Implementation of Combined Exercise, Fruit Intake, and Vitamin Supplementation Interventions to Prevent Frailty in Older Adults: A RE-AIM QuEST Evaluation

Background/Objectives: Accelerating population ageing has made community-based frailty prevention among older adults an important public health priority. Guided by the Reach, Effectiveness, Adoption, Implementation, and Maintenance Qualitative Evaluation for Systematic Translation (RE-AIM QuEST) framework, this mixed-methods study assessed the implementation outcomes and contextual factors of the multi-component Exercise, Fruit intake and Vitamin Supplementation (EFVF) program and identified factors relevant to its sustainability and potential adaptation to other settings. Methods: This implementation evaluation was embedded within a cluster-randomized controlled trial (ClinicalTrials.gov Identifier: NCT06225271) conducted across 14 community clusters in Wuzhong District, Suzhou, China, from March 2024 to April 2025. Quantitative data from participation records, implementation supervision records, and post-intervention follow-up questionnaires were combined with qualitative data from semi-structured interviews with 17 stakeholders, including 3 CDC administrators and 14 frontline primary care providers. Qualitative data were analyzed using a hybrid framework-guided inductive–deductive approach. Quantitative and qualitative findings were analyzed separately and integrated within the RE-AIM QuEST dimensions at the interpretation stage. Results: Of the 1380 eligible older adults in the intervention clusters, 475 (34.42%) initiated the EFVF program. Compared with 2248 eligible non-participants, participants showed similar sex distributions (p = 0.880) but differed significantly in age (p < 0.001), educational level (p = 0.002), and marital status (p < 0.001). Material incentives, health-seeking needs, community trust, and accessible venues facilitated participation, whereas agricultural work, family responsibilities, limited health literacy, and geographic barriers constrained Reach. Frontline providers perceived improvements in health awareness, dietary practices, exercise behaviors, and social interaction, while also reporting variation in participant responsiveness and limited maintenance of some behaviors after structured support ended. All seven intervention community health centers adopted the program, and 34 of 75 eligible frontline providers participated in delivery (45.33%). All 168 directly observed site-sessions met the prespecified core fidelity criteria, and 393 participants (82.74%) completed both intervention months. At follow-up, provider willingness for continued delivery varied, with 21.43% expressing unconditional willingness to continue the program. Conclusions: The EFVF program was implemented with high fidelity under trial-supported community primary care conditions, while frontline workload, behavioral maintenance, and organizational support remained important implementation considerations. These findings support feasibility under the study conditions but do not establish routine-care feasibility or scalability to other settings. Future adaptation should consider local population characteristics, staffing and workflow capacity, flexible delivery arrangements, and sustained organizational support. Multi-site pragmatic evaluation, including implementation cost assessment and longer-term maintenance, is needed before broader implementation can be established.