BRAIN

AND

LANGUAGE

42, 454-472 (1992)

Relation of Linguistic Communication Abilities of Alzheimer’s Patients to Stage of Disease KATHRYN

A. BAYLES, CHERYL K. TOMOEDA, AND MICHAEL W. TROSSET Department of Speech and Hearing Sciences, University

of Arizona

A battery of linguistic communication (L-C) tasks was administered to 152 Alzheimer’s disease patients in different stages of the disease and 60 normal elders. Subject performance data are used to construct a profile of L-C deficits by disease stage, as determined by ratings on the Global Deterioration Scale. Specification also is made of the L-C tasks on which mild Alzheimer’s patients perform like normal elders, the relative difficulty of various L-C processes, the disease stage in which the greatest change occurs in L-C functions, and the degree of variation in L-C for individuals at a particular level of dementia severity. o fwz Academic Press. Inc.

An extensive literature documents the deleterious effects of Alzheimer’s disease (AD) on linguistic communication (L-C) (Appell, Kertesz, & Fisman, 1982; Bayles, 1982; Bayles & Kaszniak, 1987; Bayles & Tomoeda, 1991; Cummings & Benson, 1983, Obler, 1983). Little information, however, has been published describing the profile of deficits in L-C abilities in relation to stage of disease. Scientists and clinicians lack an appreciation of how the score of an AD patient on a L-C test relates to the average score of normal individuals of the same age. Also lacking is information about when, in the disease course, AD patients can no longer perform basic L-C tasks, and the number of AD patients of a particular level of dementia severity whose performance on a particular test might pass for normal. Further, no data are published that provide information about the degree of variability that exists in performance on L-C tasks of individuals who are at the same level of dementia severity. With the support of a National Institute of Mental Health grant, the This study was supported by NIMH Grant ROl MH 40827. The authors acknowledge the contributions of time of the AD patients and their family members and normal control subjects and the support of the Alzheimer’s Association of Tucson and Phoenix. Address all correspondence and reprint requests to Kathryn A. Bayles at the Department of Speech and Hearing Sciences, University of Arizona, Tucson, AZ 85721. 454 0093-934x192 $5.OO Copyright 8 1992 by Academic Press, Inc. All rights of reproduction in any form reserved.

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TABLE 1 DEMOGRAPHICCHARACTERISTICSOF STUDY PARTICIPANTS

Demographic variables

AD

Controls

Sex Males Females

45 107

17 43

Age (Initial testing)

M SD

76.6 8.5

72.5 7.2

13.3 3.2

14.6 3.1

111.0 8.2

113.3 7.7

Years of education

M SD Estimated premorbid I.Q.

M SD

investigators enrolled 152 AD patients in different stages of the disease and 60 normal control subjects in a study of the effects of AD on L-C functions. The purposes of this report are (1) to provide information about the L-C capabilities associated with different stages of AD, (2) to relate the scores of AD patients in different disease stages to those of normal control subjects, (3) to document the variability in L-C test performance of AD patients who are in the same stage of the disease, and (4) to specify the variation in the overall performance profile of AD patients by disease stage. METHOD Subjects One hundred fifty two AD and 60 normal elders participated in the study. All subjects met the following criteria: spoke English as a first language, were literate, had sufficient visual acuity to read newsprint, had no history of drug or alcohol dependency, passed a speech discrimination test with 80% or better accuracy, and had normal intelligence as estimated using demographic information (Wilson, Rosenbaum, & Brown, 1979). All subjects were recruited from the Arizona Health Sciences Center Memory Disorders Clinic, local Alzheimer’s Association support groups, adult day care centers, and referrals from community physicians. Elderly control subjects were spouses of AD patients, members of a senior citizens’ community group, or volunteers at local hospitals. The demographic characteristics of study participants are presented in Table 1.

Diagnosis of Probable AD Diagnosis of probable AD was made according to the NINCDS-ADRDA research task force criteria (McKhann, Drachman, Folstein, Katzman, Price, & Stadlan, 1984). AD subjects had neurological and physical examinations and CT scans. The modified Hachinski scale (Hachinski, Iliff, Zilhka, duBouIay, McAllister, Marshall, Russell, & Symon, 1975; Rosen, Terry, Fuld, Katzman, & Peck, 1980) was used to identify and exclude individuals

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at risk for vascular dementia. Additionally, the Hamilton Rating Scale for Depression (Hamilton, 1960) was completed for mildly demented patients. No subject had a score of 12 or greater, values considered indicative of depression (Lazarus, Newton, Cohler, Lesser, & Schweon, 1987).

Staging of Dementia The Global Deterioration Scale (GDS) (Reisberg, Ferris, de Leon, & Crook, 1982) was used to stage the severity of dementia. An important feature of the GDS is that ratings are generally independent of language function. The GDS defines seven clinical stages, and designation of stage is made after interviewing the patient and family. Patients in stage 1 appear normal. In stage 2 patients are forgetful and in stage 3 patients exhibit the earliest clear-cut clinical deficits. Stage 4 is the late confusional phase. Patients in stage 5 exhibit early dementia, those in stage 6 are in the middle stage of dementia, and those in stage 7 demonstrate late dementia. GDS stages correlate significantly with 13 of the 19 cognitive items in the Inventory of Psychic and Somatic Complaints in the Elderly (Reisberg, Ferris, Schneck, de Leon, Crook, & Gershon, 1981) and with an extensive battery of psychometric measures (Reisberg et al., 1982). Further, significant relationships have been verified between the GDS score and anatomic brain changes seen on computerized tomographic scans (de Leon, Wolf, Farkas, Christman, Reisberg, Fowler, McGregor, Goldman, George, & Rampal, 1980) and metabolic changes as observed through positron emission tomography (Ferris et al., 1980). Additionally, the GDS correlated significantly with CT scan rankings of ventricular dilation and sulcal enlargement (Ferris et al, 1980).

Measures of Linguistic

Communication

Two sets of measures were constructed. The first set, consisting of the Core Linguistic Battery and six additional linguistic and cognitive measures, was administered to mildly and moderately impaired AD patients and normals controls. The second set, the Modified Core Linguistic Battery, was designed for AD patients with severe to very severe cognitive impairment and consisted of a reduced set of stimuli and tasks from the Core Linguistic Battery and two additional oral descriptive discourse tasks. Because this subset of L-C tasks was given to all subjects in the course of the study, it is possible to quantify the L-C performance of subjects from GDS stages 1 through 7.

Core Linguistic

Battery

The core linguistic battery comprised 11 tasks which used the same 13 items from the Boston Naming Test (Kaplan, Goodglass, & Weintraub, 1983): pencil, comb, mask, racquet, harmonica, domino, stethoscope, compass, abacus, tongs, hanger, dart, and knocker. The following tasks were administered in the order in which they are described. Confontarion naming. Subjects were presented with black and white line drawings and asked to name the object. If they failed to name the drawing after 15 set, the real object was presented. One point was awarded for each correct response to either the drawing or the object. Auditory comprehension. Subjects were instructed to select the picture, from among four, representing the object named by the examiner. A point was awarded for each correct response. Writing to dictation. Subjects were asked to write each of the 13 stimulus words spoken by the examiner. Responses were examined for accuracy of spelling, and a point was awarded for each correctly written word. Rending comprehension. This task is the analog to the Auditory Comprehension task,

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differing only in input modality; the input was a written word. Each correct response was awarded one point. Oral reading. Subjects simply read aloud 13 printed words that were each presented on a separate page. Each correctly pronounced word received a score of one point. Concept definition. Subjects were shown a printed word stimulus that they were instructed to define. Definitions were scored according to the criteria used in the Vocabulary Subtest of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) (Wechsler, 1981). For the purposes of this analysis, the WAIS-R scores were halved so that definitions receiving a score of 1 or 2 using the WAIS-R scoring criteria were given the score of 0.5 and 1, respectively. Coordinate naming. When presented with a stimulus object, subjects were asked to name two other objects in the same category. A point was awarded for the item if the subject responded with at least one correct coordinate. Superordinafe naming. When presented with a stimulus object, subjects were asked to specify a larger group of items to which it belonged. For example, when presented with the stimulus object pencil, an appropriate response is writing instrument. Credit was given for any specification of a larger category for the stimulus item. Subjects were not told if their answers were correct. Superordinate iden@cution. In this multiple-choice task, subjects were shown four printed choices that were read aloud by the examiner and asked to select the larger group of things (category) to which the stimulus item belonged. For example, for the stimulus item, harmonica, the four possible choices were: cooking utensil, musical instrument, guitar, and bar of soap. Subjects received one point for each correctly identified superordinate. Pantomime expression. Subject were asked to pantomime the use of pictured objects. If they failed to pantomime to a picture stimulus, the name of the object was spoken by the examiner. Credit was given for any appropriate meaningful gesture in response to either the visual or the auditory stimulus. Pantomime recognition. Subjects were instructed to point to the picture, from among four, that correctly represents the object pantomimed by the examiner. A point was awarded for each correctly identified item.

Additional Language and Cognitive Measures In addition to the aforementioned tasks that used the same 13 stimulus items, six other tasks were administered: Sentence Formulation, Generative Naming, Generative Drawing, Picture Description, Object Description, and the Mini-Mental State Examination. Sentence formulation. Subjects were shown a printed word and asked to generate a sentence containing that word. Six stimulus items were used: harmonica, pencil, compass, stethoscope, abacus, and hanger. A point was awarded for each grammatically correct sentence produced that included the stimulus word. Generative naming. Subjects were asked to name as many words as possible beginning with the letter F in 1 min. Thereafter, they were given a minute in which to name words beginning with A and then S. In this test, developed by Borkowski, Benton, and Spreen (1967), it is unacceptable to give numbers, proper nouns, or different forms of the same word, as in “please” and “pleasing.” One point is awarded for each correct word. Generative drawing. Subjects are asked to draw (without a model) three objects, a triangle, a pail, and a clock. A point was awarded for each correctly represented aspect of the drawn item. Three points were awarded for a correct drawing of a triangle, 7 points for a correct pail, and 12 points for a correct clock. Picture description. Subjects were given the Norman Rockwell Easter Morning picture and asked to described what is happening in the picture. Subjects were allowed 3 min to respond. Subjects’ responses were audiotaped and later transcribed verbatim. A subject’s score was based on the ability to provide five relevant units of information about the setting

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(e.g., characters, time, and place), five relevant units about events (e.g., actions and states), and two relevant units about the main idea of the picture (gist). Thus, a maximum score of 12 could be achieved. Object description. Subjects were given a common object (pencil) and instructed to provide a complete description of the object. Subjects’ responseswere audio recorded and transcribed verbatim. One point was awarded for each new unit of relevant, nonredundant, truthful information provided about the object. Mini-Mental State Examination. The Mini-Mental State Examination (MMSE) (Folstein, Folstein, & McHugh, 1975) is a standard 11-item measure of time, place, and person orientation and general cognitive abilities. The maximum score attainable is 30. A score below 24 is considered abnormal (McHugh & Folstein, 1979).

Modified Core Linguistic Battery for Severely Demented Patients Nine of the stimulus items, that were used in the Core Linguistic Battery, were used in a modified battery that was given to subjects who were unable to do the harder tasks in the core battery such as Coordinate and Superordinate Naming and Definitions. The nine stimulus items were: pencil, comb, hanger, mask, dart, harmonica, knocker, stethoscope, and compass. The modified battery comprised Confrontation Naming, Writing to Dictation, Oral Reading, Pantomime Expression, and Pantomime Recognition. In addition to the Modified Core Linguistic Battery previously described, the Picture Description and Object Description tasks also were given.

Testing Procedures All study participants were tested annually in private in their homes or residential care facility or at the offices of the Aging and Communication Project. All gave informed consent.

Reliability of Scoring and Transcription The scoring of protocols and transcription of taped segments were done by the tester shortly after the test session. Because the scoring of Concept Definition, Superordinate Naming, and Coordinate Naming can involve some subjectivity, interscorer reliability was calculated by having two scorers independently score 10 protocols. Interscorer reliability was defined to be the quotient of the number of agreements divided by the total number of judgments and was calculated to be 97% for Concept Definition, 99% for Coordinate Naming, and 99% for Superordinate Naming. Three tapes also were randomly selected for transcription by the scorers and the reliability of transcription was calculated to be 99%.

Data Analysis Because this study is descriptive in nature, its results do not assume the form of inferential statistics, i.e., there are few formal tests of hypotheses. Presented instead are a variety of illuminating features of large and interesting data set. For each level of GDS, the data from each subject who obtained that level were utilized. Thus, if a subject made a yearly change from GDS 3 to 4 to 5 to 6 to 7 over the 5 years of the study, then that individual would be represented in the descriptive statistics for each of those GDS levels. However, if a subject remained at the same GDS level for more than 1 year, then only that individual’s average scores at that level would be utilizd. Thus, each subject was represented exactly once at each obtained level of the GDS. This strategy suppresses some of the variability within GDS level, but ensures that the variability reported reflects variation between different individuals. It also avoids assigning undue weight to any one subject.

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RESULTS Throughout the results section, two sets of data are reported in relation to each research question of interest in the study. The first data set is the performance of all AD subjects (mild, moderate, and severe) and normal controls on the reduced set of L-C tasks, the Modified Core Linguistic Battery, that were administered regardless of severity of dementia: Confrontation Naming, Writing to Dictation, Oral Reading, Pantomime Expression, Pantomime Recognition. Also administered were the Picture Description and Object Description tasks. The second data set is the performance of only mild and moderate AD subjects and normal controls on the 11 Core Linguistic Battery tasks: Confrontation Naming, Auditory Comprehension, Writing to Dictation, Reading Comprehension, Oral Reading, Concept Definition, Coordinate Naming, Superordinate Naming, Superordinate Indentification, Pantomime Expression, and Pantomime Recognition. The other language and cognitive measures included: Sentence Formulation, Generative Naming, Generative Drawing, and the Mini-Mental State Examination. Mean Scores on L-C Tasks by GDS Stage

In Tables 2a and 2b mean scores and standard deviations are presented for each measure of L-C ability, for each GDS stage. Of primary interest is the tendency across tasks for mean performance to decline as GDS severity increases. The only exceptions to this unsurprising phenomenon are occasional tasks (e.g., Pantomime Expression) for which the mean performance of patients with a GDS of 4 exceeds the mean performance of patients with a GDS of 3. Because the GDS = 3 group is quite small (eight individuals, five of whom received the Pantomime Expression task), these exceptions presumably reflect no more than chance variation. Notice, however, that the pattern of deterioration depends on the task. On the Object Description task, even the GDS = 3 group (very mild AD) is substantially impaired relative to the GDS = 1 group (normal controls); in contrast, performance on the Oral Reading task remains relatively unimpaired in the GDS = 3, 4, 5 groups. Finally, it may be instructive to inquire if the magnitude of impairment observed might be due to chance. This can be investigated by assessing these magnitudes in comparison to the observed standard deviations through classical tests of the null hypothesis that there is no impairment. For cornpairing the GDS = 3 group to the normal control group, this is somewhat problematic because of the small sample sizes involved. At a significance level of (Y = .05, Welch’s approximate t test rejects the null hypothesis only for MMSE, Confrontation Naming (9- and 13-item versions), Auditory Comprehension, Concept Definition, Reading Comprehension, Sentence Formulation, Generative Naming, Picture Description,

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TABLE 2a MEANS AND STANDARD DEVIATIONS OF PERFORMANCEON MODIFIED CORE LINGUISTIC BATTERY (9 STIMULUS ITEMS) AND Two DISCOURSETASKS BY GDS STAGE

GDS stage: n:

Modified Core Battery Confrontation Naming M

SD

1 60

3 8

4 53

5 73

6 77

7 45

8.4 0.8

5.5 1.4

5.6 2.3

3.6 2.5

0.7 1.2

0.0 0.2

8.1 0.8

7.6 0.5

6.3 1.7

4.2 2.5

0.8 1.8

0.1 0.4

9.0 0.1

9.0 0.0

8.7 1.3

7.9 2.2

3.3 3.3

0.1 0.6

9.0 0.1

6.8 2.7

7.8 1.8

4.4 2.8

0.6 1.4

0.0 0.0

8.7 0.7

7.0 1.9

7.0 1.6

4.2 2.5

0.8 1.3

0.0 0.1

8.7 1.9

4.8 2.8

5.5 2.6

3.5 2.0

0.8 1.4

0.0 0.2

18.9 8.3

10.4 4.4

7.6 4.2

3.9 3.5

0.5 0.9

0.0 0.0

Writing to Dictation

M SD Oral Reading

M SD Pantomine Expression

M SD Pantomine Recognition

M SD Discourse Tasks Picture Description

M SD Object Description

M SD

and Object Description. As an extreme example of the difficulties involved, Superordinate Naming exhibits one of the largest group differences, yet that difference is not statistically significant. However, when comparing the GDS = 4 group to the normal group, Welch’s approximate t test decisively rejects the null hypothesis of no impairment (JJ < .OOOS) for all tasks except Oral Reading, for which results are marginal (p = .193 for the 9-item version; p = .058 for the 1Zitem version). Mean Scores of AD Subjects as a Percentage of Normal Control Mean

Because the tasks vary in scale and inherent difficulty, Tables 2a and 2b do not facilitate intertask comparisons. Moreover, the clinical significance of a given score on a task is not immediately apparent. Therefore, Tables 3a and 3b display the means from Tables 2a and 2b as percentages of the normal control mean for the corresponding task. This makes pos-

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TABLE 2b MEANS AND STANDARD DEVIATIONS OF PERFORMANCEON CORELINGUISTICBATTERY(13

STIMULUSITEMS)AND OTHERLANGUAGEAND COGNITIVETASKSBY GDS STAGE GDS stage: II:

1

3 8

4 53

5 67

8.4 1.5

7.9 3.3

5.9 3.4

11.5 0.9

11.4 1.8

9.4 2.8

10.5 1.6

8.8 2.5

6.0 3.5

11.4 1.3

11.6 2.2

9.4 3.3

0.1

12.9 0.4

12.4 2.0

11.6 2.8

10.9 1.5

8.4 1.6

7.5 2.8

4.5 2.5

9.3 2.8

6.0 1.4

3.4 3.6

1.3 2.1

11.8 1.6

6.5 6.4

4.9 4.0

1.6 2.6

12.6 0.4

12.5 0.7

10.0

5.9 4.1

12.9 0.3

9.8 4.1

11.0

12.6 0.9

10.0

5.8 0.4

4.6

60

Core Linguistic Battery Confrontation Naming

M SD

12.1

1.1

Auditory Comprehension

M SD

12.7 0.6

Writing to Dictation

M

11.5

SD

1.1

Reading Comprehension

M SD

12.9 0.7

Oral Reading

M SD

13.0

Concept Definition

M SD Coordinate Naming”

M SD Superordinate Naming”

M SD Superordinate Identification”

M SD

2.5

Pantomine Expression

M SD

2.6

6.5 3.8

9.6 2.2

6.2 3.4

4.4 1.6

2.5 2.0

Pantomime Recognition

M SD

2.6

Other Language and Cognitive Tasks Sentence Formulation

M SD

0.8

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TABLE 2-Continued GDS stage: n: Generative Naming M SD

1 60

3 8

4 53

5 67

41.0 11.2

24.8 8.8

19.1 10.8

8.7 7.8

17.8 2.9

14.8 5.2

11.9 5.2

7.3 5.9

28.8 1.3

21.2 4.0

17.9 4.7

10.8 4.6

Generative Drawing M SD

Mini-Mental State Exam M SD

’ Only two GDS = 3 patients received this task.

sible an evaluation of how far from normal in performance are AD patients in different stages of the disease. For example, patients at GDS = 5 are close to normal (90%) on Oral Reading, far from normal (13-14%) on Superordinate and Coordinate Naming, and approximately 50% of normal on a number of tasks. Percentage of AD Subjects Equal& Normal Control Subjects

or Exceeding the Fifth Percentile of

In Tables 4a and 4b the percentages of scores of AD patients that were at least as great as conservative cutoff score are reported for each GDS group. For each L-C task, the cutoff score was selected to approximate the fifth percentile of the distribution of normal control scores, i.e., approximately 95% of the normal control scores match or exceed the cutoff score. The pattern of declining mean performance with increasing dementia severity is again apparent. Percentage of AD Subjects Obtaining Null Scores

To answer the question of whether a L-C ability is lost, reference can be made to Tables 5a and 5b in which the percentages of null scores are reported for each GDS group. In contrast to the preceding tables, large values in Tables 5a and 5b are associated with diminished performance. The majority of AD patients whose GDS level is 5 or lower are able to get some items correct on the L-C tasks, whereas the majority of AD patients who are at GDS level 6 score 0 on the L-C tasks. Almost no correct responses can be expected from GDS level 7 patients. What emerges from these descriptive analyses is a staging of the deterioration of L-C skills in AD patients by level of dementia severity. On most of the tasks considered in this study, the performance of mildly

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TABLE 3a MEAN PERFORMANCEOF AD SUBJECTS(BY GDS STAGE) INTERPRETEDAS A PERCENTAGEOF THE NORMAL CONTROL MEAN ON THE MODIFIED CORE BATTERY AND Two DISCOURSETASKS

GDS stage: n:

3 8

4 53

5 73

6 77

7 45

Modified Core Battery Confrontation Naming Writing to Dictation Oral Reading Pantomine Expression Pantomine Recognition

65 95 100 76 80

67 78 97 87 80

43 52 89 50 48

8 10 36 7 9

0 1 1 0 0

Discourse Tasks Picture Description Object Description

55 55

63 40

41 21

10 3

0 0

TABLE 3b MEAN PERFORMANCEOF AD SUBJECTS(BY GDS STAGE) INTERPRETEDAS A PERCENTAGEOF THE NORMAL CONTROL MEAN ON THE CORE LINGUISTIC BATTERY AND OTHER LANGUAGE AND COGNITIVE TASKS

GDS stage: i2:

3 8

4 53

5 67

Core Linguistic Battery Confrontation Naming Auditory Comprehension Writing to Dictation Reading Comprehension Oral Reading Concept Definition Coordinate Naming” Superordinate Naming” Superordinate Identification” Pantomime Expression Pantomime Recognition

69 90 91 89 99 77 64 55 99 76 79

65 90 76 90 96 68 37 42 79 85 76

49 74 52 73 90 41 14 13 46 50 49

Other Language and Cognitive Tasks Sentence Formulation Generative Naming Generative Drawing Mini-Mental State Exam

79 60 84 74

75 47 61 62

44 21 41 37

’ Only two GDS = 3 patients received this

task.

demented patients (GDS = 3,4) was greater than 50% of that of normal control subjects. On most L-C tasks, a substantial percentage of AD patients could pass for normal. Rarely did a mildly demented patient obtain a null score with respect to a L-C skill. In contrast, severely demented patients (GDS = 6,7) retained only the

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TABLE 4a PERCENTAGE OF PERFORMANCES EQUALLING OR EXCEEDING A CONSERVATIVE CUTOFF SCORE FOR THE MODIFIED CORE BATTERY AND Two DISCOURSE TASKS BY GDS LEVEL

Cutoff score” Modified Core Battery Confrontation Naming Writing to Dictation Oral Reading Pantomime Expression Pantomime Recognition Discourse Tasks Picture Description Object Description

GDS: tI:

1 60

3 8

4 53

567 73 77

7 6 9 9 8

97 97 95 95 95

25 100 100 40 40

41 69 89 55 45

12 30 63 9 9

0 6 8 0 0

0 0 0 0 0

5 10

97 95

62 62

54 29

29 9

5 0

0 0

45

’ The cutoff score approximates the fifth percentile of the normal control scores. TABLE 4b PERCENTAGE OF PERFORMANCES EQUALLING OR EXCEEDING FOR THE CORE LINGUISTIC BATTERY AND OTHER LANGUAGE LEVEL

Cutoff score”

GDS: ?I:

A CONSERVATIVE CUTOFF SCORE AND COGNITIVE TASKS BY GDS

1 60

3 8

4 53

5 67

Core Linguistic Battery Confrontation Naming Auditory Comprehension Writing to Dictation Reading Comprehension Oral Reading Concept Definition Coordinate Naming Superordinate Naming Superordinate Identification Pantomime Expression Pantomime Recognition

10 11 9 12 12 9 3 8 11 12 11

97 98 95 98 100 95 95 95 100 98 95

25 88 88 57 100 71 100b 50b lOO* 60 60

30 72 62 66 94 37 47 22 48 63 37

14 45 27 39 76 6 19 5 13 12 12

Other Language and Cognitive Tasks Sentence Formulation Generative Naming Generative Drawing Mini-Mental State Examination

5 21 11 27

95 98 96 95

71 62 67 12

49 45 64 0

18 12 16 0

u The cutoff score approximates the fifth percentile of the normal control scores. b Only two GDS = 3 patients received this task.

remnants of a few basic, mechanical L-C skills. Most GDS = 6 patients and virtually all GDS = 7 patients were totally impaired on all L-C tasks. They performed at a very small fraction of the typical normal performance and would virtually never have passed for normal. The

mnst

diversitv

in nerfnrmnnce

was seen in CmS

staue

5 the neriod

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TABLE 5a PERCENTAGEOF NULL PERFORMANCESON THE MODIFIED CORE BATTERY AND Two DISCOURSETASKS BY GDS STAGE

GDS stage: fl:

1 60

3 8

4 53

5 73

6 77

7 45

Modified Core Battery Confrontation Naming Writing to Dictation Oral Reading Pantomime Expression Pantomime Recognition

0 0 0 0 0

0 0 0 0 0

0 2 2 0 0

10 12 5 12 11

58 73 38 72 61

98 98 95 100 98

Discourse Tasks Picture Description Object Description

0 0

0 0

2 2

6 7

56 59

95 100

TABLE 5b PERCENTAGEOF NULL PERFORMANCESON THE CORE LINGUISTIC BATTERY AND OTHER LANGUAGE AND COGNITIVE TASKS BY GDS STAGE

GDS stage: n: Core Linguistic Battery Confrontation Naming Auditory Comprehension Writing to Dictation Reading Comprehension Oral Reading Concept Definition Coordinate Naming Superordinate Naming Superordinate Identification Pantomime Expression Pantomime Recognition

1 60

3 8

4 53

0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 v 0 0 0 0

0 0

Other Language and Cognitive Tasks Sentence Formulation Generative Naming Generative Drawing Mini-Mental State Examination

5 67 4

2 2 2 2 14 16 2 0 0

2 11 2 2 8 40 58 21 9 10

4 2 2 0

24 12 17 0

’ Only two CDS = 3 patients received this task

of moderate dementia. Depending on the L-C task, GDS = 5 performance ranged from small to large percentages of typical normal performance. For many tasks, 10 to 20% of the scores might have passed for normal, whereas comparable percentages were unable to perform certain tasks. Amount and Type of Variation in L-C Performance

A primary objective of this study was to document the systematic deterioration in language and communication skills exhibited by AD pa-

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tients. It is, perhaps, transparent that the dramatic declines reported here are not caused by normal aging; however, to consider the possibility of an age effect, we report the average scores of normal control subjects by age, Tables 6a and 6b. On some tasks, e.g., Oral Reading and Pantomime Expression, no age effect is evident; on other tasks, e.g., Coordinate Naming and Superordinate Naming, performance does appear to decline with age. However, on no task did normal aging reduce performance to the levels observed for even very mild AD patients. The results reported in Tables 2a and 2b beg several questions: first, how much total variation in L-C scores exists within a given GDS level; second, how much of the total variation is due to differences in overall severity; and third, how much of the total variation is due to differences in the relation of one task to another. With regard to the first question, it has already been argued that considerable variation exists within the GDS = 5 group. To answer the second and third questions, it is necessary to decompose total variation into variation due to differences in overall severity and variation due to differences in relative task difficulty. This decomposition was performed for each GDS group on the nine-item Confrontation Naming, Writing to Dictation, Oral Reading, Pantomime Expression, and Pantomime Recognition task scores. These tasks were administered to each group and share a common scale. The total variation in these scores equals the sum of the variances of the five principal components of these variables. A variable that measures variation in the overall level of severity while preserving the typical relations between individual tasks can be constructed as the weighted sum of the task scores, where the ratio of any two task weights equals the corresponding ratio of their mean scores and the sum of the squared weights is unity. The variance of this new variable (the severity within GDS level variable) represents variation in overall severity after controlling for differences in the relation of one task to another. Table 7 presents the information required to answer the three previously posed questions. The third column reports the amount of total variation per 100 observations. The very small amount of variation exhibited by the GDS = 1 and GDS = 7 groups is a consequence of boundary effects: normal subjects (GDS = 1) typically obtain (nearly) perfect scores on these tasks and GDS = 7 AD patients typically obtain null scores. Furthermore, it may be advisable to discount the GDS = 3 row because of the very small number of observations (n = 4) on which it is based. Even so, it seemsclear that mild/moderate AD patients exhibit more variability than do severe AD patients. Of course, this result may simply be an artifact of design differences between these L-C tasks and the GDS. However, to the extent that both are clinically meaningful, it is a finding of practical importance.

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TABLE 6a MEAN PERFORMANCEON THE MODIFIEDCOREBATTERYAND Two DWOURSE TASKS BY NORMAL CONTROL SUBJECTSBY AGE GROUP’

Age group: ?l: Modified Core Battery Confrontation Naming Writing to Dictation Oral Reading Pantomime Expression Pantomime Recognition Discourse Tasks Picture Description Object Description

44 6

65-69 19

70-74 14

75-79 12

380 9

8.6 8.1 9.0 9.0 8.9

8.6 8.2 9.0 9.0 8.9

8.7 8.1 8.9 9.0 8.9

8.5 8.1 9.0 9.0 8.8

7.2 7.7 9.0 8.9 7.9

9.1 17.9

9.1 18.6

8.7 20.4

8.7 19.1

7.4 17.9

a Based on age at initial testing. TABLE 6b MEAN PERFORMANCEON CORE LINGUISTIC BATTERY AND OTHER LANGUAGE AND GXNITIVE TASKS BY NORMAL CONTROL SUBJECTSBY AGE GROUPS

Age group: n:

a.34 6

65-69 19

70-74 14

75-79 12

280 9

Core Linguistic Battery Confrontation Naming Auditory Comprehension Writing to Dictation Reading Comprehension Oral Reading Concept Definition Coordinate Naming Superordinate Naming Superordinate Identification Pantomime Expression Pantomime Recognition

12.7 12.9 11.6 13.0 13.0 11.5 11.6 12.6 12.7 13.0 12.9

12.5 12.9 11.7 13.0 13.0 11.5 10.8 12.4 12.7 13.0 12.8

12.4 12.9 11.6 13.0 12.9 11.0 9.0 11.4 12.7 13.0 12.9

11.7 12.7 11.5 13.0 13.0 10.9 7.7 11.8 12.7 12.9 12.7

10.9 11.8 10.9 12.2 13.0 9.2 7.1 10.2 12.2 12.7 11.4

5.8 44.3 18.1

5.8 41.6 17.9

6.0 40.1 18.0

5.4 33.1 16.2

29.2

29.1

28.7

27.2

Other Language and Cognitive Tasks Sentence Formulation 5.9 Generative Naming 42.9 Generative Drawing 18.3 Mini-Mental State Examination 29.7 a Based on age at initial testing

The fourth column in Table 7 reports the percentages of total variation for which the severity within GDS level variable constructed above can account. That is, these numbers give the proportion of variation that can be explained by differences in overall severity without differences in the

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TABLE I VARIATION IN PERFORMANCEON MODIFIED CORE BATTERY BY GDS STAGE

GDS

n:

Total variation per 100 subjects

Percentage of variation due to differences in overall severity with GDS stage

1 3 4 5 6 I

56 4 42 54 59 41

3.45 191.67 31.57 57.62 33.88 1.83

40.0 39.8 47.7 52.3 71.5 61.8

relative difficulty of the tasks. To the extent that these numbers are substantially greater than zero, they demonstrate variation in global dementia severity not captured by the GDS; to the extent that they are substantially less than 100, they challenge the adequacy of the stage model, which attempts to measure dementia severity in a single dimension. In fact, both of these conditions obtain: the percentages vary between 39 and 72%, suggesting both that the GDS may be insufficiently precise to adequately measure the level of L-C communications skills and that L-C may be sufficiently complicated as to be irreducible to a single measure. Also apparent in the fourth column of Table 7 is a fairly stable tendency for the percentages reported to increase with GDS level. This suggests that, even if the level of overall severity is controlled, the L-C profiles of mild/moderate AD patients are more diverse than those of severe AD patients. This too may be an artifact of test construction; nevertheless, it emphasizes the (clinical) need to adequately measure L-C performance at the lower GDS levels. DISCUSSION Results of this study enable us to provide a profile of L-C abilities of AD patients by stage of disease, identify certain L-C tasks on which mild AD patients perform like normal elders, provide information about the relative difficulty of various L-C processes, specify the stage in the disease in which the greatest change occurs in L-C functions, and provide insight about the degree of variation in L-C performance for individuals at a particular level of dementia severity as measured by the GDS. Profile of L-C Abilities

by Stage of Disease

The mild AD patient with a GDS rating of 3 is forgetful and complains of losing objects and forgetting names. However, objective evidence of memory deficit is apparent only with in-depth interviewing. It is in this stage that the individual is first likely to become lost. In terms of L-C skills, the GDS = 3 individual scores at the 90% or better level of the

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normal mean on Oral Reading, Superordinate Identification, Auditory Comprehension, and Writing to Dictation. However, on the following tasks the GDS = 3 patients is clearly impaired, performing only 55% of the normal mean: Object Description, Picture Description, and Superordinate Naming. Performance on the remainder of the L-C tasks falls between 60 and 90% of the mean of normals. The typical GDS stage 4 patient is in the late confusional stage with obvious cognitive deficits when interviewed. These individuals are still oriented to time and person but have diminished knowledge of recent personal and world events and often use denial as a defense mechanism. They retain the ability to complete simple tasks accurately, have little difficulty traveling to familiar locations, and can distinguish familiar people from strangers. Stage 4 patients still approximate a normal performance on Oral Reading, Reading Comprehension, and Auditory Comprehension tests. Performances on L-C tasks that are typically greater than 50% of the normal mean occur on: Confrontation Naming, Writing to Dictation, Concept Definition, Superordinate Identification, Pantomime Expression, Pantomime Recognition, Sentence Formulation, Drawing, and Picture Description. Measures on which the GDS = 4 patients performance is less than 50% of normal control subjects include: Object Description, Coordinate Naming, Superordinate Naming, Generative Naming, and Object Description. The GDS stage 5 patient is characterized by the authors of the GDS (Reisberg et al., 1982) as having “moderately severe cognitive decline.” They need assistance to survive, are unable to tell their address and telephone number, are disoriented to time and place but retain knowledge of major facts about themselves. GDS stage 5 patients are like normal subjects in performance on only the Oral Reading test and obtain scores that are greater than or equal to 50% of those of normal control subjects on: Auditory Comprehension, Writing to Dictation, Reading Comprehension, and Pantomime Expression. On every other test, their performance is less than 50% of the average performance of normal control subjects. The typical GDS stage 6 patient is unaware of all recent events, retains only sketchy knowledge of the past, may have forgotten the name of family members, and requires substantial assistance with the activities of daily living. Many Stage 6 patients are incontinent. Their performance on L-C tasks does not approximate that of normal control subjects on any test, and on no measure is their performance better than 50% of the normal mean. As might be surmised, the best performance is on Oral Reading which is 37% of the normal mean. GDS stage 7 is late dementia, and patients have very severe cognitive impairment. Patients in this stage typically are incontinent of bowel and bladder, have lost most or all psychomotor skills, and ultimately deteri-

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orate to a state of stupor or coma. Reisberg et al. (1982) report that GDS = 7 patients lose all verbal abilities, and “frequently there is no speech at all” (p. 1138). The results obtained in this study confirm this, with GDS = 7 subjects performing only 1% or less of the normal mean for all language tasks. Tasks on Which Mild AD Patients Perform Like Normal Elders

The Oral Reading task was the one on which mild AD patients were most like normals followed by Superordinate Identification, Writing to Dictation, Auditory Comprehension, and Reading Comprehension. The reader should be cautioned that this is a statement about clinical relevance, not statistical significance. For example, on Superordinate Naming, subjects with GDS = 1 have a mean score of 11.8 vs. those with GDS = 3 who have a mean of 6.5 The difference is clinically important, but not statistically significant because of the very small sample size. The Oral Reading task simply requires subjects to read words aloud but does not measure comprehension. Rather, it tests the integrity of grapheme to phoneme conversion rules, rules that are automatically and unconsciously applied in the normal. Superordinate Identification is also a recognition task in which subjects must select the correct category, from among four, to which a stimulus spoken by the examiner belongs. Like Oral Reading, Writing to Dictation is a mechanical, automatic task that taps the integrity of phoneme to grapheme conversion rules. The Auditory Comprehension task is also a recognition test in which subjects must point to the correct picture, from among four, of the object named by the examiner. In Reading Comprehension, the subject must read a word and identify, from among four choices, the pictorial representation of the word. The preserved ability of mild AD patients to complete these tasks is likely accounted for by the simplicity of their demands. Hasher and Zacks (1979) have demonstrated that among neuropsychological tasks, those that are most effortful are the most difficult. Tasks that require the subjects to recall information, or actively search memory, are recognized as more effortful than those requiring recognition. Relative DifFculty

of Study Tasks

Eleven of the measures administered to subjects in the study used the same 13 stimuli thereby making it possible to compare their relative difficulty for normals and mild AD subjects. The hardest L-C task, as measured by mean performance of the normal control subjects, is specifying the coordinates of an object (Coordinate Naming), that is, providing the names of other objects in the same category as a stimulus object. Next most difficult is the specification of the superordinate (Superordinate Naming), or larger category of things, to which a stimulus object belongs.

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These L-C acts are generative and involve the recall of specific conceptual and linguistic information. As such, among the 11 tasks with stimulus equivalence, they are the most sensitive to mild dementia. The easiest tasks were the previously described Oral Reading and Superordinate Identification tasks, those least sensitive to mild dementia. Stage in Disease When Greatest Change Occurs in L-C Function

The data in Tables 3a-6b document that the greatest decrements in L-C function occur between GDS stage 4 and stage 6. Recall that GDS stage 5 patients are characterized as having “moderately severe cognitive decline” (Reisberg et al., 1982). With the exception of Oral Reading, GDS stage 6 patients had scores on the L-C tasks that were 10% or less of the normal control subjects’ mean scores. Then too, with the exception of Oral Reading, 56% or more of the stage 6 patients score zero on the LC tasks. Variation in L-C Performance by Level of Dementia Severity

For each level of GDS, the total variation in performance on the nineitem versions of five tasks (Confrontation Naming, Writing to Dictation, Oral Reading, Pantomime Expression, Pantomime Recognition) was computed and decomposed into variation due to differences in overall severity and variation due to differences in relative task difficulty. The percentages due to the former fell between 35 and 75, suggesting that there is both (1) considerable variation in overall severity and (2) considerable variation in L-C task profile within each level of GDS. However, total variation for GDS = 7 patients is quite small because these patients typically obtain null scores on all tasks. In summary, the data in this study make it possible to better specify the profile of L-C abilities by stage of disease and level of dementia severity as measured by GDS score. Although the L-C performance of AD patients has been related only to the GDS, the correspondence to other scales is likely very good in so far as they are valid for documenting the stages of Alzheimer’s dementia. The availability of information about L-C performance better prepares clinicians for making the diagnosis of AD, providing prognoses, and counseling patients and caregivers. REFERENCES Appell, J., Kertesz, A., & Fisman, M. 1982. A study of language functioning in Alzheimer’s patients. Brain and Language 17, 73-91. Bayles, K. A. 1982. Language functioning in senile dementia. Brain and Language, 16, 265-280. Bayles, K. A., & Kaszniak, A. W. 1987. Communication and cognition in normal aging and dementia. San Diego: College-Hill Press/Little, Brown. Bayles, K. A., & Tomoeda, C. K. 1991. Caregiver report of prevalence and appearance order of linguistic symptoms in Alzheimer’s patients. The Gerontologht, 31, 210-216.

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