Quality of life in indigenous and non-indigenous older adults: assessing the CASP-12 factor structure and identifying a brief CASP-3.

PURPOSE: We assessed whether the original three-factor structure of the older adult CASP-12 Quality of Life (QOL) scale was stable for both indigenous and non-indigenous older adult populations in the same non-European country (i.e. New Zealand). METHOD: A total of 3076 New Zealanders aged 50-84 (Maori = 1,130; non-Maori sample = 1,946) completed a postal survey for the first data collection wave of the New Zealand Longitudinal Study of Ageing in 2010. The survey included the CASP-12, a chronic health conditions checklist, CES-D-10, de Jong Gierveld loneliness scale, and the WHOQOL single-item QOL indicator. RESULTS: Exploratory factor analysis revealed that the CASP-12 responses resulted in a revised two-factor structure for both Maori and non-Maori we called the NZCASP-11, which included a new three-item global indicator of QOL (CASP-3) that consistently cross-loaded on both factors. Confirmatory factor analysis supported the NZCASP-11 factor structure over the original CASP-12 model, and further assessment validated both the utility of the NZCASP-11 as an indicator of QOL in New Zealand and illustrated the utility of the CASP-3 as a brief screen for global QOL. CONCLUSION: While CASP items coalesce to provide a robust QOL indicator of indigenous and non-indigenous QOL in a single-country setting, the actual factor structure underpinning this CASP indicator (i.e. the NZCASP-11) is not entirely reflective of that found in the United Kingdom. Furthermore, we revealed that three CASP items (i.e. the CASP-3) may reflect a stable brief indicator of QOL applicable for assessing QOL across cultures within a single setting.