Professor Timothy Kwok of Jockey Club Centre for positive ageing, the Chinese University of Hong Kong, explores how to reliably evaluate older adults with severe dementia
Dementia is characterised by substantial cognitive impairments and interference of the performance in daily living activities. When the disease progresses to a severe stage, all cognitive domains have further deterioration with noticeably short attention span, poor memory, and limited verbal output. The individuals also become highly dependent on everyday activities. How to reliably measure cognitive changes in severely demented older adults? How to enhance the quality of services for them when they are hardly to express themselves? These questions remain as challenges in the field as there are limited reliable evaluation tools and related studies available locally.
The commonly used psychological tests are found to have floor effects when applied to people with severe dementia. The long testing time of these tests also intolerable to them. 1Therefore, the cognitive functions at severe stage dementia are regarded as “untestable” traditionally. 1 Besides, Quality of Life (QoL) is a multifaceted concept that covers subjective and objective criteria. Most scales are developed for mild to moderate dementia, and related scales rely on self-reporting experiences. The validity of these scales becomes questionable when measuring the QoL of severe dementia. 2
Our team reviewed two scales that are specifically designed for severe dementia, the Cognitive Test for Severe Dementia (CTSD)3, and the Quality of Life in Late-Stage Dementia (QUALID)4. The original versions of both scales are in English. We did a study to validate the Chinese versions of CTSD (CTSD-C) and QUALID (QUALID-C) in seven residential care homes and hope to answer those questions.5
The Cognitive Test for Severe Dementia (CTSD) is developed by Tanaka et al in 2015. It has been shown to be significantly correlated with other cognitive assessments and sensitive to measure the cognitive changes in severe dementia over time without floor effects. 3,6 It is a performance-based cognitive test, and the implementation time is approximately 10 minutes. The equipment required is daily used items such as a clock and a comb, etc. The scale comprises 13 items across seven cognitive domains including orientation, memory, and language. The maximum score is 30; higher scores indicate better cognitive function.3 Item 4 of the original version is the repetition of three words: “cherry blossoms”, “cat” and “train”, the word “cherry blossoms” is changed to “peach blossom” because of cultural relevancy as approved by the original author. 5 The QUALID scale is developed by Weiner et al in 2000. It has been shown to have good psychometric properties and has been translated and validated in different languages.4,7,8 The implementation time is less than ten minutes and completed by informant. The informant gives the rating according to a five-point scale over 11 items of observable behaviours, such as “appears sad” and “enjoys social interaction”, etc. The maximum score is 55; lower scores indicate better QoL.
In the validation study, the psycho-metric properties of the CTSD-C and QUALID-C were good and consistent with previous studies.5 The CTSD-C showed satisfactory internal consistency (Cronbach’s α = 0.86), good inter-rater reliability (ICC = 0.99), and good test-retest reliability (ICC = 0.96). Principal component analysis (PCA) obtained three factors; items loaded on factors 1 and 2 were similar to the original study. 3, The QUALID-C showed acceptable internal consistency (Cronbach’s α = 0.65), good inter-rater reliability (ICC = 0.99), and good test-retest reliability (ICC = 0.87). The PCA and items loaded on the factors were similar to previous findings and suggested the scale’s multidimensionality to measure QoL.7,8
We then applied the CTSD-C and QUALID-C in two long-term care settings from January 2020 to June 2021. Total 54 participants with severe dementia (male=7, female=47) were assessed, their mean age was 84.83 ages + 12.25. Most of them were diagnosed with Alzheimer’s disease (93.20%), and 6.80% were vascular dementia or mixed dementia. The distribution of education was 38.91% received no formal education, 24.10 % had primary education, and 37.10% had secondary or above education. The mean scores of the CTSD-C and QUALID-C were 13.06 + 8.25 and 24.45 + 5.86 respectively. The mean CTSD-C was lower when compared to previous findings (mean scores = 14.90 – 15.70), 3,6 and the mean QUALID-C was comparable to earlier studies.4,7,8
The relationship between QoL and cognition in dementia
We also tried to address the interesting question about the relationship between QoL and cognition in dementia. Previous studies indicate the complicated relationship between these two constructs, results varying with the stages of dementia, and format of assessing the QoL, etc.9 In our sample (n=122), the analysis of Pearson coefficient between the QULAID-C and the CTSD-C was 0.02, p=0.84; cognition was not correlated with QoL in severe dementia. It supports earlier studies that cognition and QoL are two independent constructs in dementia.9,10
The CTSD-C and QUALID-C are valid and reliable scales to measure the cognitive function and QoL for Chinese older adults with severe dementia. They can be utilised in different settings conveniently such as residential homes because of the short implementation time and no special equipment required. It can enable us to evaluate the effectiveness of treatment and future research work.
Suet-Lai Leung (a,b), Timothy C. Y. Kwok (b,c)
a School of Medical and Health Sciences, Tung Wah College, Mong Kok, Hong Kong
b Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, Hong Kong
c Jockey Club Centre for Positive Ageing, Shatin, Hong Kong
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