Development and Cross-Sectional Validation of the Quality of Life and Function Five-Domain Scale (QFS-5) in Dementia-Free Community-Dwelling Older Adults

INTRODUCTION: Quality of life (QoL) captures objective life conditions, subjective wellbeing, and personal aspirations. Interest is growing in ability-based, patient-centered instruments, not confounded by health outcomes. The Quality of Life and Function Five Domain Scale (QFS-5) uses a multi-dimensional approach to measure QoL emphasizing abilities and life engagement. We describe the development and validation of the QFS-5 in a large sample of community-dwelling older adults. METHODS: The validation sample comprised 1610 participants aged ≥ 50 from the Canadian Platform for Research Online to Investigate Health, Quality of Life, Cognition, Behavior, Function, and Caregiving in Aging (CAN-PROTECT). Internal consistency was assessed using Cronbach's alpha and item-total correlations. Confirmatory factor analysis (CFA) evaluated domain structure. Criterion validity was tested through Pearson's correlation with the EuroQol-5D (EQ-5D). Convergent and discriminant validity were evaluated from associations with cognitive, mental health, and functional measures. Floor and ceiling effects were investigated. RESULTS: The QFS-5 demonstrated excellent internal consistency (α = 0.92); CFA supported the proposed domain structure with strong item loadings. Criterion validity was confirmed with correlation of -0.61 against the EQ-5D; higher symptom burden on related scales were associated with lower QFS-5 scores. Floor effects were minimal, while modest ceiling effects were observed in some domains. No significant floor or ceiling effects were found in participants with frailty. CONCLUSION: Validity and reliability are established for this ability-based QoL scale, within a sample of mostly cognitively unimpaired, community-dwelling older adults. The QFS-5 aligns with EQ-5D, demonstrating potential clinical and research utility to measure relevant patient-reported QoL outcomes.