment with the implementation of the intervention and promote buy-in to promote sustainability. As for the role of process evaluation in terms of scalability, this allows for the identification of barriers and facilitators to implement an intervention that is related to certain contexts.