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One of the key clinical features of early symptoms of dementia is the cognitive deficits in everyday activities. Until a few years ago, it was considered that early-stage dementia is typically characterized primarily by memory impairment. In the latest survey for early-stage dementia, executive dysfunction has been attracting attention to not only memory impairment in the significant cognitive deficits. The cognitive deficits are often mild and may get worse very gradually, but it has been suggested that executive dysfunction affects the Instrumental activities of daily living (IADL) of early-stage dementia.
Executive function consists of complex attention, working memory, verbal and visual organization, planning, judgment, and reasoning. IADL includes activities related to independence, organization, and judgment abilities, such as the ability to use a telephone, shopping, food preparation, housekeeping, laundry, transportation, responsibility for one’s own medication, and handling finances. In the recent studies, executive dysfunction and IADL impairment are thought to be associated with prefrontal dysfunction of mild cognitive impairment (MCI).
Several studies using executive function tests have revealed differences in performance between healthy control subjects and patients with Alzheimer's disease (AD) or mild cognitive impairment (MCI). However, some of the most widely used tests of executive functions, such as the Wisconsin Card Sorting Task (WCST) and the Trail Making Test (TMT), can be performed normally by patients with clear executive impairments. The observations are not consistent across all studies.
To assess executive functions in the context of more ecologically relevant behaviors, Wilson (1996) developed the Behavioral Assessment of Dysexecutive Syndrome (BADS). The BADS is a valid battery of tests which assesses problems in everyday behavior which are typically found in patients with dysexecutive syndromes. There are no studies which revealed the association between IADL and executive dysfunction using the BADS to patients with early-stage dementia, although executive function is an important cognitive function for individuals efficiently performs IADL.
The purpose of this study is to investigate the relationship between executive dysfunction and IADL in early-stage dementia.
Methods:
Participants
29 participants (6 male and 23 female) were recruited in the present study. Inclusion criteria were as follows: 1) age older than 60 years; 2) a Mini-Mental State Examination (MMSE) score > 20; 3) the Beck Depression Inventory (BDI) score ≦ 14; 4) absence of vascular lesions; 5) absence of psychiatric disease which could cause cognitive impairment.
Measurement Instruments
Executive function assessment
The Behavioral Assessment of Dysexecutive Syndrome (BADS)
The BADS (Kashima H, 2003) is a standardized battery that includes six subtests and two forms of the Dysexecutive Questionnaire (DEX). The six subtests consists of the Rule Shift Card Test, Action Program Test, Key Search Test, Temporal Judgment Test, Zoo Map Test, and Modified Six Elements Test. A profile score, ranging from 0(severely deficient) to 4 (normal performance), is determined of each subtest, and the sum of each subtest is calculated as the overall profile score. The maximum total score is 24. From the results, the overall classification is obtained: impaired, borderline, low average, average, high average, superior, and very superior. The DEX questionnaire comprises 20 items constructed to examine the range of problems associated with the dysexecutive syndrome. Two versions are used: DEX self-rating (patients) and DEX other-rating (caregivers). The maximum score is 80 points on each questionnaire.
In all cases, the BADS was performed on a single session and it took approximately 45 minutes on average.
Instrumental activities of daily living (IADL) assessment
The Instrumental Activities of Daily Living (IADL) scale is an appropriate instrument to assess independent living skills (Lawton, 1969). There are 8 domains of function measured with the IADL scale: using the telephone, shopping, food preparation, housekeeping, laundry, mode of transportation, responsibility for own medications, and ability to handle finances. A summary score ranges from 0 (low function, dependent) to 8 (high function, independent). Until this point, women were scored on all 8 domains of function, men were not scored in the domains of food preparation, housekeeping, and laundry. However, current recommendations are to assess all domains for both genders.
Analyses
Spearman’s correlation test was used to investigate the relationship between the BADS and the IADL scale, the BADS and sample descriptive data. The Mann-Whitney U test was used to detect difference between DLB and AD in relation to sample descriptive data, the BADS, and the IADL scale. We used the Statistical Package for Social Sciences (SPSS) version 21, at the 95% confidence level.
Ethical considerations
This study was approved by University of Tsukuba Faculty of Medicine, Ethics Committee. Written informed consent was obtained from participants, before the initiation of any research procedures.
Results:
The BADS was performed on 27 inpatients and 2 outpatients (13 Dementia with Lewy bodies, 13 Alzheimer's disease, and 3 Suspected Dementia).
The BADS overall profile score was significantly correlated with MMSE score (r = 0.61; p < 0.01) and IADL score(r = 0.54; p < 0.01). There was no correlation between the BADS overall profile score and age (r = -0.20). The BADS overall profile score was correlated with DEX other-rating score(r = -0.48), but no correlation with DEX self-rating score(r = 0.03). Correlations between BADS subtests and IADL score were statistically significant(r = 0.41 to 0.49; p < 0.05), except for the Temporal Judgment Test(r = -0.04) and Modified Six Elements Test(r = 0.23). IADL score was correlated with DEX other-rating score(r = -0.67; p < 0.01), but no correlation with DEX self-rating score(r = -0.04).
There was no statistically significant differences between DLB patients and AD patients in age (patients mean = 74.75, SD = 7.61 [range 60 to 87]; p = 0.40), MMSE score (patients mean = 25.24, SD = 3.13 [range 21 to 30]; p = 0.56), IADL score (patients mean = 4.31, SD = 1.85 [range 1 to 8]; p = 0.56), BADS overall profile score (patients mean = 10.34, SD = 4.04 [range 3 to 19]; p = 0.77), DEX self-rating score (patients mean = 8.82, SD = 8.37 [range 0 to 29]; p = 0.25), and DEX other-rating score (patients mean = 16.94, SD = 17.99 [range 0 to 58]; p = 1.0).
The BADS overall profile score was 18 impaired, 5 borderline, 2 low average, and 4 average.
Conclusion:
The BADS was a useful battery that can evaluate the relevance of executive dysfunction and IADL. We found that executive function was associated with IADL. So, it is recommended that nurses should assess the executive function to patients with early-stage dementia. IADL score was significantly correlated with the 4 subtests. But, the Temporal Judgment Test was no correlation with IADL score. The Temporal Judgment Test was shown to be not appropriate for the evaluation of the relevance of executive function and IADL.
The BADS overall profile score was correlated with MMSE score, and 23 patients (79.3%) were classified into impaired or borderline. The presence of executive dysfunction in early-stage dementia was suggested. The BADS overall profile score was no correlation with age, and there was no significant difference between BLD and AD. In previous research, correlation between age and executive dysfunction has been suggested, and difference in the progression of executive dysfunction of BLD and AD has been shown by observation by psychiatrist. However, it was not evident in this study sample of early-stage dementia.
The evaluation of the executive dysfunction by patients (DEX self-rating) was lower than caregivers (DEX other-rating). It is considered that the evaluation of caregivers is important in the assessment of executive function to patients with early-stage dementia.