Impact of Alzheimer’s Disease on Caregiver Questionnaire: internal consistency, convergent validity, and test-retest reliability of a new measure for assessing caregiver burden

Abstract

BackgroundThere is a lack of validated instruments to measure the level of burden of Alzheimer’s disease (AD) on caregivers. The Impact of Alzheimer’s Disease on Caregiver Questionnaire (IADCQ) is a 12-item instrument with a seven-day recall period that measures AD caregiver’s burden across emotional, physical, social, financial, sleep, and time aspects. Primary objectives of this study were to evaluate psychometric properties of IADCQ administered on the Web and to determine most appropriate scoring algorithm.MethodsA national sample of 200 unpaid AD caregivers participated in this study by completing the Web-based version of IADCQ and Short Form-12 Health Survey Version 2 (SF-12v2™). The SF-12v2 was used to measure convergent validity of IADCQ scores and to provide an understanding of the overall health-related quality of life of sampled AD caregivers.The IADCQ survey was also completed four weeks later by a randomly selected subgroup of 50 participants to assess test-retest reliability. Confirmatory factor analysis (CFA) was implemented to test the dimensionality of the IADCQ items. Classical item-level and scale-level psychometric analyses were conducted to estimate psychometric characteristics of the instrument. Test-retest reliability was performed to evaluate the instrument’s stability and consistency over time.ResultsVirtually none (2%) of the respondents had either floor or ceiling effects, indicating the IADCQ covers an ideal range of burden. A single-factor model obtained appropriate goodness of fit and provided evidence that a simple sum score of the 12 items of IADCQ can be used to measure AD caregiver’s burden. Scales-level reliability was supported with a coefficient alpha of 0.93 and an intra-class correlation coefficient (for test-retest reliability) of 0.68 (95% CI: 0.50–0.80). Low-moderate negative correlations were observed between the IADCQ and scales of the SF-12v2.ConclusionsThe study findings suggest the IADCQ has appropriate psychometric characteristics as a unidimensional, Web-based measure of AD caregiver burden and is supported by strong model fit statistics from CFA, high degree of item-level reliability, good internal consistency, moderate test-retest reliability, and moderate convergent validity. Additional validation of the IADCQ is warranted to ensure invariance between the paper-based and Web-based administration and to determine an appropriate responder definition.

Depressive symptoms in caregivers of patients with dementia: demographic variables and burden

“…Individuals suffering from dementia are affected by a progressive and significant global deterioration and, consequently, might require longer assistance in the advanced stage of the illness. 2 , 3 The person who takes care of a patient with dementia is known as a caregiver; in most cases, the caregiver is a family member. 4 …”

How best to assess quality of life in informal carers of people with dementia; A systematic review of existing outcome measures

“…One study was identified reporting on evaluation of the internal consistency, reliability and structural validity of this instrument [ 41 ]. Assessment of structural validity using confirmatory factor analysis confirmed unidimensionality of the scale.…”

“…There is also considerable variation in the settings and samples of included studies. Four studies [ 31 , 41 , 43 , 44 ] included only carers of people with Alzheimer’s disease, meaning that the results would not be generalizable to informal carers of people with other types of dementia. The studies on the QOL-AD (CQOL version) [ 43 , 44 ] and the SF-36 [ 31 ] used versions of the questionnaires in Portuguese and Argentinian respectively.…”

Development of an Item Pool for a Needs-Based Measure of Quality of Life of Carers of a Family Member with Dementia

“…Key demographic characteristics of the qualitative interview sample are shown in table 2. In addition, the sample had been caring an average of 54 months (range 5-180), 33 were co-resident with the person cared for, diagnoses of those cared for were Alzheimer's disease (18), vascular dementia (13), other dementia (9), type not known (2). Twelve of the people with dementia could not be left alone, 24 could be alone for up to half a day and seven for a whole day.…”

“…A systematic review [7] adhering to COSMIN methodology [15] identified ten measures used with dementia carer samples. Three of these measures were developed specifically for dementia carers, but two lacked evidence to recommend use [16,17] The third, Impact of Alzheimer Disease on Caregiver Questionnaire [18], is a unidimensional scale with fair to excellent psychometric qualities. However, further evaluation was advised including extending the sample to an older age group and to include carers of those with dementia other than Alzheimer's disease.…”