How people live well with a diagnosis of dementia is of increasing interest to clinicians and researchers and quality of life is now a widely accepted central outcome in psychosocial research. However, quality of life is one of the few positive concepts to be measured for this population and there is still an overriding focus on negative behavioural and psychological symptoms including depression and agitation. We believe that, whilst these measures have contributed to a wealth of understanding, a more balanced view of wellbeing is needed, where measures of the strengths or capabilities that people with dementia retain are routinely included in research.

During a PhD project from 2014 – 2017, we developed two such outcome measures: the Positive Psychology Outcome Measure (PPOM) that assessed hope and resilience and the Engagement and Independence in Dementia Questionnaire (EID-Q) that assessed levels of social engagement and subjective independence.

In addition to developing these measures, we elected to psychometrically assess the CASP-19 for older adults with dementia. This was based on its theoretical underpinning as a measure of the positive dimensions of ageing and its strong psychometric properties for older adults documented in a systematic review we performed previously.

From 2016 – 2017, we recruited 225 people with dementia (59 – 99 years old) across the UK and asked them to complete five outcome measures: the CASP-19, PPOM, EID-Q, Quality of Life in Alzheimer’s Disease (QoL-AD) and the Geriatric Depression Scale Short Form (GDS-15). We asked 48 people to complete the measures again, with a one-week period to assess whether the measures were stable over time.

Our analysis of the CASP-19 documented strong psychometric properties, with acceptable levels of internal consistency and no floor or ceiling effects apparent. We also documented that the CASP-19 showed good consistency over the test and retest period. Our results suggested that the CASP-19 has important implications for wellbeing for people with dementia as those scoring above 10 on the GDS-15, and therefore likely to be experiencing clinically relevant depressive symptomology, were more likely to score lower on the CASP-19 and vice versa. We also found strong positive correlations between the CASP-19, QoL-AD, PPOM and EID-Q, suggesting that these positive concepts are also related.

However, a factor analysis indicated that the 19-item CASP measure may not be the most appropriate for people with dementia. To establish which factor structure was superior, a series of confirmatory factor analyses (CFAs) were performed using structures evaluated in previous studies of the CASP-19. We concluded that a 12-item CASP, combing the control and autonomy subscale was the most robust model.

Our research suggests that the CASP-12 is a psychometrically sound measure of wellbeing for older adults with dementia and can be used in further research for this population. Further large-scale research conducted as part of the Promoting Independence in Dementia (PRIDE) programme will determine whether the CASP-12 can capture responsiveness to interventions; a key component of psychometric analysis.

Guest blog: Dr Charlotte R. Stoner, Research Department of Clinical, Educational and Health Psychology, University College London (UCL).

Stoner, C. R., Orrell, M. & Spector, A. (2018). The psychometric properties of the Control, Autonomy, Self-realisation and Pleasure Scale (CASP-19) for older adults with dementia. Aging & Mental Health, Jan12, 1-7.  https://www.tandfonline.com/doi/abs/10.1080/13607863.2018.1428940?journalCode=camh20