Exploring differences and similarities of EQ-5D-3L, EQ-5D-5L and WHOQOL-OLD in recipients of aged care services in Germany

European countries more than ever face shifts towards aging societies with accompanying challenges for health and aged care services. Economic evaluation has mainly relied on health measures such as EQ-5D across populations and conditions. We want to know how well the EQ-5D performs in the target population to avoid bias to the disadvantage of older adults and care-dependents. Therefore, we aim to explore differences and similarities of EQ-5D-3L and EQ-5D-5L in comparison to the old-age specific WHOQOL-OLD instrument in a sample of older adults receiving aged care services. We collected data from n = 329 older adults (≥65 years) receiving aged care services in Germany; the majority was at least 80 years and had varying care needs. We assessed instruments' feasibility, test-retest reliability, instruments' association and sensitivity to known-group differences. In terms of feasibility and test-retest reliability both EQ-5D versions performed better than the WHOQOL-OLD. All measures differentiated well between groups based on aspects of general health and care levels. The analysis of relationship between measures indicated that EQ-5D and WHOQOL-OLD assess partially overlapping, but distinct constructs. We found no clear evidence of superiority of either EQ-5D version over the other. The EQ-5D-5L performed better in terms of test-retest reliability and stronger correlations with WHOQOL-OLD facets. We conclude that using the WHOQOL-OLD alongside EQ-5D in this sample added further information on different aspects of quality of life.