OBJECTIVES: The Adult Social Care Outcomes Toolkit for Carers (ASCOT-Carer) is a preference-based measure (PBM) for assessing caregiver’s social care-related quality of life (SCRQoL). However, its validity remains inadequately established. This study explores the associations between ASCOT-Carer and EQ-5D-5L as Health-Related Quality of Life (HRQoL) on caregiver burden.

METHODS: A web-based survey was conducted with 705 caregivers of patients with Alzheimer’s disease in Japan. The criterion-related validity of ASCOT-Carer, EQ-5D-5L, and the short version of the Japanese Zarit Caregiver Burden Interview (J-ZBI-8) were evaluated through correlation analysis. Additionally, exploratory factor analysis (EFA) with oblimin rotation was performed on all items from these scales to analyze their inter-factorial correlations.

RESULTS: Moderate correlations existed between ASCOT-Carer and EQ-5D-5L and between ASCOT-Carer and J-ZBI-8, with correlation coefficients (r) of 0.46 and −0.47, respectively. The relationship between EQ-5D-5L and J-ZBI-8 was weak (r = −0.254). EFA yielded a 7-factor model based on Bayesian Information Criterion, where items within each scale did not merge with items from other scales. The resulting 7-factor model of the EFA is outlined as follows: Factors 1, 4, and 5 consisted of items from the J-ZBI-8 scale, focusing on aspects related to roles, emotions, and four other factors. Factors 3 and 6 comprised items from the EQ-5D-5L scale, centering on pain and anxiety, alongside three additional items. Factors 2 and 7 were composed of items from the ASCOT-Carer scale, specifically addressing control over daily life, along with six other items. Inter-factor correlations were moderate for factors related to ASCOT-Carer and J-ZBI-8, and weak for factors related to EQ-5D-5L and J-ZBI-8.

CONCLUSIONS: ASCOT-Carer, EQ-5D-5L, and J_ZBI_8 effectively captured unique dimensions of SCRQoL, HRQoL, and caregiver burden, respectively. ASCOT-Carer seems more effective than EQ-5D-5L for assessing caregivers' QoL and holds promise as a PBM, with potential use in health economic evaluations.