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CAMCOG: Detaileddescription, population dataand psychometric properties


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CAMCOG: Detailed description, population dataand psychometric properties

The Cambridge Cognitive Examination (CAMCOG) is a

concise neuropsychological test for the assessment of

cognitive impairment in elderly people. It was designed

specifically to assist in the diagnosis of dementia at an

early stage. CAMCOG assesses a broad range of cogni-

tive functions, as is required for the diagnosis of demen-

tia, and it minimises floor and ceiling effects by covering

a range of item difficulty.

Aims

To assess the range of cognitive functions required

for a diagnosis of dementia.

To assist in differential diagnosis within the demen-

tias.

To incorporate items which are graded in difficulty

within a cognitive domain in order to assess the full

range of cognitive ability.

To permit the measurement of cognitive decline

from very high levels of premorbid ability by minimiz-

ing ceiling effects.

To facilitate comparison with some other widely

used brief cognitive tests, by including them within

its framework.

To examine profiles of cognitive performance by

deriving scores on subscales which assess different

cognitive abilities.

Content

The items contained in the CAMCOG were selected to

sample the areas of cognitive functioning which arespecified in operational diagnostic criteria, such as those

elaborated in DSM-IV (American Psychiatric Association,

1994) and ICD-10 (World Health Organization, 1993).

These cognitive functions include memory, language,

attention, perception, praxis and thinking (now called

executive functioning). The CAMCOG also samples

important domains within an area of cognitive function-

ing; for example, memory items include assessment of

remote and recent memory, semantic and episodic

memory, intentional and incidental learning, and recall

and recognition measures of retrieval. The CAMCOG

incorporates items which are commonly used in neu-

ropsychological assessment to examine dissociable fun-

tions. Thus, for example, there are measures of language

comprehension and language expression and these are

assessed both in an oral and in a written form. Some

standard neuropsychological items which are included in

the CAMCOG are verbal fluency, similarities and the

identification of objects photographed from unusual

views. A summary of CAMCOG items and subscales is

provided in Table 1.

All the MMSE items are included in the cognitive exami-

nation but the following are not used in calculating the

CAMCOG score; naming two objects (pencil, wrist-

watch), registration and recall of three words, writing a

sentence and paper folding. The processes involved in

these tests are assessed in more detail by other

CAMCOG items. CAMCOG also contains the

Abbreviated Mental Test (AMT) of Hodkinson (1972),

derived from the original Dementia Scale of Blessed

et al. (1968) and its predecessor (Roth & Hopkins,

1953).

CAMCOG-R differs from CAMCOG in three ways:

(1) It includes two additional items to assess executivefunction in more detail; a verbal measure (ideational

fluency) and a non-verbal measure (visual reasoning).

(2) In addition to the six original items assessing remote

memory (for the period of the 1930s and 40s), it

contains six alternative items (for the period of the

1950s and 60s) which are intended for more

recently born cohorts.

(3) The tactile perception item (recognising two coins

placed in the subjects hand) has been omitted.

This item proved problematic as new coins were

introduced and normal elderly people often had dif-

ficulty in recognising them. The omission of this item

brings the CAMCOG total down from the original

107 to the new total of 105.

Scoring

CAMCOG provides subscale scores for hypothetically

dissociable functions, as well as a total score with a

maximum of 105 points. Each item contributes between

1 and 6 points to the relevant subscale and to the total

score. For the animal fluency item, where elderly subjectsmay produce over 40 different animals, recoding is nec-

essary, as specified in question 158.

Despite the addition of further tests of executive func-

tion, the original CAMCOG scoring and total score has


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82 Detailed description

not been changed, but a separate executive function

score may be calculated (see p. 66).

Extended assessment of executive function

CAMCOG takes approximately 20 minutes to adminis-

ter. Strict adherence by the interviewer to the printed

instructions for administration and coding is required to

ensure reliable scores.

Administration

Executive function is the term used to describe a variety

of high level cognitive processes including planning,

organisation, abstraction, categorization, initiation, rea-

soning, mental flexibility, sequencing and the allocation

of attentional resources. Neuropsychological evidence

suggests that the frontal lobes play a key role in perfor-

mance on tasks of executive function (e.g. Cummings,

1993) and that performance on such tasks may be com-

promised relatively early in the course of dementia.

Impaired executive function together with a relative

preservation of memory is indicative of dementia of the

frontal type (e.g. Gregory & Hodges, 1993).

Executive function is very difficult to assess briefly, both

because of the many different processes subsumed

under this rubric, and because most of the existing mea-

sures (many still at an early stage of development) tend

to be time-consuming. The original CAMCOG contains

two items which can be regarded as measures of execu-

tive function. These are the Similarities questions which

assess abstraction, and the fluency item (animals) which

assesses initiation and categorisation. In view of the

increasingly prominent role of executive function mea-

sures in cognitive assessment and dementia diagnosis

two further items have been added. The ideational

fluency item (How many different uses can you think of

Table 1 CAMCOG items and subscales

Subscale Maximum Score Sections Maximum Score

1 Orientation 10 Time 5Place 5

2 Language 30 Comprehension:motor response 4verbal response 3reading 2

Expression:naming 6fluency (animals) 6definitions 6repetition 1writing to dictation 2

3 Memory 27 Remote 6Recent 4New learning: incidental 12New learning: intertional 5

4 Attention and calculation 9 Serial sevens 5Counting backwards 2Calculation 2

5 Praxis 12 Copying 3Drawing 3

Actions to command 66 Abstract thinking 8 Similarities 87 Perception 11 Tactile recognition* 2

Visual recognition 2Unusual views 6Recognise person 1

Total 107

* This item (recognising two coins) has been omitted from CAMCOG-R, changing the total from 107 to 105.


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CAM CO G: Detailed description 83

for a bottle?) is taken from a test battery developed by

Crawford et al. (1995). It assesses initiation and mental

flexibility in the verbal domain. To assess executive func-

tion in subjects who may have language problems, a

non-verbal test of visual reasoning has been added. It

uses a format somewhat similar to Ravens Progressive

Matrices (Raven et al., 1976) and assesses sequencing,

categorisation and abstraction.

The ideational fluency test has been validated in patients

with head injury, where it was found to be more sensitive

to impairment than other fluency tests (Crawford, 1995).

Validation studies are currently underway in normal

elderly and demented patients. The tests are included in

advance of published results, on the basis of their validity

in other contexts and their brevity. They are inserted after

the Similarities items (questions 197200) and num-

bered 200(a) and (b). Because of their provisional status,

scores on these tests do not contribute to the total

CAMCOG score, which remains unchanged. A separate

executive function score may be derived by adding thescores on these two items to the scores on similarities

and animal fluency (see p. 66). For this purpose, both

ideational fluency and animal fluency are recoded, bring-

ing the maximum executive function score to 28.

CAMCOG Applications

CAMCOG has been used in many published investiga-

tions both clinical (e.g. Hunter et al., 1989; Jobst et al.,

1992a, b) and population-based (e.g. OConnor et al.,

1989; Brayne & Calloway, 1990; Clarke et al., 1991;

Cooper et al., 1992). It is currently being used in the UK

in the Medical Research Council Multi-Centre Study of

Cognitive Function and Ageing (MRC CFA Study) and

data will soon be available on over 3000 people aged

65 years and older from a nationally representative

sample, half of whom are being re-assessed annually

with CAMCOG. This study will provide norms on an uns-

elected elderly population as well as data on large

numbers of individuals with dementia.

To date, British norms are available only on a very elderly

cohort in Cambridge City aged over 75 years (Huppert

et al., 1995, 1996). Data from these studies are pre-

sented in Tables 2 and 3.

CAMCOG Profile

For clinical work, it is often useful to have a visual profile of

an individuals cognitive strengths and weaknesses. Jean

Hooper and Romola Bucks, two clinical psychologists

working with older adults in Gloucestershire, have devel-

oped the Cognitive Profile (Hooper & Bucks, 1993)based on CAMCOG subscales, which is scored manually.

A CAMCOG profile can also be obtained using com-

puter scoring and can be printed out from the CAMDEX-

R disk. We are currently developing a computerised

method for examining an individuals obtained versus

expected scores on the CAMCOG total and subscales,

based on his/her sociodemographic characteristics.

Health variables may also be included to examine the

extent to which an individuals cognitive impairment can

Table 2 Performance of an elderly population sample on CAMCOG subscales

Percent obtainingSubscale Maximum value Mean (SD) Median score maximum Range

Orientation 10 9.2 (1.0) 10 51 310Language 30 21.9 (2.6) 25 0 929Memory 27 20.7 (3.6) 21 0 426Attention 7 5.1 (1.9) 5 31 07Praxis 12 10.1 (2.0) 10 27 012Calculation 2 1.8 (0.4) 2 80 02Abstract thinking 8 5.2 (2.3) 5 20 08Perception 10* 7.8 (1.8) 8 16 110Total 106*

* For this community sample one item (recognising two people in the room) had to be omitted, reducing the number of itemsfrom 4 to 3, and the maximum score from 11 to 10. The total CAMCOG score was accordingly reduced from 107 to 106.Source: Huppert et al. (1995)


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be explained by physical disorder or depression as

opposed to dementia (see Jorm, 1994).

Camcog Scores and Sociodemographic variables

CAMCOG scores, like scores on any cognitive test with

an adequate range, are markedly influenced by age, sex,

education and social class. This can be seen in Table 4.

For total CAMCOG score, all four variables exert a sig-

nificant effect even when the other three variables have

been controlled for. For CAMCOG subscales, the rela-

tionship is more complex, with age exerting a significant

effect on almost all subscales while the other variables

show selective effects. These findings make it clear that

sociodemographic variables must be taken into account

when judging whether an individual is impaired or not

impaired compared to the population average.

CAMCOG versus MMSE

CAMCOG examines a wider range of cognitive func-

tions than the MMSE and includes items graded in diffi-

culty. CAMCOG total score is more normally distributed

than MMSE scores (Fig. 1) and avoids ceiling effects.

Figure 2 shows that elderly people who obtain maximum

scores (29 or 30) on the MMSE are widely distributed in

terms of CAMCOG score.

Reliability

Total score on the CAMCOG was found to have excel-

lent internal reliability (Cochrans alpha 0.82, 0.89 in dif-

ferent samples) and testretest reliability (Pearson

correlation 0.86). The reliability of the individual sub-

Table 3 Mean scores of an elderly population sample on CAMCOG subscales

Age Group

7779 8084 8589 90+ All AgesCAMCOG Subscales (n=135) (n=191) (n=64) (n=28)

Orientation 9.5 9.3 8.8 8.9 9.2Language 25.4 25.2 23.5 23.8 24.9Memory 21.7 21.0 18.9 18.6 20.7Attention 5.5 5.1 4.7 4.5 5.1Praxis 10.5 10.3 9.3 8.8 10.1

Calculation 1.8 1.8 1.7 1.6 1.8Abstract thinking 5.6 5.2 4.4 4.6 5.1Perception 8.3 8.1 6.8 6.0 7.8

Source: Huppert et al., (1995)

Figure 1 (a) Distribution of CAMCOG scores(b) Distribution of MMSE scores


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CAM CO G: Detailed description 85

scales, which corresponded to different cognitive abili-

ties, and which may sample qualitatively different

processes, was also acceptable. (Pearson test-retest

reliability 0.460.80). Reliability data are presented in

more detail in Huppert et al. (1996).

CAMCOG and Dementia

CAMCOG scores are very effective in differentiating

between demented and nondemented individuals.

Huppert et al. (1996) report that in an elderly population

sample the CAMCOG total score, as well as each

subscale score, differed significantly between non-

demented individuals and those with the diagnosis of

mild dementia or minimal dementia (Table 5). As well as

differentiating between groups, CAMCOG also differen-

tiates successfully between individuals. CAMCOG total

scores showed high levels of sensitivity and specificity in

differentiating between non-demented individuals and

those with a diagnosis of mild dementia. The cut-point

which produced the highest levels of both sensitivity and

specificity was 80/81, with values of 93% and 87%,

respectively (Table 6). CAMCOG score also predicts

dementia diagnosis. For each 1 point decrease in score,

there is a 20% increase in the probability of dementia

diagnosis.

These findings are described in more detail in Huppert et

al. (1996).

Figure 2 CAMCOG score for high MMSE scorers (29 or 30)

Table 4 Sociodemographic variables and CAMCOG performance

CAMCOG score

No. Female (%) Mean (SD) Median Range

SexMale 137 87.4 (9.5) 90 52102Female 281 67 83.7 (11.5) 86 31102

Age (years)7779 135 64 88.3 (9.1) 89 48102

8084 191 68 86.1 (9.8) 88 551028589 64 67 78.1 (13.3) 81 3110090+ 28 82 76.6 (10.7) 80 5189

Education* (age at leaving school)12/13 52 71 80.0 (12.8) 83 319814 242 64 84.3 (10.2) 86 4810215 52 73 88.0 (10.9) 90 5110216 44 66 87.5 (12.3) 92.5 5210017+ 26 88 90.4 (7.1) 91 67100

Social class*Professional/managerial 82 68 86.1 (10.9) 88 51102Skilled non-manual 74 73 88.2 (10.3) 90 48102Skilled manual 148 62 85.7 (10.1) 87.5 51100Semi-skilled/unskilled manual 103 69 81.4 (12.1) 85 31102

* It was not possible to establish education for 2 respondents, and social class for 1 respondent.Source: Huppert et al. (1995)


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Table 5 Means (and SDs) on Cambridge Cognitive Examination (CAMCOG) and its Subscales as a

Function of Dementia Severity

Non-demented Minimal dementia Mild dementia

Subscale Mean (SD) Mean (SD) Mean (SD)

Orientation** 9.73 (0.57) 9.03 (0.96) 7.19 (1.83)

Language** 26.13 (2.27) 24.01 (2.20) 22.16 (3.75)Comprehension** 8.66 (0.63) 8.33 (0.82) 7.67 (1.34)Expression* 17.44 (2.00) 15.68 (1.83) 14.58 (2.83)

Memory** 22.18 (2.67) 18.41 (4.20) 14.74 (4.55)Remote Memory** 4.75 (1.21) 3.97 (1.44) 2.94 (1.47)Recent Memory** 3.82 (0.46) 3.37 (0.85) 2.23 (1.23)Learning** 13.56 (1.88) 11.09 (3.04) 9.30 (3.55)

Attention/Calculation* 6.91 (2.14) 5.16 (2.38) 4.32 (2.37)

Praxis** 1.57 (1.64) 9.40 (1.90) 8.10 (2.11)

Abstract Thinking** 5.78 (2.13) 4.64 (2.41) 2.58 (2.15)

Perception* 7.87 (1.80) 6.89 (1.88) 6.20 (1.53)

CAMCOG** 89.69 (8.49) 77.95 (9.72) 65.46 (1.69)

Note: Because of missing data, n = 291322 for non-demented, 6471 for minimal dementia and 4153 for mild dementia.

** All group means differ, P

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