Yonago Acta medica 2009;52:11–20

Wechsler Adult Intelligence Scale, 3rd Edition (WAIS-III):
Usefulness in the Early Detection of Alzheimer’s Disease
Yukihiro Izawa*†‡, Katsuya Urakami§#, Tomoyuki Kojima¶** and Eisaku Ohama**Department of Neuropathology, Institute of Neurological Sciences, Tottori University Facultyof Medicine, Yonago 683-8504, †Clinic of Rehabilitation, Okayama Rehabilitation Hospital,
Okayama 703-8272, ‡Clinic of Rehabilitation, Hakuai Hospital, Yonago 683-0853, §Department of Biological Regulation, School of Health Science, Tottori University Faculty of Medicine,
Yonago 683-8503, #Clinic of Neurology, Shinsei Hospital, Kurayoshi 682-0017, ¶Ichikawa Consultancy for Higher Brain Dysfunction, Ichikawa 272-0023 and **Sendai Medical and Welfare
Vocational College, Sendai 980-0023 Japan
We examined Alzheimer’s disease (AD) patients using a Japanese version of the Wechsler
Adult Intelligence Scale, 3rd Edition (JWAIS-III) to clarify i) the significance of expansion of
the indicated age range, ii) the characteristics of cognitive impairment in AD patients and iii)
the efficacy of th neuropsychological assessment for the early detection of AD using the Digit
Symbol subtest, which involves attention and episodic memory, and the Pairing supplementary test, which relates to digit symbol-incidental learning. The JWAIS-III was given to 43 AD
patients (12 males and 31 females; mean age, 80.9 ± 6.3 years, who fulfilled the diagnostic criteria for AD on the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSMIV) and the National Institute of Neurological and Communicative Disorders and Stroke
and the Alzheimer’s Disease and Related Disorders Association. Severity of dementia of thepatients was classified according to Functional Assessment Staging (F) as follows: 9 patientsin F3 (borderline), 15 in F4 (mild AD), 12 in F5 (moderate AD), 7 in F6 (somewhat severe AD)
and none in F7 (severe AD). i) Mean intelligence quotients (IQs) were: Full Scale IQ 84.3 ±
14.0, Verbal IQ 84.6 ± 12.5 and Performance IQ 86.9 ± 15.5. Comparison of IQs and subtest
scores of the patients aged 75 years or older assessed by standard scores for 70 to 74 years ofage, which is the upper limit of the indicated age range on the WAIS-R (the previous versionof the WAIS-III), with those assessed by the standard scores for the appropriate age revealed
that the former were significantly lower in IQ and all subtest scores. ii) Significant differences were noted among the severities of dementia in the scores of 7 subtests for Similarities,
Comprehension, Arithmetic, Digit Span, Letter-Number Sequencing, Digit Symbol and Symbol Search. iii) When both the Digit Symbol subtest scores of 7 points or more and the Digit
Sumbol-Pairing supplementary test scores exceeding 10% of the cumulative percentile wereregarded as normal, 11 of 15 (73.3%) patients in F4 (mild AD) could be detected. These findings suggest that i) expansion of the indicated age range in the WAIS-III allows a more valid
assessment of cognitive function in AD patients, ii) a marked decline in abstract thinking andverbal problem-solving ability and relative preservation of Perceptual organization are characteristics of cognitive impairment in AD patients and iii) a combination of the Digit Symbol
subtest with the Pairing supplementary test is useful for the early detection of AD.
Key words: Alzheimer’s disease; Digit Symbol; Pairing; screening test for dementia; Wechsler
Adult Intelligence Scale
Abbreviations: AD, Alzheimer’s disease; ANOVA, one-way analysis of variance; F, Functional assessment staging; IQ, intelligence quotient; JMMSE, Japanese version of the MMSE;JWAIS-III, Japanese version of the WAIS-III; MMSE, Mini-Mental
State Examination; WAIS-III, Wechsler Adult Intelligence Scale, 3rd Edition; WAIS-R, WAIS-Revised

11

Y. Izawa et al.

Currently one in every 10 persons aged 65 andover has dementia, making it a “common disease”(Urakami et al., 1998; Ishikawa and Ikeda, 2007;
Wakutani et al., 2007). In addition, the initial
symptoms of dementia such as mild anmesia tend
to be overlooked because they are considered aninevitable consequence of aging (Urakami, 2007).
Thus, the difficulty of early detection of dementia
is a major problem for clinicians involved in dementia.
The Mini-Mental State Examination (MMSE)(Folstein et al., 1975) is frequently used in clinicalpractice for the neuropsychological assessment ofintelligence in Alzheimer's disease (AD) patients.
The test mainly assesses recent memory andworking memory from a neuropsychological perspective in a short time. However, for a better understanding of the pathophysiology of AD (Meguro
and Yamadori, 2000), we need a comprehensive
assessment of intelligence including social andbehavioral abilities. The most commonly used
test for intelligence in clinical use is the Wechsler
Adult Intelligence Scale, 3rd Edition (WAIS-III)(Wechsler, 1997) published in 1997; the current
Japanese version (JWAIS-III) (Fujita et al., 2006a)
was published in 2006. On the JWAIS-III, someexamination items were modified in accordancewith Japanese culture, history, education and social
background, and its validity has been confirmed,
similar to the WAIS-III. On the WAIS-III the upper limit of indicated age range has been expandedfrom 74 years to 89 years, and new subtests wereadded to measure the abilities of working memoryand of thinking visually and deductively whichwere not included on the WAIS-Revised (WAIS-R)(Wechsler, 1981; Shinagawa et al., 1990). Several

previous studies have used the WAIS-R to analyze
the characteristics of intelligence in AD patients(Fuld, 1984; Utsumi et al., 1995; Nishihagi etal., 2006), but a general consensus has yet to bereached. One study did use the WAIS-III to assess
the intelligence of AD patients (Teng et al., 2007),
but to our knowledge there are no reports comprehensively studying the characteristics of intelligence in AD patients.
In the present study, we examined AD patients using JWAIS-III to clarify i) the significanceof expansion of the indicated age range, ii) the
characteristic of cognitive impairment in AD patients and iii) the efficacy of combining the Digit
Symbol subtest (Digit Symbol) with the Pairing
supplementary test (Pairing) as an indicator of episodic memory for the early detection of AD.
Subjects and Methods
Subjects
The subjects were 43 AD patients, 12 males and
31 females, who were outpatients in the Clinic of
Neurology, Shinsei Hospital, Kurayoshi City, Japan. Their ages ranged from 56 to 93 years, witha mean of 80.9 ± 6.3 years. The patients were diagnosed as AD based on the criteria of the Diagnostic and Statistical Manual of Mental Disorders,
4th edition (American Psychiatric Association,1994) and the National Institute of Neurologicaland Communicative Disorders and Stroke and the
Alzheimer's Disease and Related Disorders Association (McKhann et al., 1984). Functional Assessment Staging (F), a behavioral and functional
assessment scale (Reisberg et al., 1982, 1984), wasTable 1. Intelligence factors and their subtests on the JWAIS-III
Verbal Comprehension
SubtestWorking Memory

Vocabulary
Arithmetic
Similarities
Digit Span
Information
Letter-Number Sequencing*Comprehension		

Perceptual Organization

Processing Speed

Picture Completion
Block Design
Matrix Reasoning*
Picture Arrangement

Digit Symbol
Symbol Search*

JWAIS-III, Japanese version of the Wechsler Adult Intelligence Scale, 3rd Edition.
* Newly added subtests.

12

WAIS-III for detection of AD

used as an indicator of the severity of dementia as
follows: F1, normal; F2, appropriate for age; F3,
borderline; F4, mild AD; F5, moderate AD; F6,
somewhat severe AD and F7, severe AD. In thepresent study, 9 patients were in F3, 15 in F4, 12
in F5, 7 in F6 and none in F7.

diately after finished Digit Symbol, the examinees
are required to write the symbols to blanks under
the digits by episodic memory.
Japanese version of the Mini-Mental State Examination (JMMSE)
The JMMSE (Mori et al., 1985) was given at
about the same time as the JWAIS-III. The MMSE
(Folstein et al., 1975; Mori et al., 1985) is a simple
intelligence test for the multifaceted assessmentof cognitive functions through the administrationof 11 subtests: time orientation, place orientation,
immediate memory, recent memory, calculation,naming, recitation, behavior in response to verbal
directions, reading comprehension, writing letters and copying patterns. A perfect score on the
MMSE is 30 points and the cutoff for dementia/
non-dementia is 23/24 points.

Tests administered
JWAIS-IIIThe Object Assembly subtest was excluded fromthe present analysis because this subtest has alower reliability coefficient than all of the othersubtests (Fujita et al., 2006b). Therefore, in thisstudy a total of 13 subtests were administered,consisting of 7 subtests for the Verbal scale and
6 for the Performance scale. On the JWAISIII, 4 intelligence factors have been used basedon the results of factor analysis for standardized
data (Fujita et al., 2006b). The intelligence factors and their subtests are shown in Table 1. On
the WAIS-III, the upper limit of the indicated age
range was expanded from 74 to 89 years in lightof the increased aging of society. Three new subtests, Letter-Number Sequencing, Matrix Reasoning and Symbol Search, were added to assess cognitive functions from many angles. Furthermore,
the Pairing supplementary test (Pairing) was also
added to assess Digit Symbol-incidental learning,which made it possible to assess both episodic
memory and sustained attention at the same time.
On the Digit Span subtest (Digit Span) standard
values for the numbers of digit spans recited correctly forward and backward, and for differencesin the numbers of digit spans between the twohave been reported, which makes it possible to assess cognitive function qualitatively.

Methods of tests administered
Taking into consideration the examinee’s fatigue,
the two tests were administered in 2 or 3 sessions,each of which took 1 h a day. These tests were
performed within a month and no changes inclinical symptoms were noted during that period.
Calculation of scaled scores for the 3 patients
whose ages exceeded 89 years, the indicated age
limit in WAIS-III, was done using the standard
scores for subjects aged 85 to 89 years.
Ethical considerations
The purpose of this study was explained to all
subjects and their families, and written consent
for test participation was obtained.
Statistical analysis

Explanation and procedure of Digit Symbol andPairing
Digit Symbol is a task of writing the symbols
paired with each digit. Examinees write thosesymbols paired with each digit to blanks from indicated models. Pairing is a recall task of the symbols paired with each digit used the subtest. Imme-SPSS Ver. 15, Windows version (SPSS, Tokyo,
Japan) was used for statistical analysis. A P valueless than 0.05 (P < 0.05) was considered significant, and that of 0.05 or more but less than 0.10
(0.05 ≤ P < 0.10) was considered to have a tendency towards significance.
13

Y. Izawa et al.

Table 2. IQ scores (mean ± SD) by JWAIS-III and JMMSE scores in each severity of dementia in 43
AD patients
JWAIS-III
Full Scale IQ
Verbal IQ
Performance IQ
JMMSE*Overall mean

F3 [9]

F4 [15]F5 [12]F6 [7]

84.3 ± 14.0
84.6 ± 12.5
86.9 ± 15.5
20.2 ± 4.6

92.6 ± 14.5
93.0 ± 12.6
93.6 ± 15.7
25.2 ± 2.2

90.9 ± 11.9
90.9 ± 9.3
92.7 ± 14.8
22.4 ± 2.2

76.8 ± 8.9
76.2 ± 7.4
81.9 ± 12.4
17.8 ± 2.9

72.4 ± 11.3
74.6 ± 10.6
74.3 ± 12.8
13.4 ± 1.7

AD, Alzheimer’s disease; F, Functional assessment staging: F3, borderline; F4, mild AD; F5, moderate AD; F6, somewhat
severe AD; IQ, intelligence quotient; JMMSE, Japanese version of the Mini-Mental State Examination; JWAIS-III, Japaneseversion of the Wechsler Adult Intelligence Scale, 3rd Edition.
[ ], number of patients.
* A perfect score 30, cutoff point for dementia/non-dementia 23/24.

Table 3. Scaled scores (mean ± SD) on the JWAIS-III subtests for each severity of dementia in 43
AD patients
SubtestOverall mean

F3 [9]

F4 [15]F5 [12]F6 [7]

Verbal Scale
Vocabulary
Similarities
Information
Comprehension
Arithmetic
Digit Span
Letter-Number Sequencing

8.0 ± 2.1
6.5 ± 3.1
7.3 ± 1.8
6.7 ± 2.7
8.3 ± 2.8
8.9 ± 2.7
7.5 ± 3.2

8.8 ± 2.0
8.4 ± 2.7
8.3 ± 2.7
7.9 ± 3.0
10.0 ± 3.4
9.9 ± 3.9
10.7 ± 3.7

8.8 ± 2.5
7.7 ± 2.2
7.4 ± 1.2
7.7 ± 2.99.3 ± 2.8
10.3 ± 2.0
7.6 ± 2.7

7.2 ± 1.4
4.8 ± 2.6
6.8 ± 1.2
5.8 ± 1.8
6.9 ± 1.6
6.8 ± 1.6
7.1 ± 1.0

6.9 ± 1.7
4.0 ± 3.1
6.6 ± 2.1
4.7 ± 1.8
6.4 ± 1.1
8.3 ± 1.4
4.0 ± 1.9

Performance Scale
Picture Completion
Block Design
Matrix Reasoning
Picture Arrangement
Digit Symbol
Symbol Search

7.8 ± 3.2
8.1 ± 2.7
9.0 ± 3.0
8.3 ± 2.7
7.5 ± 2.7
7.2 ± 3.0

9.0 ± 2.9
9.1 ± 2.3
9.2 ± 2.8
9.9 ± 2.6
8.6 ± 3.0
9.1 ± 3.9

9.0 ± 3.2
8.8 ± 2.3
9.7 ± 3.2
9.0 ± 3.0
8.5 ± 2.4
7.9 ± 2.1

6.2 ± 2.9
7.5 ± 2.5
9.1 ± 2.7
7.2 ± 2.3
7.2 ± 2.5
6.4 ± 2.0

6.7 ± 2.9
6.1 ± 3.4
6.7 ± 2.4
7.0 ± 1.6
4.6 ± 1.3
4.3 ± 2.8

F, Functional assessment staging: F3, borderline; F4, mild Alzheimer’s disease (AD); F5, moderate AD; F6, somewhat severe AD.
[ ], number of patients.

formance IQ was 86.9 ± 15.5. The mean JMMSE
score was 20.2 ± 4.6 points. A significant correlation, moderate in degree, was noted between
IQs and JMMSE scores. Scores for Spearman’s
correlation coefficient were r = 0.690 (P < 0.01)
between Full Scale IQ and JMMSE, r = 0.683 (P< 0.01) between Verbal IQ and JMMSE, r = 0.595(P < 0.01) between Performance IQ and JMMSE.
Table 3 shows scaled scores (mean ± SD) on each
subtest of the JWAIS-III.

Results
IQ scores by the JWAIS-III and JMMSE
scoresThe overall mean intelligence quotient (IQ) scoresby the JWAIS-III and JMMSE scores in the 43
AD patients are shown in Table 2, as well as thosefor each severity of dementia. Full Scale IQ was
84.3 ± 14.0, Verbal IQ was 84.6 ± 12.5, and Per-

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WAIS-III for detection of AD

Table 4. JWAIS-III IQ scores for the 38 AD patients exceeding 75 years of age obtained by raw
score-scaled score conversion tables
IQ

Conversion table
for the age group70–74 years

Full Scale IQ
Verbal IQ
Performance IQ

Conversion table
Difference
for the appropriate		
age group*

75.50
78.71
76.08

84.00
84.66
86.18

8.50
5.95
10.10

Probability< 0.05< 0.05< 0.05AD, Alzheimer’s disease; IQ, intelligence quotient; JWAIS-III, Japanese version of the Wechsler Adult Intelligence Scale,
3rd Edition.
* IQs for the 3 patients exceeding 89 years of age were obtained using the standard scores of subjects for 85–89 years.

Table 5. Scaled scores on the subtests of the JWAIS-III obtained by raw score-scaled score conversion tables
SubtestConversion table
for the age group70–74 years

Conversion table
Difference
for the appropriate		
age group

Probability

Verbal Scale
Vocabulary
Similarities
Information
Comprehension
Arithmetic
Digit Span
Letter-Number Sequencing

7.26
5.47
6.84
5.89
6.79
8.00
5.55

8.24
6.45
7.34
6.84
8.03
8.95
7.42

0.98
0.98
0.50
0.95
1.24
0.95
1.87

< 0.05< 0.05< 0.05< 0.05< 0.05< 0.05< 0.05

Performance Scale
Picture Completion
Block Design
Matrix Reasoning
Picture Arrangement
Digit Symbol
Symbol Search

5.89
6.74
7.61
6.32
5.63
5.66

7.79
7.89
8.89
8.16
7.47
6.92

1.90
1.15
1.28
1.84
1.84
1.26

< 0.05< 0.05< 0.05< 0.05< 0.05< 0.05JWAIS-III, Japanese version of the Wechsler Adult Intelligence Scale, 3rd Edition.

by scaled scores for the JWAIS-III, showing significant differences in Full Scale-, Verbal- andPerformance-IQ scores. When the conversion
table for patients aged 70 to 74 years was used, all
IQ scores, particularly the Performance-IQ score,
were low.
Table 5 shows the mean scaled scores for thesubtests, showing significant differences in each
subtest. When a conversion table for patients
aged 70 to 74 years was used, scaled scores were
low in all subtests. Relatively marked differenceswere noted in scores of Arithmetic and LetterNumber Sequencing on the verbal scale. TheseIQs and scaled subtest scores obtainedby the indicated age range for raw scorescaled score conversion tables
On the WAIS-R, the upper limit of the indicatedage range was 74 years. Among the 38 patients
aged 75 years and older in our study, we analyzed
IQs and scaled scores obtained by a raw scorescaled score conversion table for patients aged 70
to 74 years and those obtained by a conversion
table for the appropriate age group using t-tests.
Table 4 shows the mean IQ scores obtained15

Y. Izawa et al.

Table 6. Correlations of JWAIS-III subtest scores with severities of dementia
SubtestEffect of severity

Multiple comparisonsMSe

Verbal Scale
Vocabulary
NS
Similarities*
Information
NS
Comprehension**
Arithmetic*/**
Digit Span*
Letter-Number Sequencing *F3 > F5, F3 > F6, F4 > F5, F4 > F6 (Bonferroni’s procedure)

6.64

F3 > F6, F4 > F6
F3 > F5, F3 > F6/F4 > F5, F4 > F6
F4 > F5
F3 > F6, F4 > F6, F5 > F6

(Bonferroni’s procedure)(Bonferroni’s procedure)(Tamhane’s procedure)(Tamhane’s procedure)

6.19
6.15
5.47
6.22

Performance Scale
Picture Completion
Block Design
Matrix Reasoning
Picture Arrangement
Digit Symbol
Symbol Search

No significant combination
F3 > F6, F4 > F6
F3 > F6, F4 > F6

(Bonferroni’s procedure)(Bonferroni’s procedure)(Bonferroni’s procedure)

6.57
5.78
7.03

NS
NS
NS
*
*
*

*P < 0.05**P < 0.10, indicating a tendency towards significance.
F, Functional Assessment Staging: F3, borderline; F4, mild Alzheimer’s disease (AD); F5, moderate AD; F6, somewhat severe AD; JWAIS-III, Japanese version of the Wechsler Adult Intelligence Scale, 3rd Edition; MSe, inter-group square sum/
degrees of freedom; NS, not significant.

was noted in 8 of the 13 subtests: Similarities, Comprehension, Arithmetic, Digit Span, Letter-Number
Sequencing, Picture Arrangement, Digit Symbol andSymbol Search [F(3, 39) = 6.72, 3.62, 4.85, 5.70, 9.55,
2.90, 5.04 and 5.11, respectively]. In the 8 subtests,
there were significant differences in scores among
severities of dementia as shown in Table 6.

are the subtests for measuring working memory.
All subtests for the performance scale showed differences of more than 1 point.
Comparison of scores among subtests andamong severities of dementia
One-way analysis of variance (ANOVA) revealed
significant differences in scores among the subtests[F(12, 546) = 3.30]. Multiple comparisons using
Tamhane's procedure revealed significant differences in scores between the Similarities subtest(Similarities) and Digit Span, Similarities and Matrix Reasoning, Comprehension and Digit Span andComprehension and Matrix Reasoning (inter-groupsquare sum/degrees of freedom = 7.71). Scores for
Similarities and Comprehension were significantly
lower than those for Digit Span and Matrix Reasoning. Differences between other subtests were
not significant.
Among severities, differences in scores foreach subtest were analyzed with ANOVA using the
F scale as an inter-examinee factor. Multiple comparison analysis was also conducted with subtests
where severity of dementia had a main effect which

Correlation of Pairing with Delayed recall of
3 words
We analyzed the correlation of scores for the Pairing, a newly added supplementary test for the Digit
Symbol of the WAIS-III, with those of the Delayedrecall of 3 words on the JMMSE. We divided thescores for each test into “good” and “poor” according to the standard data for the Pairing (Fujita et al.,2006c): the scores showing a cumulative percentageof 11% or more were classified as “good” and thoseless than 11%, as “poor” (Table 7). In the Delayedrecall of 3 words in the JMMSE, a correct recall of
2 or 3 words was classified as “good” and that of 1
or none, as “poor”. In both tests, 8 patients were rated as good and 24 patients, poor. Five patients weregood in the Pairing but poor in the Delayed recall
16

WAIS-III for detection of AD

Table 7. Classification of scores for
Digit Symbol and Pairing
Good
Score: 7 points or more in the Digit Symbol subtest
Cumulative percentage: 11% or more in the
Pairing supplementary test
Poor
Score: less than 7 points in the Digit Symbol subtest
Cumulative percentage: less than 11% in
the Pairing supplementary test

Table 8. Number of patients in each severity of dementia
based on the scores for Digit Symbol and Pairing
Classification of scores

F3 F4

F5

F6 Total

Good in both Digit Symbol and Pairing
Good in Digit Symbol and poor in Pairing
Poor in Digit Symbol and good in Pairing
Poor in both Digit Symbol and Pairing

6
1
1
1

4
7
1
3

0
8
1
3

0
1
1
5

10
17
4
12

Total

9

15 12

7

43

F, Functional assessment staging: F3, borderline; F4, mild Alzheimer’s disease (AD); F5, moderate AD; F6, somewhat severe AD.

dard data have 1.45 ± 1.28 digits (minimum: 1.10,
maximum: 1.79) as an overall mean (Fujita et al.,2006c). Compared to the standard data there wasno difference in span in each severity of dementia
group for AD patients. There was also no correlation among severities of dementia in AD patients.

of 3 words. Six patients were poor in the Pairing
but good in the Delayed recall of 3 words. Analysis
with Fisher’s exact test revealed a significant correlation between the Pairing and the Delayed recall of 3
words.
Scores for the Digit Symbol and Pairing ineach severity of dementia

Discussion

Based on the scores for Digit Symbol and Pairing, the patients were divided into good and poorgroups. On the Digit Symbol, scores of 7 points
or more (–1 SD of the standard scaled score) werecalled good, and those less than 7 points werecalled poor. On the Pairing, cumulative percentages (Fujita et al., 2006c) of 11% or more were called
good, and those less than 11% were called poor.
As shown in Table 8, when both a Digit Symbolscore of 7 points or more and scores on the Digit
Symbol-Pairing supplementary test 11% and moreof the cumulative percentile were regarded as normal, 3 of 9 (33.3%) F3 patients (borderline), 11 of
15 (73.3%) F4 patients (mild AD), 12 of 12 (100 %)F5 patients (moderate AD) and 7 of 7 (100 %) F6
patients (somewhat severe AD) could be detected.

In previous studies using the WAIS-R, cognitive
function in individuals aged 75 years and over was
frequently assessed using reference values for the
70 to 74 year age group. The present analysis of 38
patients with AD revealed that both scaled scoresin the subtests and IQs obtained by reference values for the appropriate age group were significantly
higher than those obtained by reference values forthe 70- to 74-year age group. The difference wasmore prominent in Arithmetic and Letter-Number
Sequencing subtests for working memory and in all
subtests of the performance scale which are related
to fluid intelligence. Thus, it was suggested that the
expansion of the indicated age range in the WAISIII allowed valid assessment of cognitive functionin AD patients aged 75 years and over.
Several previous studies evaluating intelligence of AD patients using the WAIS-R haveshared the views that in healthy adult performance
intelligence decreases with age while verbal intelligence is relatively preserved and that AD patients
have a marked decrease in performance intelligence (Fleischmann, 1994; Utsumi et al., 1995).
However, there is another view that a decline in

Difference between the longest digit span
forward and the longest digit span backward on the Digit Span test
The difference between the longest digit span forward and the longest digit span backward was 1.22
digits in F3 patients, 1.60 in F4, 0.92 in F5 and 1.43
in F6, with an overall mean of 1.30 digits. Stan17

Y. Izawa et al.

crystallized intelligence, in which verbal intelligence is a major component, is characteristic of
AD patients (Larrabee et al., 1985; Matsuda, 1998).
The 4 subtests included in verbal comprehension nearly correspond to crystallized intelligencereported by Horn et al. (1985). The term, verbal
comprehension indicates whole language ability
including being able to speak, think logically, reason, and express one’s self, in addition to the ability
to understand language. It is generally believedthat crystallized intelligence, which is constructed
through education and learning, is little affected byaging compared with fluid intelligence, the ability
to adapt to new situations (Horn, 1985; Kaufman,
1990; Fleischmann, 1994). The subtests for Vocabulary and Information involve semantic memory.
In the present study, there was no obvious difference in the scores for each severity of dementia
between the two subtests, suggesting that this typeof memory is relatively preserved even in the F6
patients. In contrast, the scores for the subtests
Similarities and Comprehension decreased with theprogress of dementia. These results were similar to
those of Matsuda (1998) and Nishihagi et al. (2006).
These findings suggest that a decrease in the abilities to think logically and categorically (Kita, 1998)
as measured by the subtest for Similarities, andthose to understand matters related to everyday
life and to solve problems using past experiences(Kobayashi and Fukunaga, 1995) as measured by
the subtest for Comprehension, is characteristic ofintellectual impairment in AD.
In Arithmetic, there were significant differences in the scores between borderline (F3) andmoderate (F5) or more severe (F6) AD patients,
showing that the score for the subtest decreased
rapidly at the stage of moderate dementia. The
subtest for Digit Span consists of two tasks: digit
span forward and digit span backward. While
the former involves immediate memory, the latter requires parallel processing (the figures are
rearranged in reverse order while the indicatedstimuli are maintained), which is a task supported
by working memory. Thus, in the test for digit
span backward the information processing loadincreases, which restricts the number of digit spanscorrectly recited. Kaplan et al. (1991) reported that
attention impairment is quite likely when there is amarked difference in the number of digit spans correctly recited forward and backward. Attention described here means sustained and divided attentiveness during task performance, which Lezak called
mental tracking (Kashima et al., 2005). Perry and
Hodges (1999) reported the impairment of divided
attention in AD. They stated that divided attention
and aspects of selective attention are particularly
vulnerable while sustained attention is relatively
preserved in the early stages of AD. In the present
study, the number of digit spans correctly recited
forward and backward was almost the same as thatin healthy individuals, and the scaled score calculated as the sum of the digit span forward and thedigit span backward was also relatively high, andthere was no difference in scores in each severityof dementia. Besides, the scores for Digit Spanremained higher than those of other subtests forworking memory. From these results, we may conclude that the test for digit span is a rather simple
task and does not directly reflect the divided and/or selected attention, and we think the validity of
Digit Span as a test to measure attention must be
reexamined further. Letter-Number Sequencing
was thought up as a new subtest for working memory. In this study, there were no significant differences between borderline and moderate AD cases,
but markedly decreased in F6 patients (somewhat
severe AD).
Perceptual organization is an intelligencefactor on the Performance scale, and indicates theability to recognize interactions between stimulus
elements and to construct these elements into a
unified form (Kita, 1998). One study has describedthat visual and spatial cognitive impairments appear in the relatively early stages of AD (Sato et al.,2001). In the present study, however, we found no
significant differences in the scores of the subtests
for perceptual organization among severities of dementia, suggesting that the ability to recognize andprocess information about visual stimuli, which
includes visual and spatial cognitive functions andvisual spatial construction, is preserved at least up
to F5 (moderate AD). In particular, deductive rea18

WAIS-III for detection of AD

soning ability measured by Matrix Reasoning waspreserved in F6 (somewhat severe AD) patients,suggesting that this ability is highly resistant in
AD.
There were significant differences in thescores on the subtests for Digit Symbol and Symbol Search among the severities of dementia, suggesting that the speed of processing, which is supported by not only sustained attention, but divided
and selected attention, decreases with progressionof dementia.
There are two ways to use the WAIS- III for
the detection of AD: one is to determine the presence or absence of dementia and its severity basedon quantitative assessment of specific subtests, andthe other is to detect AD based on the characteristic patterns of the scores in the subtests. In thequantitative assessment of specific subtests, it isimportant that intelligence levels of AD patientsare closely related to their pre-morbid levels. In
patients with a high pre-morbid intelligence level,
dementia might be overlooked in the early stages.
In the present study there were no subtests showing
an obvious decrease of scaled scores in both borderline (F3) and mild dementia (F4) cases. Thus
it was difficult to detect AD based on the scaled
scores of the subtests alone.
There are some studies (Fuld, 1984; Utsumi
et al., 1995; Nishihagi et al., 2006), using subtest
profiles from the WAIS-R for the detection of AD.
In the WAIS-III, however, the upper limit of theindicated age was expanded from 74 to 89 years
old, and new subtests were added. Therefore, thescaled scores from the WAIS-R cannot simply beapplied to the WAIS-III.
In AD, impairment of recent and episodic
memory appears in the early stages, and impairment of remote (distant) memory becomes obvious with the progression of dementia. Immediate
memory is quite likely to be preserved even atadvanced stages (Furuta and Mimura, 2006). In
studies using the JMMSE, it has been reported
that impairment of recent memory measured by
the delayed recall of 3 words is most useful for the
early detection of AD (Furuta and Mimura, 2006).
Kaplan et al. (1991) have reported that processing

functions such as coordinated movement, memory,visual sensory perception, writing speed, and writing precision influence the Digit Symbol scores. In
light of this finding, Incidental Memory and Copy
supplementary tests were added to the WAIS-III
in order to measure memory and writing speed,
respectively. The Pairing is a part of Incidental
Memory and is administered after the Digit Symbol is completed. Based on memory on the Digit
Symbol, examinees have to recall and write thedigit symbol corresponding to the figures shownin the subtest. In the present study, scores for the
Pairing correlate significantly with the Delayedrecall of 3 word scores in the JMMSE, suggesting that the Pairing test is useful in screening fordementia in AD. Furthermore, when the subjects
were divided into the “good” and “poor” groups,
according to the performances in the Digit Symbol
and the Pairing, we could detect 73.3% of the patients in F4 (mild dementia of AD). These results
are equivalent to the specificity of 84% and moreaccording to the norm of the WAIS-III (Fujita etal., 2006b, 2006c), and indicate that combining theDigit Symbol and the Pairing tests is useful for the
early detection of AD.
Acknowledgments: The authors wish to thank Mr. Iori
Takeda and staff members of the Rehabilitation Room of
Shinsei Hospital for their help in giving the WAIS-III tests.
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Received December 8, 2008; accepted January 5, 2009
Corresponding author: Yukihiro Izawa

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