A validation study of the CarerQol instrument in informal caregivers of people with dementia from eight European countries

In 2019, the number of people with dementia was estimated at 50 million worldwide, and every 3 s a new case of dementia occurred [1‐3]. The number of people with dementia therefore is increasing rapidly and will most likely more than triple by 2050 [3, 4]. Furthermore, dementia has a huge economic impact. The worldwide care costs of dementia in 2015 were estimated to be 818 billion dollars [1]. With no cure that can alter the course of this disorder or modifying treatment currently available, it is crucial that a caregiving context is created in which people with dementia are supported in their care needs.

Dementia is a chronic syndrome that progresses over time with corresponding increasing care demands [5, 6]. Most of this care is placed on the shoulders of family members of the person with dementia [7]. It was estimated that informal care has a three-to-one ratio with formal care in care provided/received [6, 8].

Informal care for people with dementia plays a crucial role in the total care for people with dementia and is relatively time intensive [5, 9, 10]. Without sufficient help, providing informal care to someone with dementia can turn into a full-time job [11] with significant influence on the well-being of the caregiver [12]. On the one hand, caring can be very gratifying and caregivers may experience positive utility from providing care [13, 14], but on the other hand, it can also be experienced as burdensome and overwhelming [15], potentially leading to physical, emotional and economic strain [3, 12]. Because the role of informal caregivers can be expected to remain indispensable in the foreseeable future, interventions aimed at supporting and strengthening caregivers of people with dementia are extremely important [5].

Most health care systems struggle with accommodating the rising demand for health and social care from a limited budget. Economic evaluation studies are increasingly used to inform decision-makers about which interventions to fund and not to fund [16]. Informal care can have a strong impact on the outcomes of these economic evaluations, but it is usually not considered [17]. In addition, studies that do consider informal care mostly focus on the costs of caregiving (the numerator in the cost-effectiveness ratio), which constitutes only partial information on the overall effects of providing care on informal caregivers. For a fair consideration of the full impact on caregivers in economic evaluation studies, it is important to assess the effect of providing informal care on the well-being of caregivers (the denominator in the cost-effectiveness ratio). The CarerQol (Care-Related Quality of Life) instrument was developed for this purpose [18].

The CarerQol instrument can be used in economic evaluations for two purposes. First, as primary outcome measure in evaluations of interventions aimed at informal caregivers. Secondly, as additional information in evaluations of health and social care interventions for people with dementia. Since its introduction in 2006 [18], the CarerQol has been validated in different populations and caregiving contexts such as family of caregivers of children with craniofacial malformations, parents of adults with Duchenne muscular dystrophy, caregivers of a child with autism spectrum disorder and caregiver outcomes in palliative care [19‐25]. Until now, the CarerQol has been used once in a population of informal caregivers for people with dementia [26]; however, it has never been validated in this population. Considering that the validity of an instrument may differ between settings, it is important that the CarerQol is also validated in the context of dementia. The aim of this paper was to investigate the convergent and clinical validity of the CarerQol in the context of informal caregivers for people with dementia, using cross-sectional baseline data from eight European countries collected within the Actifcare (Access to TImely Formal care) project [27].

The characteristics of our study sample are shown in Table 1. Caregivers had an average age of 66 years and were predominantly female (66%). They had an average of 12 years of education, 28% was employed and 63% was retired. The caregivers rated their health and well-being on average as reasonably good, with an EQ-5D health problems score of 7.9, an EQ-VAS score of 72, and an ICECAP-O score of 0.78. On average, care receivers were almost 12 years older than caregivers and 55% of care receivers were female. The average number of years of education was nearly 10, and almost all were retired (93%). Care receivers had an EQ-5D health problems score of 7.9, which was similar to the score of caregivers. For one out of five of the care receivers, their dementia was rated as ‘moderate or severe dementia’ (CDR > 1). Most care receivers had low to moderate problems with their mental health and were dependent on help because of their physical health. Less than 5% of care receivers stayed in a hospital during the past 30 days, 72% saw a healthcare professional at home once or more often, and 26% reported one or more home care visits by a healthcare professional. About 35% had no unmet care needs, a similar proportion had one or two unmet needs, and 28% had three or more unmet care needs.

The majority of caregivers (63%) provided informal care to their spouse or partner, and 71% shared a household with the care receiver. Mean caregiving time over the past 30 days was 6.0 h per day (95% confidence interval: 5.4 to 6.5 h), with about 29% providing 8 h of care per day or more. Approximately 13% of the caregiving time was spent on assisting with basic activities of daily living, 45% on assisting with instrumental activities of daily living, and 42% on supervising the person with dementia.

Regarding PT, 71% of caregivers indicated they would be able to carry on with their caregiving activities for at least 2 years if the care situation remained the same.

This study investigated the convergent and clinical validity of the CarerQol instrument as measure of the impact of caregiving for people with dementia on informal caregivers, using rich data from a multi-country sample. The correlations between the CarerQol-7D utility score and the CarerQol-VAS, PT, ICECAP-O utility score and EQ-5D health problems score of the caregiver had the expected direction and were statistically significant, but for some a lower strength was found compared to what was expected. Previous research using these data found a strong and positive correlation between the CarerQol-7D and the ICECAP-O [34], a measure of overall capability well-being; in this study we report the same coefficient (0.53). As expected, the positive (negative) dimensions of the CarerQol-7D were positively (negatively) correlated with the CarerQol-VAS, although some only weakly. These findings generally support the convergent validity of the CarerQol instrument in this sample. In addition, the CarerQol instrument was able to distinguish between subgroups defined by a number of relevant characteristics of caregivers, care receivers and the caregiving situation in the expected directions, more specifically, the age and health of caregivers, the CDR, visits to healthcare professionals and unmet care needs of care receivers, and caregiving time. This generally supports the clinical validity of the CarerQol instrument. We also hypothesized that there would be no significant differences in CarerQol scores between the participating countries, as there was no previous evidence suggesting this. Although the observed mean CarerQol-7D utility scores differed considerably between countries (Table 2), the multivariate analyses showed that these differences were most likely related to differences in the composition of the samples between the countries and reflect differences in healthcare systems. This confirms our hypothesis.

The convergent and validity results of this study among caregivers for people with dementia are generally in line with findings from previous CarerQol validation studies in other settings [18, 23, 24]. Although most of these studies focused on the CarerQol-VAS and CarerQol-7D dimensions instead of the CarerQol-7D utility score, as utility tariffs were not yet available when these studies were conducted, the results are comparable. Therefore, this study confirms that the CarerQol instrument may be a useful instrument to assess the impact of caregiving on the well-being of informal caregivers for use in economic evaluations of interventions for caregivers or care recipients [23].

Some limitations of this study need to be mentioned. First of all, UK value sets were used to compute utility scores for the CarerQol and the ICECAP-O for all countries included in the analysis, because at this time country-specific value sets were not available for these instruments for each of the countries included in this study. Using the same utility tariffs for all supports the comparability across countries; however, this obviously may limit the representativeness of these scores in the separate countries, as the relative value of dimensions and levels may differ from those in the UK. It would be helpful if country-specific value sets for the CarerQol and ICECAP-O were developed for more countries. Furthermore, in this study we used the capability well-being measure ICECAP-O for testing the convergent validity of the CarerQol. Ideally a carer-specific measure would have been used; however, at the time of development of the protocol of this study no alternative measures with utility weights were available. It is also important to note that the ICECAP-O was used for both people with dementia and their carers, where 43% of the caregivers were < 66 years old. However, the ICECAP-O was initially developed for people 65 years and older and it is not completely clear how valid this measure is in capturing the well-being of people below this range. Although the size of the overall sample is sufficient for the intended analyses, the sample sizes per country ranged between 41 and 74. This raises questions about the possibility to conduct country-level sub-group analyses. The sample consisted of people with relatively mild dementia and mostly low burden care situations. Although this arguably may be the most prevalent caregiving situation in the context of informal care for people with dementia in the community, this limits the generalizability of our findings to the wider population of caregivers for people with dementia. In addition, convenience sampling possibly has underrepresented highly burdened caregivers not able to participate in this study. Finally, although questionnaires were carefully back-translated and pilot-tested, most of the instruments were not validated in all the different countries. Therefore, our findings may be biased by cultural differences in the comprehensiveness of the various measures and the way participants interpreted and responded to these measures. Future research should focus on validating the instruments in all different countries and on cross-cultural validation.

One of the strengths of the current study is that, as compared to previous validation studies of the CarerQol instrument, we had a sizeable sample from different countries at our disposal. Secondly, the data contained a large variety of characteristics of caregivers, care receivers and caregiving situations relevant for this specific population. Finally, data were gathered on and from both caregiver and care receiver, using a detailed protocol and trained interviewers in all participating countries, which promoted the comprehensiveness and quality of the data available for this study. Nevertheless, future studies would benefit from a larger sample size (per country) and the availability of country-specific validated versions and value sets for the various measures of outcome. In addition, panel data would facilitate the investigation of causality in the relation between caregiver outcomes and characteristics of caregivers, care receivers and the caregiving situation. This would be important to improve the quality of the evidence in this area, which in turn would support the consideration of effects of interventions in health and social care for people with dementia on their informal caregivers. This research has shown that the impact on informal caregivers is related to the severity of dementia and the size of the caregiving task. This finding is relevant for future policy, given the current emphasis in many countries on promoting people with dementia to live at home longer. The growing number of people with dementia worldwide and the limited availability of informal caregivers emphasize the importance of adequate support for informal caregivers to assist them in their important caregiving tasks. Our findings suggest that special attention should be directed at caregivers of older age and who have health problems themselves, and more demanding care situations in terms of severity of the health problems and unmet care needs of the care receiver, and hours of caregiving required.

It is worth noting that there are many measures of caregiving effects available, with different properties and scopes of measurement and valuation. The CarerQol is a relatively short (i.e. seven items) and generic measure, whereas, for example, the recently introduced the SIDECAR (Scales measuring the Impact of DEmentia on CARers) [46] is a fairly elaborate (i.e. 39 items) and dementia-specific measure. Disease-specific measures generally have the advantage of capturing the effects on carers for patients in that particular population more precisely, while generic measures have the advantage that measurement of effects is the same and hence comparable across carer and patient populations, which facilitates development and evaluation of policies on a more general level. In addition, many measures focus only on the burden of caregiving, while for many carers there are also positive effects—such as the fulfilment item included in the CarerQol—that potentially make the overall caregiving experience less straining [18]. Finally, measures differ in how carers can report their experience (e.g. yes/no, agree/disagree, or different degrees/levels) and whether and how a sum-score is defined. For use in economic evaluations, it is preferable that utility weights are available to compute a (care-related) quality of life score.

Concluding, this study in a multi-country sample of informal caregivers for people with dementia confirms previous findings in other populations that the CarerQol instrument has satisfactory convergent and clinical validity in the population of informal caregivers for people with dementia. These findings support that the CarerQol instrument is potentially useful in economic evaluation studies, either as additional information in evaluations of interventions for people with dementia or as a primary outcome measure in evaluations of interventions for informal caregivers.