UK general population utility values for the SIDECAR-D instrument measuring the impact of caring for people with dementia

Objectives: Dementia affects many people, with numbers expected to grow as populations age. Many people with dementia receive informal/family/unpaid care, e.g. from a spouse or child, which may impact carer quality of life. Measuring the effectiveness of health/social care interventions for carers requires a value measure of the quality of life impact of caring. This motivated development of the ‘Scale measuring the Impact of DEmentia on CARers’-D (SIDECAR-D) instrument. This study aimed to obtain general population values for SIDECAR-D to aid incorporating the impact of caring in economic evaluation.

Methods: Members of the UK general public completed a best-worst scaling object case survey, which included the 18 SIDECAR-D items and five EQ-5D-3L level 3 descriptions. Responses were analysed using scale-adjusted finite mixture models. Relative importance scores (RIS) for the 18 SIDECAR-D items formed the ‘SIDECAR-D relative scale’ measuring the relative impact of caring. The ‘SIDECAR-D tariff’, on the full health=1, dead=0 scale was derived by rescaling EQ-5D-3L and SIDECAR-D RIS so EQ-5D-3L RIS equalled anchored valuations of the EQ-5D-3L pits state from a visual analogue scale task.

Results: 510 respondents completed the survey. The model had two parameter and three scale classes. Additive utility decrements of SIDECAR-D items ranged from -0.05 to -0.162. Utility scores range from 0.95 for someone affirming one item to -0.297 for someone affirming all 18.

Conclusions: SIDECAR-D is a needs-based scale of the impact on quality of life of caring for someone with dementia, with a valuation tariff to support its use in economic evaluation.