¹Institute of Public Health, Medical Decision Making and Health Technology Assessment, Department of Public Health, Health Services Research and Health Technology Assessment, UMIT TIROL - University for Health Sciences and Technology, Hall in Tirol, Austria
²Centre for Public Health and Wellbeing, University of the West of England, Bristol, United Kingdom
³Institute for Global Health (ISGlobal), Barcelona Biomedical Research Park (PRBB) Doctor Aiguader, Barcelona, Spain
⁴Research Group On Methodology, Methods, Models and Outcomes of Health and Social Sciences (M3O), Faculty of Health Sciences and Welfare, Centre for Health and Social Care Research (CESS), University of Vic-Central University of Catalonia (UVic-UCC), Barcelona, Spain
⁵Institute for Research and Innovation in Life Sciences and Health in Central Catalonia (IRIS-CC), Vic, Spain
⁶Center for Health Decision Science, Departments of Epidemiology and Health Policy & Management, Harvard Chan School of Public Health, Boston, United States
⁷Institute for Technology Assessment and Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, United States
⁸Institute of Public Health, Medical Decision Making and HTA, Department of Public Health, Health Services Research and HTA, UMIT - University for Health Sciences, Medical Informatics and Technology, Hall in Tirol, Austria

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Objective: Loneliness adversely affects physical and mental well-being [1]. Nature-based social prescribing (NBSP) has emerged as strategy to mitigate loneliness. This study, framed within the RECETAS [2], [3], evaluates the broader impact of investing in NBSP considering the social, environmental, and economic impacts next to financial effects.

Methods: To conduct a Social Return on Investment (SROI) analysis using quantitative and qualitative data from our Barcelona's randomized controlled trial, an impact map was developed following key principles of SROI studies [4]. Using the RECETAS logic model [3], key stakeholders, intervention impacts and measurable outcomes were defined. In absence of Spanish financial proxies for changes in these outcomes, 2014 British Pounds values from the Social Value Bank (SVB) [5], were converted into Spanish Euros (EUR, 2023) using the Purchasing Power Parity and Consumer Price Index and transformed into three-month values to match the intervention period. Intervention costs for were identified to be valued upon completion of the trial. The SROI ratio will be calculated as total social value from all stakeholders divided by intervention costs.

Results: Key stakeholders identified include participants, care providers, voluntary and community sector organizations (VCSO), volunteers, and the national healthcare system (Sistema Nacional de Salud, SNS). Participants experience an improvement in loneliness and health-related quality of life (HRQoL). A reduction of more than two points on the De Jong-Gierveld Loneliness Scale is valued at EUR 515 ('Being a member of a social group') [5]. An improvement in HRQoL, with an increase of more than 0.1 in the health utility score based on the EQ-5D-5L, is valued at EUR 5,605 ('Good overall health') [5]. The SNS benefits from lower consumption of medical resources, measured by changes in physician visits, specialist consultations, and medication usage, valued using unit costs. The benefit of care providers, a reduced burden on the care system due improved population health, is considered in the outcome benefits for the SNS. VCSO benefit from participants increased engagement in social activities, valued at EUR 1,044 ('Feeling a sense of belonging to the neighborhood'). Increased life satisfaction due to volunteering, is valued at EUR 656 ('Regular volunteering’) per volunteer.

Intervention costs include personnel expenses, facilitator transport, materials, recruitment, training, and research-related costs, which would normally not be considered part of the intervention.

Discussion: External financial proxies from the SVB provide a useful reference for valuing non-market goods. However, these proxies are not tailored to the specific context and country of this study. No Spanish valuation source exists and it is unclear whether results are transferable to other countries, such as Germany. While startup and development costs may initially inflate the investment, long-term maintenance costs would be lower for wider implementation of the intervention affecting the accuracy and applicability of monetarized estimates and the SROI ratio.

Conclusion: The SROI analysis provides a comprehensive framework to quantify the social value of NBSP interventions once trial results are available. The SROI ratio quantifies the social value per Euro invested. Qualitative data through stakeholder engagement and RECETAS expert input will further enhance validity and impact.

The RECETAS project received funding from the European Union’s Horizon 2020 Research and Innovation program under grant agreement No 945095.

The authors declare that a positive ethics committee vote has been obtained.

References

[1] World Health Organization. Social isolation and loneliness among older people: advocacy brief. Geneva; 2021.
[2] Coll-Planas L, Carbo-Cardena A, Jansson A, Dostalova V, Bartova A, Rautiainen L, et al. Nature-based social interventions to address loneliness among vulnerable populations: a common study protocol for three related randomized controlled trials in Barcelona, Helsinki, and Prague within the RECETAS European project. BMC Public Health. 2024;24(1):172.
[3] Litt JS, Coll-Planas L, Sachs AL, Rochau U, Jansson A, Dostálová V, et al. Nature-based social interventions for people experiencing loneliness: the rationale and overview of the RECETAS project. Cities & Health. 2024:1-14.
[4] Nicholls J, Lawlor E, Neitzert E, Goodspeed T. A Guide to Social Return on Investment. Cabinet Office; 2012.
[5] Trotter L, Vine J, Leach M, Fujiwara D. Measuring the Social Impact of Community Investment: A Guide to using the Wellbeing Valuation Approach. HACT (Housing Associations' Charitable Trust); 2014.