The Development and Validation of the Dementia Quality of Life Scale for Older Family Carers (DQOL-OC)

Abstract

Background: Family carers are considered to be the most important resource available to support people with dementia. The number of older people who are carers is increasing in the United Kingdom, and little is known about how caregiving affects their quality of life (QoL). The World Health Organization has established the importance of measuring individuals’ QoL and of developing and using age-specific QoL tools. However, to date no dementia- and age-specific QoL scale has been developed for use with older family carers. Aim: This PhD study aimed to develop and evaluate the psychometric properties of the ‘Dementia Quality of Life Scale for Older Family Carers’ (DQoL-OC), a dementia- and age-specific scale for the evaluation of QoL of older family carers. This tool might provide more robust QoL outcomes than scales currently being used with this particular population, helping to improve the quality of the evidence that results from studies and interventions aimed at evaluating and enhancing the QoL of these individuals. Methods: This is a sequential exploratory mixed-methods research. The DQoL-OC items were identified in four focus groups with 19 older family carers in Nottinghamshire. Data were transcribed verbatim and analysed by two researchers independently, using Interpretative Phenomenological Analysis. Inter-coder reliability was established using the Cohen’s kappa coefficient. A set of 89 items assessed using a five-point rating scale was generated and evaluated for content and face validity by a panel of six experts. The modified version of the DQoL-OC containing 100 items was then tested with a non-probabilistic sample of 182 older family carers in the UK who were providing care at home for family members with dementia. A battery of additional scales was administered to establish convergent construct validity: the Satisfaction with Life Scale; the WHOQOL-AGE QoL Scale; Perceived Health Status Visual Analogue Scale; and Overall Perceived Health-Related Quality of Life Visual Analogue Scale. The QoL model was identified using Exploratory Factor Analysis. Eighteen participants took part in the test-retest reliability, and the two measurement sets were correlated using Intraclass Correlation. Cronbach’s alpha was used to measure internal consistency reliability. The Pearson coefficient was used to provide evidence of convergent construct validity and the Spearman’s rho coefficient was used to correlate the DQoL-OC with other sociodemographic and caregiving variables. Results: Thirty-three themes emerged from focus groups and were collated into three superordinate themes: aspects of care and caregiving; feelings and concerns; and satisfaction with life and with caregiving. Very good inter-coder reliability was established (r=0.839). The psychometric study demonstrated that a one-factor solution containing 22 items best represented the new QoL model. Excellent test retest reliability (lower bound r=0.835; <0.0001) and internal consistency (α=0.936) scores were obtained. Convergent construct validity was established for all tested scales (<0.0001). Significantly lower levels of QoL were found in female older carers, those who perceived their relatives with dementia as being at the earlier stages of the disease and with unstable dementia symptoms, those providing care more hours per day and more days per week, and those in younger-old age. Conclusion: This study allowed the exploration of a broad range of aspects that are of particular importance for the QoL of older family carers of people with dementia. The DQoL-OC was considered by participants to be a relevant and useful measure of QoL. DQoL-OC is a valid and reliable 22-item tool assessed using 1 to 5 rating scales, which may be useful in clinical practice and in research in order to improve the QoL of older family carers of people with dementia. These findings will inform future health and social care practice with regards to improving life quality for this overlooked sector of the population