Residents co-shaping urban NCD prevention: a citizen science process evaluation from HORUS Rijeka

Background

HORUS is a Horizon Europe project (GA No. 101136516) addressing non-communicable disease (NCD) risk behaviors in vulnerable urban populations through behavior change interventions supported by motivational interviewing and the Wakamola digital platform. A citizen science approach embedded residents as collaborators in intervention design, implementation, and evaluation. This study reports early process evaluation findings from the Rijeka pilot.

Methods

Guided by realist evaluation, we conducted Context-Mechanism-Outcome focus groups with residents and stakeholders in Rijeka, Croatia, at baseline (July 2025) and mid-intervention (March 2026); a post-intervention round is forthcoming. Baseline groups included 6 residents and 6 stakeholders; mid-intervention groups 9 residents and 4 stakeholders. Within the citizen science framework, participants validated interim findings and proposed adaptations to intervention delivery. Discussions examined facilitators, barriers, relevance, and sustainability.

Results

At baseline, participants identified green and public spaces, trust in professionals, and awareness of the need for change as conditions for healthier lifestyles. Mid-intervention findings showed that group-based activities, social support, and adaptation to needs increased engagement, community belonging, and uptake of healthy behaviors, particularly physical activity. Wakamola was perceived as supportive, but battery drain and poorly timed notifications reduced usability. Persistent barriers included stigma, low motivation, weak community leadership, and difficulty sustaining change.

Conclusions

Embedding citizen science within realist process evaluation enabled residents to co-shape an urban NCD-prevention intervention while generating actionable implementation evidence. Combining environmental opportunities with trusted communication and community support proved critical for engagement. Post-intervention data will complete the evaluation.

Key messages

• Citizen science and realist evaluation can be combined so that residents co-produce implementation evidence, not just provide data.

• Urban NCD-prevention interventions for vulnerable adults require sustained community leadership and stigma reduction alongside accessible group activities—without these, engagement gains may not hold.