Companion Value Co-Creation and Well-Being in Older Adults with Chronic Illness: A Cross-Sectional Dyadic Study in Spain

<b>Background:</b> Companion participation in medical consultations can influence the well-being of older adults with chronic illness, yet the mechanisms underlying this effect remain unclear. This study aimed (1) to examine how companion-reported value co-creation (coproduction and value-in-use) relates to patient-reported multidimensional well-being (psychological, existential, social, and physical), and (2) to test whether these associations vary according to patient and companion characteristics. <b>Methods:</b> A cross-sectional dyadic study of 907 patient-companion pairs (N = 1814) was conducted in Spain prior to the COVID-19 pandemic. Companions completed the adapted Spanish Value Co-creation Scale, while patients completed the McGill Quality of Life Questionnaire-Revised (MQOL-R). Construct validity was confirmed via confirmatory factor analysis, and structural equation modeling tested hypothesized relationships using robust maximum-likelihood estimation. <b>Results:</b> The model showed good fit (χ²/df = 2.41, CFI = 0.96, RMSEA = 0.041). Companion coproduction was positively associated with patient psychological (β = 0.32), social (β = 0.27), and existential well-being (β = 0.29), but not physical well-being. Value-in-use showed small negative associations (β ≈ -0.10 to -0.15), which may reflect relational strain arising when companions' involvement is excessive or mismatched with patient needs. Coproduction effects were stronger among patients aged ≤75 years. <b>Conclusions:</b> Companion coproduction enhances key dimensions of patient well-being, highlighting its role as a relational resource in clinical practice. Conversely, higher companion value-in-use may signal potential relational strain. These pre-pandemic findings provide a baseline for post-COVID chronic care models that aim to actively involve companions and tailor support according to patient age.