Discussion

To our knowledge, this is the first scoping review that provides evidence on the sustainability of HSS interventions targeting PHC settings. It also sheds light on the existing challenge to document the sustainability of externally funded HSS interventions. Over 20% of the studies in the full text review were excluded because, while they referred to or mentioned sustainability, they did not measure it. These studies discussed factors assumed to facilitate reaching sustainability in the future but did not present an actual assessment of it. While previous studies recommended that sustainability should be specified conceptually and operationally by aligning with existing frameworks,4 7 10 only half of the studies included in the review explicitly mentioned a sustainability definition. Choosing an appropriate definition is imperative as it dictates how sustainability will be investigated.10 Different definitions lead to distinct research approaches. For instance, definitions focused on preserving the original intervention may measure sustainability based on programme fidelity and long-term implementation. In contrast, definitions from a complex systems perspective emphasise how interventions adapt to and interact with the context over time, influencing the way sustainability is assessed in relation to environmental and contextual factors. Thus, the chosen definition shapes both the methods and conclusions of sustainability research.10 Additionally, although the methodological guidance for conducting sustainability research has increased over the recent years, there remains a lack of standardised tools facilitating HSS intervention sustainability assessments.

According to the reviewed evidence, the sustainability assessment approaches and timing are shifting. In the past, sustainability was believed to be best measured at least 1–2 years after the implementation of initiatives.4 Recently, the idea of sustainability being a process that requires exploration throughout implementation has strongly emerged. It has also been recommended that sustainability should be measured at multiple time points.9 Most of the studies identified by our review assessed sustainability retrospectively, but some looked at sustainability prospectively, while implementation was still ongoing. The majority of the former provided their own operational definition and created a scale to measure at what level the sustainability was achieved.21 22 26 In these studies, partial sustainability was more common than full continuation of programme or benefits, consistent with previous findings.10 The latter studies did not claim to have reached sustainability while project transfer activities to government ownership were ongoing, setting the initiation steps for sustainability. These studies emphasised the need for future sustainability evaluations.23 28 The results from these prospective studies corroborate those of Lennox et al, which stated that such studies focus on building an initiative into an organisation, aligning it to stakeholder and setting needs, and getting stakeholders on board.31

A key finding of our review was that both institutionalisation and continued programme activities emerged as the most common sustainability outcomes for HSS interventions. The sustainability literature refers to institutionalisation as continued programme implementation, but Shelton and colleagues provided a separate definition for institutionalisation, establishing the difference between the two outcomes.9 Specifically, institutionalisation is conceptualised as maintaining organisational practices, procedures and policies started during implementation. The findings from our review seem to support this separation, as some studies appear to refer to institutionalisation, some to continued programme implementation and some to both. Institutionalisation reflects the structural integration of an intervention into the system, ensuring its long-term continuation in a static manner, whereas continued programme activities address sustainability in the context of change over time, allowing for adaptability and capacity building to respond to new evidence, policies or other influencing factors. The distinction between the two outcomes stands in the flexibility to adapt the intervention and its components to evolving circumstances. Institutionalisation in our review was due to the nature of HSS interventions, which focus on systemic improvements, which on their own require lasting system changes in organisational practices, procedures or policies. Thus, the intent to institutionalise lies at the core of such interventions. As for continued programme activities, this outcome has previously been found to be common in studies overseeing sustainability of healthcare initiatives.31

The most important finding of our review was that the sustainability drivers of HSS interventions were mostly related to processes, inner context, intervention characteristics and outer context. While interventions targeted the national PHC system, the setting varied, which may explain this distribution. Some interventions focused on the entire PHC system at national level, while others focused on subnational areas or even the facility or community health services level. This finding corroborates previous research indicating that sustainability factors vary by settings.9 11 12 Further, process-related findings capture the importance of stakeholder engagement, which ensures the relevance of the intervention in the context of local needs and priorities, as well as long-term support. This finding is supported by previous research findings in low- and middle-income countries,9 32 33 where seven of the eight included studies were conducted. Further, the most cited inner context factors were the presence and support of competent leadership, presence of champions and programme integration. While the first two have a wide recognition, programme integration is an emerging imperative to reduce fragmentation and ensure the intervention becomes a part of the system. In terms of intervention characteristics, not surprisingly, the intervention’s ability to adapt and fit with the population and the context is the most commonly reported influencing factor. Complementing the ISF, interaction displayed between the processes and intervention characteristics—that is, stakeholder engagement and intervention fit and adaptability to the context—was also highlighted, confirming the dynamic nature of the systems where interventions take place.5 10

The review identified a broad spectrum of barriers to sustainability. The most prominent one was related to funding (either external or internal). Lack of adequate financial resources, lack of locally driven financial investment, presence of fiscal stress and inadequate uptake of financial responsibilities by governments were identified as barriers to the sustainability of HSS interventions. Akeju et al highlighted the importance of preparing the systems to assume financial responsibility before the external funding period elapses and recommended exit strategy discussions to take place during project review meetings.21 Notably, seven of the eight studies included in this review were from low- and middle-income countries. This comes as no surprise, considering that one of our exclusion criteria ruled out studies with system-driven changes, where HSS interventions were initiated and received funding from state institutions, reflecting the government commitment to the interventions. Nearly all screened studies from high-income countries described system-driven interventions, leading to their exclusion. Another important barrier cited was sociopolitical context, mainly due to strong linear and hierarchical structures, low level of decentralisation, devolution and political interference, and political instability. This emphasises yet again the value of obtaining and nurturing long-term leadership support as well as engagement of stakeholders from the inception in order to align the interventions with the vision and the needs of the particular system. Another highly cited barrier was staffing issues, reported as shortages, turnover, lack of assessment of human resource needs and non-payment of staff.

A factor that was less represented than expected in our findings was programme evaluation. In fact, lack of programme evaluation was reported as one of the hindering factors solely by Israr et al, the only study in our review that did not reach institutionalisation.25 However, the majority of the studies included in the review had conducted monitoring and evaluation of the programme during implementation or at its end, which aligns with the growing emphasis on rigorous evaluation efforts to strengthen HSS interventions.34 It seems that there is recognition of the importance of evaluation in adapting and improving interventions over time, ultimately contributing to long-term success. This aligns with findings from studies across various contexts.9 We speculate that the studies included in our review simply failed to report evaluation as an influencing factor for sustainability.

Additional relevant studies were identified during the review, which were however excluded due to not satisfying all of the inclusion criteria. These studies described successful HS reforms around PHC restructuring, modelling or strengthening in Costa Rica, Bosnia and Herzegovina and the Kyrgyz Republic.35–37 They were excluded because, despite receiving considerable external support, the primary drivers of change and implementation were domestic, namely the Ministry of Health and Social Security Administration in Costa Rica, the government in Bosnia and Herzegovina and the Ministry of Health in the Kyrgyz Republic. Beyond being system driven, these studies shared other commonalities which differentiated them from the included studies, such as receiving extensive financial support from international organisations including the World Bank, WHO and the International Monetary Fund, and the long interval until reform outcomes were evaluated (between 5 and 25 years). All three studies sustained the reform components.

These studies further support Schreier’s hypothesis that sustainable broad-scale system change interventions require continued financial support for a long period of time instead of the usual grant period of 3–5 years.12 Further, the literature suggests that sustainability should be assessed at least 1 year after the implementation of an intervention has been completed,4 6 10 while such broad systemic changes might require a longer time horizon to become entrenched. Conducting longer term sustainability assessments ensures that the reforms have been fully institutionalised and provides a comprehensive picture of whether practices and policies have been maintained and/or adapted.

Going forward, externally funded HSS interventions should consider planning for sustainability assessments, by including a theoretical or operational definition of sustainability, choosing a method, an approach and a timeframe to measure the sustainability outcome. This will help address the current literature gap by providing stronger evidence on how to implement HSS interventions with a long-lasting effect.