Assessment of cognitive impairment and dementia using informant reports

Clinical PsychologyReview,Vol. 16, No. 1, pp. 51-73, 1996 Copyright 0 1996ElamierScience Ltd Printed in the USA. All rights reserved 0272-7xX3/96 $15.00t .oa

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ASSESSMENT OF COGNITIVE IMPAIRMENT AND DEMENTIA USING INFORMANT REPORTS A. E jorm NH&MRC Social Psychiatry Research Unit, The Australian National University

ABSTRACT. When assessing cognitive impairment and dementia, clinicians ojen seek infomationfim informants to comj&ment thefindingsjvm cognitive tests. In recent years, a number of standardized methods have been &eloped for collectinginfDnnant data, but these are not widely known. Them are several advantages of using these metM including: ewer$uy reb Vance, acceptability, useability with nor&stable subjects, administration by tele@wne or mail, potential longitudinal perspective, and greater cnxs-cultural jmrtability. This review identified 12 scales measuring cognitive impairment as a continuum, and fmr instruments for diagnosing dementia on the basis of infonrurnt data. Research on the psychometric properties of these instruments is reviewed. It is concluded that inf~ntbased measures tap a global factor of cognitive im@ment, are highly reliable, correlate with cognitive tests, and discriminate demented jvm mmdemented subjects. Non-cognitivefactors and informant characteristics are also likely to influence informants’ ratings, but less is known about these influences. Although informantbased methods are a comparatively recent development, existingfindings su#ort their use as a complement to cognitive testing particularly in assessment of dementia.

THERE ARE several kinds of approaches which clinicians can use to assess cognitive impairment in their patients: cognitive testing, self-report of cognitive deficits by the patient, observation of everyday performance by staff, and informant reports of everyday cognitive functioning. Cognitive testing has been the dominant approach to assessment, involving both detailed cognitive tests such as the Wechsler scales (Wechsler, 1981; Wechsler 8c Stone, 1987) and brief screening tests such as the Mini-Mental State Examination (MMSE; Folstein, Folstein, & McHugh, 1975). This approach is supported by extensive data on the reliability and validity of cognitive tests. Nevertheless, there has been some disquiet

Correspondence should be addressed to A. F. Jorm, NH&MRC Social Psychiatry Research Unit, The Australian National University, Canberra 0200, Australia. 51

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about the real-life relevance of many cognitive tests (e.g., Poon, Rubin, dcWilson, 1989; Sunderland, Harris, & Baddeley, 1983). This disquiet has led to the development of tests with greater everyday relevance, as well as the investigation of alternatives such as self-report of cognitive functioning. Self-reports are extensively used in other areas of psychological assessment such as personality testing, so their extension to cognitive assessment would seem reasonable. However, while there is good evidence for the reliability of self-reports, validity has been poor (e.g., Herrmann, 1982; Jorm, Christensen et al., 1994; O’Connor, Pollitt, Roth, Brook, & Reiss, 1990; O’Hara, Hinrichs, Kohout, Wallace, & Lemke, 1986; Sunderland et al., 1983). Several studies have found that self-reports of cognitive deficits are related more to depression than to performance on cognitive tests (Bolla, Lindgren, Bonaccorsy, & Bleecker, 1991; Jot-m, Christensen et al., 1994; Kahn, Zarit, Hilbert, & Niederehe, 1975; McGlone et al., 1990; O’Connor et al., 1990; O’Hara et al., 1986). A likely reason for the poor validity of self-reports is that patients who are cognitively impaired are unlikely to correctly recall and evaluate their own cognitive failures. Because of these limitations, other approaches are needed to provide an assessment of everyday cognitive functioning. Two promising approaches are observation of everyday behavior by staff and reports from an informant, usually a close relative. StaE observation has been harnessed in psychogeriatric rating scales, such as the Inpatient Memory Impairment Scale (Knight & Godfrey, 1984), which specifically assesses cognitive functioning and multidimensional instruments such as the London Psychogeriatric Rating Scale (Hersch, Kral, & Palmer, 1978) which assess several domains of functioning. Such instruments are most relevant to patients in hospital or other residential care facilities and are often filled out by nurses. Staff rating scales are less relevant to patients living in the community. For communitydwelling subjects, informants’ reports are a valuable complement to cognitive testing. Although it is routine in clinical practice to interview an informant and gather historical information, this approach lacks the extensive psychometric development that has gone into cognitive tests. The purpose of this review is to give an overview of quantitative methods of assessing adult cognitive deficits or dementia using reports from informants. Although a sizeable body of research has been carried out on informant-based methods during the 1980s and 199Os, this work is not widely known and has not previously been drawn together. The research has been published in journals from a variety of disciplines (psychology, psychiatry, neurology, gerontology, and geriatrics) and there is comparatively little cross-citation in the literature. ADVANTAGES

AND LIMITATIONS

OF INFORMANT-BASED

ASSESSMENT

Several advantages have been claimed for informant-based assessment over traditional cognitive testing: l

Everyday reham. As mentioned above, an advantage of informant-based assess ment is that it taps everyday cognitive performance. Performance in everyday lie is determined not only by cognitive abilities, but by the demands imposed by the person’s environment (Sunderland, Watts, Baddeley, 8c Harris, 1986). A person living a restricted life will require a lower level of ability to function adequately than a person with an intellectually demanding life. Informant-based assessment is more likely to tap the fit between the person’s ability and the environment’s cognitive demands than is cognitive testing which relies on a standard set of artificial tasks.

Assessment Using Informants

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Acceptability. For some people, cognitive testing is an unpleasant experience because it draws attention to their deficits (Jot-m, Henderson et al., 1994). By contrast, informant-based assessment does not require the direct participation of the person being assessed. It may be used to gather data on people who do not wish to undergo cognitive testing. However, this advantage must be balanced against the ethical issue of informed consent. Possibb with nontestable patients. Severely cognitively impaired patients may not be assessable at all with cognitive tests. Informant-based assessment is not constrained by patient impairment, provided that the items used include some which discriminate among the severely impaired. Informant-based assessment can even be carried out retrospectively after the patient has died (Davis, White, Price, M&eel, Jc Robins, 1991; Thomas et al., 1994), which can be valuable for researchers examining neuropathological correlates of cognitive impairment. Mail or telephone administration. Informant-based assessment does not require facetoface contact with the informant. Assessment has been carried out by mail (Jorm & Jacomb, 1989; Kukull & Larson, 1989; Sunderland, Harris, & Gleave, 1984) and by telephone &was, &gal, Stewart, Corrada, & Thal, 1994). Longitudinal perspective. In some circumstances, it is desirable to measure change in cognitive functioning over time. Measurement of change requires two or more measurement points, but often only an assessment of current functioning is available. However, informants can use their knowledge of the subject’s functioning earlier in life to directly rate change in performance. Cross-cultural portability. With cognitive tests, comparisons across cultural groups are difficult even with “culture-fair” tests. These tests are based on artificial tasks which will vary in their familiarity across cultures. With informant-based assessment, it may be possible to ask about aspects of everyday life which are common to many cultures (e.g., remembering people’s names). Although little research has been done on the problem of cross-cultural portability using informant-based assessment, the early results look promising (Hall, Hendrie, Brittain, & Norton, 1993). Because informants can rate change from earlier in life, informant-based assessment may also be less affected by education, making it applicable to a range of socioeconomic groups (see below). Some Zimitationr. The major limitation is that patients will sometimes lack a suitable informant, particularly if a longitudinal perspective is required (Ritchie 8c Fuhrer, 1992). A second limitation is a more theoretical one. Cognitive tests use artificial tasks to try to assess specific cognitive abilities, such as episodic memory and spatial reasoning. By contrast, everyday cognitive tasks covered by informant assessments are more complex and may involve many specific abilities. The informant approach will therefore not be useful in situations where specific cognitive functions need to be assessed (Jorm, 1992). INFORMANT-BASED

INSTRUMENTS

FOR COGNITIVE

ASSESSMENT

There are three types of assessment instruments which are informant-based: brief measures, often consisting of a single question, which classify individuals as cognitively impaired or not; multiple-item scales measuring a continuum of cognitive impairment; and instruments which attempt to make a diagnosis of dementia solely using informant data. These various instruments are described below and data on their validity are reviewed. Reliability data have been summarized in Table 1.

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TABLE

1. Reliability

of Informant 3nstruments Type of Reliability

Instrument

Internal

Brief measures

Test-Retest

Interinformant

.64 to .71

Scales

Relatives’ Questionnaire GERRI CBRS IQCODE

PFQ

MOQ2 DECO Short MQ PAS Diagnostic measures= DQ: dementia DQ Alzheimer’s dementia

.95 .95 .84 .93 .80 .71 .97 .85 .78

.51 (1 week) .96 to to to to

.92 .97 .88 .92

to .89

.61 to .86 (1 week) .96 (days), .75 (1 year) .62 to .82 (months) .92 (2 weeks) .93, .94 (days) .97 (l-4 years) .95 (l-4 years)

.92, 1.0 60, .78

Note. Abbreviations and references for data are: Brief measures (Jorm, Christensen et al., 1994) ; Relatives’ Questionnaire (Sunderland et al., 1986; Taylor, 1990); GERRI = Geriatric Evaluation by Relatives Rating Instrument (Schwartz, 1983); CBRS = Cognitive Behavior Rating Scale (Williams et al., 1986); IQCODE = Informant Questionnaire on Cognitive Decline in the Elderly (Fuh et al., 1995; Jorm &J acomb, 1989; Jorm et al., 1989,199l; Morales et al., 1995); PFQ = Present Functioning Questionnaire (Crockett et al., 1989); MOQ2 = Memory Observation Questionnaire 2 (McGlone & Wands, 1991); DECO = Deterioration Cognitive Observee (Ritchie & Fuhrer, 1994); Short MQ= Short-Memory Questionnaire (Koss et al., 1993); PAS = Psychogeriatric Assessment Scales (J orm, Mackinnon et al., 1995); DQ = Dementia Questionnaire (Silverman et al., 1986, 1989). %appa coefficients.

Brief Measures Brief informant-based

measures have been used in two epidemiological

community

sur-

veys (Grut et al., 1993; Jorm, Christensen et al., 1994) and in a clinical study (van der

Cammen, van Harskamp, Stronks, Passchier, & Schudel, 1992). In the survey by Grut et al., each informant was asked “if he/she found the memory of the subject to be impaired.” The informant had three alternatives to choose from: Unchunged Someimpairment, or Considerableimpairment. The informants’ ratings correlated .60 with both MMSE scores and a clinician’s assessment of dementia severity, supporting their validity. In the survey by Jorm, Christensen et al. (1994), informants were asked questions about memory and intellectual decline in the subjects. The memory question was: “In your opinion does X remember things as well as s/he used to? That is, is her/his memory the same as earlier in life.?” If the informant said no, they were asked a sub sidiary question: “Does this interfere with her/his day to day life?” A similar question was asked about intellectual decline: “In your opinion can X think and reason as clearly as earlier in life?” and “Does this interfere in any way with her/his day to day life?” An indicator of validity is the correlation of these questions with the MMSE and other cognitive tasks. For the MMSE, the correlations ranged from .12 to .30, and there

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were correlations of similar magnitude for the other cognitive tests. These correlations are lower than those reported by Grut et al. (1993), probably because the sample contained a much smaller proportion of dementia cases. The study by van der Cammen et al. (1992) was carried out in a geriatric outpatient clinic. A geriatrician asked informants “whether they had observed structural memory problems or behavioural evidence of memory dysfunction in the patient’s everyday performance during the past three to six months.” Furthermore, it was explained to informants that “incidents of memory dysfunction should have occurred repeatedly and should indicate a change or decline from a previous level of functioning.” The informant’s answer was recorded as yes or no. These researchers found that the group reported to have memory problems was clearly lower on the MMSE than the negative group. Furthermore, the informants’ reports agreed more strongly with a consensus clinical diagnosis of dementia than did the MMSE. The sensitivity (true positive rate) of the informants’ reports was 97% and specificity (true negative rate) was 82%. In conclusion, the brief measures perform reasonably in samples with a high proportion of dementia cases. However, they are best seen as indicators of cognitive impairment for groups of individuals, rather than as suitable for individual assessment. Scales There are 12 scales which have been developed to gather information from informants on cognitive functioning. Some of these scales form part of broader instruments which measure areas of functioning other than cognition. The scales are reviewed below in historical order. Blessed Demenh SC&. Blessed, Tomlinson, and Roth (1968) appear to have been the first to develop an informant-based scale of cognitive impairment. They developed this scale for a study of the relationship between Alzheimer pathology and degree of dementia. The scale consists of three sections, covering everyday cognitive changes, changes in activities of daily living (eating, dressing, toileting) and changes in personality. The items do not give the actual questions to be asked of an informant; rather, the scale lists behaviors for a clinician to question the relative about (e.g., “Tendency to dwell on the past”). The clinician then has to rate the patient on each item. Despite the different content of the three sections of the scale, the items are added together to give a single score. Blessed et al. (1968) found that this dementia score correlated highly with plaque count at autopsy (r = .77). However, no separate data were presented on the cognitive items of the scale. Later research with the Blessed Dementia Scale has similarly used the total score, despite the diversity of behaviors it encompasses. An exception is a study by Erkinjuntti, Hokkanen, Sulkava, and Palo (1988). They found that the Blessed Dementia Scale performed better as a screening test for dementia if the personality change items were omitted. They also found that each of the cognitive items clearly discriminated demented patients from controls, supporting their validity. Today the Blessed Dementia Scale is mainly of historical interest because better choices are available. Its disadvantages are that it adds together cognitive and noncognitive items and some of the items are difficult to interpret. R&ztives @e.&nmu& The Relatives’ Questionnaire consists of 35 items dealing with everyday memory functioning (Sunderland et al., 1983). There is a parallel Patients’ Questionnaire for collecting data on self-reported memory problems. In its original

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form, the Relatives’ Questionnaire was designed to be administered by interview. Each item was rated according to frequency of occurrence over the past few weeks on a 5point rating scale ranging from Never to SeueruZtimes a day. (A small subset of the items was rated on a different scale from Never to On euery occ&m.) In later research, the Relatives’ Questionnaire was modified to a 28item version which could be administered by mail (Sunderland et al., 1984). In this revised questionnaire, items were rated on an Qpoint scale ranging from Not at all in the past 3 months to More than me a day. A different questionnaire was also developed by Taylor (1990)) but this was largely based on the Sunderland et al. (1983) questionnaire. The Relatives’ Questionnaire (or one of its variants) has been used with head injured patients (Sunderland et al., 1983, 1984), stroke patients (Lincoln & Tinson, 1989)) multiple sclerosis patients (Taylor, 1990), and normal elderly subjects (Sunderland et al., 1986). The factor structure of the Relatives’ Questionnaire has been studied by Sunderland et al. (1984) using principal components analysis. They found a single factor accounting for 60% of the variance in one group of head injured patients and 51% in another. Sunderland et al. (1983) tried multidimensional scaling and cluster analysis with the items, but no clear clusters emerged, adding further support for a single factor. Correlations of the Relatives’ Questionnaire with the corresponding Patients’ Questionnaire have varied widely. Sunderland et al. (1983) found correlations ranging from .09 to .58, with higher correlations for head injured groups than normals. Sunderland et al. (1986) found a correlation of .35 with elderly subjects, and Taylor (1990) reported a correlation of .72 with multiple sclerosis patients. Lincoln and Tinson (1989) reported a correlation of .72 with stroke patients. To assess its validity, several studies have correlated the Relatives’ Questionnaire with memory and other cognitive tests. Sunderland et al. (1983) found widely varying correlations from test to test and for different subject groups. The highest correlations were with a test of story recall (rs of -.lO, .41, and .72). In their later study with elderly subjects, Sunderland et al. (1986) found smaller correlations, but again the highest was with story recall (r = .26). Taylor (1990) found a correlation of .50 with a battery of cognitive tests; Lincoln and Tinson (1989) found a correlation of .46 with the Rivermead Behavioural Memory Test (Wilson, Cockburn, Baddeley, & Hiorns, 1989) and somewhat lower correlations with other memory tests (rs ranging from .lO to .31). A further measure of validity is the correlation with diary measures of memory failures. Sunderland et al. (1983) had informants complete a checklist of memory failures every evening for 7 days. Depending on the particular subject group, the frequency of recorded memory failures correlated from .53 to .68 with the Relatives’ Questionnaire. A final indicator of validity is the ability to discriminate between patient groups and normals. Sunderland et al. (1983) found that head injured groups had higher scores on the Relatives’ Questionnaire than a normal group. Consistent with this, Sunderland et al. (1984) found that severely head injured patients tended to have higher scores than mildly head injured patients. Geriatric Emdmtion by Rdatives Zbting Znstrument (GEZWZ). The GERRI aims to measure three domains of functioning in elderly people: Cognitive Functioning, Social Functioning, and Mood. Only the Cognitive Functioning scale is relevant here. This scale consists of 20 items which relatives rate on a live-point scale ranging from I. Almost all the time to 5. Almost never. Schwartz (1983) developed the scale using the relatives of 45 demented patients, with two relatives rating each patient. The scale was

Assessment UsingInfants

57

found to discriminate patients diagnosed with different levels of dementia severity, supporting its validity, but the magnitude of the correlation was not reported. Factor analysis of the items was not possible because of the small number of patients, but the three scales comprising the GERRI were found to be highly inter-correlated, suggesting the existence of a general factor. The Cognitive Functioning scale correlated 88 or .89 with Social Functioning (depending on whether the first or second informant was used) and .43 or .55 with Mood. In the only other study with the GERRI, Rozenbilds, Goldney, Gilchrist, Martin, and Connelly (1986) used it with 51 elderly psychiatric patients. They found the Cognitive Functioning scale correlated .54 with a nurses’ rating scale of cognitive functioning and -59 with the MMSE. These correlations also support the validity of the Cognitive Functioning scale. Cambridge Mentul Disorders of the Elderly l&umination (CAMD~). The CAMDEX is a structured psychiatric examination incorporating a mental status examination and cognitive testing of the subject and an interview with an informant (Roth et al., 1986). The informant interview asks about functioning in a range of areas: memory, orientation, general intellectual functioning, activities of daily living, personality, behavior, and mood. Only the two items covering memory and the three covering orientation are relevant here. Each item is rated as 0. No difficulty n&d, 1. Slight dijjiculty, or 2. G-eat difficulty Using data from an epidemiological survey of dementia, O’Connor, Pollitt, Brook, and Reiss (1989) gave the full CAMDEX and derived subscores for memory and orientation from the informant interview. The informant memory score was found to correlate .67 with memory test items and the informant orientation score was found to correlate .61 with orientation test items. These high correlations support the validity of the informant scales. The correlation between the two informant subscores was not reported, so it is not known whether they were tapping different constructs. Although the CAMDEX has been used in other studies, data on the informant cognitive questions have not been reported separately. However, one notable study explored the feasibility of a method for general practitioners to detect dementia in their elderly patients (O’Connor et al., 1993). General practitioners were trained to use the Information/Orientation test (Pattie dc Gilleard, 1976) to screen for dementia and then to follow up any positive cases with an informant interview based on the CAMDEX. This study found that the informant interview added useful information to the cognitive screening test and was well accepted by both general practitioners and informants. Cognitive Behavior Rating scale (CBZE). The CBRS (Williams, 1987) consists of 116 items divided into nine subscales: Language Deficit, Apraxia, Disorientation, Higher Cognitive Deficits, Memory Disorder, Dementia, Agitation, Need for Routine and Depression. The first five of these involve the assessment of cognitive functioning. Items are rated from 1. Not at all l&e thG@rwm to 5. Verymuch like this person. The CBRS is designed for selfcompletion by the informant and takes 15-20 minutes. The grouping of the CBRS items into subscales was validated through expertjudgement (Williams, Klein, Little, & Haban, 1986). Ten neuropsychologists were asked to group the items into predetermined categories. Only those items which were grouped consistently by at least eight of the neuropsychologists were retained in the final version of the CBRS. Validity of the CBRS was assessed using a sample of 30 Alzheimer’s dementia cases and 30 matched controls, and a sample of 400 normals recruited through

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advertisements (Williams et al., 1986). Each subscale discriminated the Alzheimer’s dementia group from the normal controls. However, the correlations among the subscales have not been reported. Williams (1987) reported normative data on the CBS derived from a sample of 688 normal volunteers recruited via advertisements. Although the ages ranged from 39-89 years, no age differences were found on any of the cognitive subscales. The norms can be used to derive a profile based on percentile ranks or standard scores (with a mean of 100 and standard deviation of 15). Zt+zamt Qtmhmak 011 CognitiveDe&m?in theHdkdy (Z@ODE). The IQCODE is a 26item questionnaire which asks the informant about cognitive changes over the previous 10 years. In its current version, items are rated on a 5-point scale from I. M&a imjnwed to 5. Much woTse(Jorm, 1994). The IQCODE differed from previous informant scales in attempting to measure change rather than current functioning. The aim was to produce a measure which was not influenced by education and premorbid ability, in contrast to cognitive screening tests such as the MMSE which reflect both premorbid ability and decline. The period of 10 years was chosen as the time base because of epidemiological evidence that the time from onset of dementia to death is generally less than this. The IQCODE was originally developed as an informant interview (Jorm 8c Korten, 1988). A pool of 39 items was administered to an elderly sample and reduced to 26 items on the basis of item-total correlations. The 26item scale was found to correlate highly with the MMSE (r= .74), but had lower correlations than the MMSE with indicators of premorbid ability like education and word reading ability. In subsequent work, the IQCODE was presented as a self-administered questionnaire which could be completed by mail if necessary. Norms from an elderly Australian general population sample have been reported byJot-m and Jacomb (1989) and can be used to derive percentile ranks. Principal components analysis of the IQCODE items in three samples have shown a single large factor accounting for SO%, 42%, and 48% of the variance respectively (Fuh et al., 1995; Jorm & Jacomb, 1989; Jorm, Scott, 8c Jacomb, 1989). Although Morales, Gonzalez-Montalvo, Bermejo, and Del&x (1995) have reported two oblique factors, these were correlated .52. This large general factor has emerged even though the original sampling of items for the IQCODE was designed to cover a broad range of cognitive functions. Several studies have been carried out on its validity, using both general population and clinical samples. Because the IQCODE purports to measure cognitive change, it should have correlations with cognitive tests which measure current cognitive functioning, but be uncorrelated with indicators of premorbid ability. Correlations with the MMSE have been assessed in seven different samples and ranged from .37 to .78, with a mean of .59 (Bowers, Jorm, Henderson, & Harris, 1990; Christensen & Jorm, 1992; Fuh et al., 1995; Jorm, 1994; Jorm et al., 1989; J orm, Scott, Cullen, & Makinnon, 1991; Jorm, Broe et al., in press). Other correlations are .78 with the Information/Orientation test (Bowers et al., 1990) and .65 with a test of episodic memory (Jorm, 1992). Jorm, Broe et al. (in press) reported correlations with a battery of neuropsychological tests, with most correlations in the range of .2 to .4. The highest correlations were with story recall (r = .42), recognition memory for words (r = .44) and choice reaction time (r = .40). The IQCODE also appears to be uncontaminated by premorbid ability. Correlations with education have all been near zero (Christensen & Jorm, 1992; Jorm, 1994; Jorm et al., 1989; Jorm & Jacomb, 1989). Across four samples, the aver-

Assessment Using Informants

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age correlation with the National Adult Reading Test (NART, Nelson, 1982) has been .lO, compared to an average correlation of .43 between the MMSE and the NART (Christensen & Jorm, 1992; Jorm, 1994; Jorm et al., 1991; Jot-m, Broe et al., in press). Other studies have assessed the validity of the IQCODE as a screening test for dementia. Bowers et al. (1999) asked general practitioners to rate the degree of dementia in their patients on a scale from Not at aU to Severeand found that these ratings correlated .65 with the IQCODE score. Jon-n and Jacomb (1989) found that the scale distinguished a dementing sample from a general population sample with clearly separated frequency distributions. Three later studies compared the IQCODE with the MMSE as a screening test for dementia using receiver operating characteristic (ROC) analysis (Hanley & McNeil, 1982). A general index of test performance is given by the area under the ROC which can vary from .5 (chance performance) to 1.0 (perfect performance). Out of seven comparisons using various diagnostic standards, the difference in performance between the two tests was statistically significant in only one instance and in that case it favored the IQCODE (Jorm, 1994; Jot-m et al., 1991; Jot-m, Broe et al., in press). Correlations with depression and anxiety scales have been reported in two studies. In the first study, the correlations were low (r = .14 with depression and .lO with anxiety; Jorm, 1994), while in the other study they were much higher (r = .45 and .38, respectively; Jorm, Broe et al., in press), probably because of the greater prevalence of symptoms in the latter sample. Two other forms of the IQCODE have been developed. Jorm (1994) reported a short 16-item version which performs equally to the long form as a screening test for dementia (Jot-m, 1994; Jot-m, Broe et al., in press). There is a retrospective form of the IQCODE which has been developed for assessing deceased subjects (Jot-m, 1990; Thomas et al., 1994). The IQCODE has also been translated into languages other than English. In a Spanish study, the IQCODE was found to perform better than the MMSE as a screening test for dementia and not to have significant correlations with schooling and premorbid intelligence (Morales et al., 1995). Similar findings emerged in a Chinese study (Fuh et al., 1995). The IQCODE performed better than the MMSE as a screening test for dementia and had no correlation with education. The lack of correlation with education is particularly interesting because this sample included subjects with no formal education. Preliminary data have also been reported on the use of the IQCODE with Japanese Americans (White et al., 1994). These studies show that the IQCODE can be valid in cultures different from the one where it was developed. F+~~entFunctioning win? (Pw. The PFQ is a structured interview covering five domains: memory, language skills, everyday tasks, personality, and self-care (Crockett, Tuokko, Koch, & Parks, 1989). Only the first three of these are relevant to cognitive assessment. Each item in the PFQ consists of a problem which is rated as present or absent (e.g., “Problems maintaining a train of thought”). The validity of the PFQ has been investigated using 70 normal elderly volunteers and 348 referrals for investigation at an Alzheimer’s disease clinic. All three cognitive scales were found to differentiate the normals from the suspected dementia cases, although sensitivity and specificity were not reported. There were also small correlations with education (range of r= .14 to .23), indicating some influence of premorbid ability. All PFQscales were found to be intercorrelated, indicating the presence of a general factor of cognitive functioning.

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Memavy Observation w 2 (MOQ2). The MOQ2 is a slightly shortened version of an earlier scale, the MOQ. It has both self-report and informant-report versions (McGlone et al., 1999). There are also two parts to the informant questionnaire: the MOQ2-RA which asks about current memory functioning, and the MOQ2-RB which asks about change in memory over the last several months. The time base for rating change is much shorter for the MOQ2-RB than for any other informant scale, The MOQ2-RA consists of 22 questions which are answered as true or false, while the MOQ2RB has 27 questions rated on a 5point scale ranging from Much worse to Much bet&r. The psychometric data collected for the development of the MOQ have not been published, although McGlone and Wands (1991) cite some of these data. Published data on the validity of the MOQ2 come from a study comparing demented patients with memory complainers and normals (McGlone et al., 1990), and two studies of temporal lobectomy patients (McGlone 8c Wands, 1991; McGlone, 1994). A low correlation of .06 has been reported between the two informant scales (McGlone &Wands, 1991), which is perhaps not surprising given that the MOQZ-RB purports to measure change over a very brief period. Correlations with the corresponding self-report scales were reported to be nonsignificant in a study of memory complainers (McGlone et al., 1990), but positive correlations were later reported with temporal lobectomy patients (r = .23 for forms RA with SA, r = .63 for forms RB with SB) (McGlone &Wands 1991). Validity has been examined by comparing patients with normals. McGlone et al. (1990) found that both informant scales discriminated a dementing group from a control group, but were not as good at discriminating memory complainers from the other two groups. McGlone and Wands (1991) found that both informant scales discriminated between temporal lobectomy patients preoperation, a separate group of postoperation patients and normal controls. However, a later longitudinal study of temporal lobectomy patients, who were compared pre- and post-operation, found only a nonsignificant trend in the same direction (McGlone, 1994). Other evidence of validity comes from correlations with cognitive tests. McGlone et al. (1990) reported a principal components analysis of the four MOQ2 scales, a depression scale and a memory test. The self-report forms loaded on one factor along with depression, while the informant scales loaded on a second factor with the memory test. McGlone (1994) reported correlations with the Wechsler Memory Scale (Wechsler & Stone, 1987) and a test of nonverbal memory in temporal lobectomy patients before and after the operation. Form RA (current performance) had correlations with the Wechsler scale (r = .50 and .36), but not with the nonverbal test ( r= -. 11 and .18). By contrast, form RB (assessing change) had near zero correlations with the Wechsler scale (r = .lO and .06) and inconsistent correlations with the nonverbal test (r = -40 and -.04). These apparently inconsistent results may have had something to do with the small sample size involved (N= 22). D&&ioru&m Cognitive Obsenke (DECO). As its name suggests, the DECO was developed in French, but there is an English translation available. It is a 19-item questionnaire developed as a screening test for dementia in which the informant rates cognitive change over the past year (Ritchie & Fuhrer, 1992). Items are rated as Better ur about the same, Not as well, or Much worse. The time period of a year was chosen because of difficulties in finding informants who had known subjects over a longer period of time. The authors acknowledge that this time base may limit the usefulness of the DECO with severely demented patients who have reached a plateau of functioning.

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The validity of the DECO as a screening test has been evaluated using ROC analysis in a study of 120 persons with mild or moderate dementia compared to 155 normal elderly controls (Ritchie & Fuhrer, 1992). The DECO’s performance as a screening test was compared with that of the MMSE and the Iowa Test (a brief neuropsychological examination). The DECO was found to perform extremely well, with an area under the ROC of .94. Although the DECO did not perform significantly better than either the MMSE or the Iowa Test, it was better at distinguishing mild dementia. To see if the performance of the tests was affected by education, the ROC analysis was repeated for high- and low-education groups separately. The DECO and the MMSE tended to perform better as screening tests for the higheducation subjects, but the differences were not statistically significant. In a later study, using a general population sample, Ritchie and Fuhrer (in press) found an area under the ROC of .88 for detecting dementia and no evidence that screening performance was affected by education. Gmm.t@y Scmen& Z&r&w jbr Demen& (CSI’D’). The CSI’D’ was designed as a dementia screening interview for use in cross-cultural studies (Hall et al., 1993). Specifically, it was designed for a study comparing Cree-speaking natives and Englishspeaking Canadians. The CSI’D’ consists of two components, a cognitive test of the subject and an interview with an informant, each translated into the appropriate language. The informant interview consists of 30 items covering memory and cognition, activities of daily living, miscellaneous problems, personality and depression. Only the ll-item Memory and Cognition scale is relevant here. Items on this scale are rated as No, Sometimes,or Yes. The mean scores on the scale were found to clearly differentiate demented and nondemented subjects in both the Cree- and English-speaking communities. Furthermore, the Cree- and Englishspeaking subjects had similar means within the demented and nondemented groups. These findings support the validity and crosscultural portability of the scale. The authors commented that the informant interview was more readily applicable to the two cultural groups than was the cognitive test. In more recent work, Hall et al. (1994) have used the CSI’D’ in a cross-cultural study of dementia in African Americans and Nigerians. The CSI’D’ appears to work satisfactorily as a screening test for dementia in both these groups, despite the high rate of illiteracy in the Nigerian elderly. However, separate data on the informant interview have not yet been reported. -Memcny &&iun~& (ShortMQJ. Koss, Patterson, Ownby, Stuckey, and Whitehouse (1993) developed the Short MQ from an analysis of data on a longer 32-item ques tionnaire which had previously been used to research self-reported memory problems. They had the questionnaire completed on 83 Alzheimer’s dementia patients and 39 controls who were spouses of these patients. Items were rated on a four-point scale from Almost never to Almost always. Informants completed the questionnaire for the patients, but the controls reported on themselves. It is a major methodological weakness of their study that the controls were not also reported on by informants. Discriminant analysis was used to select out 14 items which best discriminated the patients from the controls. These 14 items became the Short MQ. A factor analysis of the items suggested the existence of a general memory impairment factor. Validity was tested by correlating the Short MQ with a variety of other tests given to the patient group. Correlations were .50 with the Short Blessed Scale (a brief dementia screening test), .1’7 to .35 with memory tests, .41 with constructional praxis, .40 with expressive language, and .63 with activities of daily living. The Short MQ had small correlations with measures of psychiatric symptoms (r = .29 and .15) and virtually no correlation

62

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with education (r = .02). As a screening test for dementia, the Short MQ had a sensitivity of 94% and a specificity of lOO%, but these figures are probably inflated because the 14 items were chosen to maximally discriminate the two groups. Furthermore, the different methods used to gather data on the cases and controls may have distorted the results. Psylzho~Scales (PM). The PAS is designed to provide a multidimensional assessment of psychogeriatric disorders. It consists of two parts: an interview with a subject and an interview with an informant (Jorm & Mackinnon, 1994). The informant interview yields three scales: Cognitive Decline, Behaviour Change, and Stroke. Only the lo-item Cognitive Decline Scale is relevant here. This scale, like the IQCODE, MOQ2-RB and the DECO, asks the informant about changes in cognitive functioning. However, it does not specify an exact period over which change is rated, simply asking for comparison with “earlier in life.” The items for the scale were derived from a psychometric analysis of a larger pool of items administered to informants as part of an epidemiological survey of elderly people. A two-parameter latent trait analysis was used to select items having steep slopes (i.e., they were highly dis criminating items) and covering a range of thresholds (i.e., they covered a range of severity) (Jorm, Mackinnon et al., 1995). Validity was assessed by correlation with other tests in the epidemiological survey and by agreement with clinical diagnosis of dementia in two clinic samples. The Cognitive Decline scale correlated .48 with the MMSE and .78 with the IQCODE, but had low correlations with years of education (T = .Ol) and with the NART (r = .19), both of which are indicators of premorbid ability. Correlations were also low with scales measuring symptoms of anxiety ( r = .09) and depression (r = .12) in the subjects, showing evidence of divergent validity. Agreement with diagnosis of dementia was assessed with ROC curves, with the area under the ROC averaging .84 over the three samples. Population norms are available for the PAS derived from the epidemiological sample. These give percentile ranks using an Australian sample aged 70+ as the reference population.

Diagnostic Measures Clinical diagnosis of dementia usually requires both an examination of the subject and a history from an informant (Copeland et al., 1988; Roth et al., 1986, Social Psychiatry Research Unit, 1992; Zaudig et al., 1991). Although the informant history may be a very important component, particularly for mild dementia (Morris et al., 1991), it generally is not the sole basis for a diagnosis. However, in some research studies an examination of the subject is impossible, so that diagnosis must rest entirely on the data provided by an informant. This is particularly the case in studies of the family history of dementia. Because dementing diseases occur late in life, relatives of cases will often have died. Although medical records are an alternative source of information on deceased relatives, these are often hard to access and may not be informative about dementing diseases. Researchers have therefore devised standardized questionnaires and interviews to allow a diagnosis of dementia based solely on informant data.

(D@. The DQ is a 50-item questionnaire covering memory, language, difficulties in daily functioning, possible causes of dementia other than Alzheimer’s disease, contacts with medical professionals, and recognition of the problem in the family (Silverman, Breitner, Mohs, & Davis, 1986; Silverman, Eeefe, Mohs, & Davis, 1989). Diagnosis of dementia is made by a clinician using the informant data Dementia Qtu&nn&re

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63

(Silverman et al., 1989), but may also be made by a computer algorithm applied to the data (Kawas et al., 1994). Validity of the DQ has been assessed by Kawas et al. (1994). They used the DQwith informants of living subjects who had undergone a clinical diagnosis. The informants were interviewed by telephone and their data were used for making a diagnosis either by a clinician or by a computer algorithm. When a clinician made the diagnosis of dementia from the DQ the sensitivity was 100% and the specificity was 91%. Validity was almost as high for an algorithmic diagnosis, with a sensitivity of 95% and a specificity of 92%. Although the DQ performed very well at the diagnosis of dementia, the number of non-Alzheimer dementia cases was too small to evaluate its performance at differential diagnosis. K&&Lunum Ques&ma& Kukull and Larson (1989) did not set out to create a new assessment method, but rather to translate existing procedures for use by informants. They developed a questionnaire to implement the DSM-III criteria for dementia and primary degenerative dementia (American Psychiatric Association, 1980) and the Hachinski Ischemic Score (Hachinski et al., 19’75). The questionnaire includes examples or explanations to make the items understandable for laypersons. The aim is to distinguish Alzheimer’s disease from other dementias. To validate the questionnaire, Kukull and Larson (1989) mailed it out to informants of 36 autopsy confirmed cases of dementia. They found that the DSM-III criteria had a sensitivity of 93% and a specificity of 43% for the diagnosis of primary degenerative (Alzheimer’s) dementia. There were too few cases to allow an evaluation of the DSM-III diagnosis of multiinfarct dementia. The informant-based Hachinski score classified 40% of Alzheimer’s disease cases as multiinfarct dementia. On the basis of these findings, Kukull and Larson concluded that other information besides informant data was required for the differential diagnosis of dementing diseases. Kukull and Larson (1989) may have been overly pessimistic about the performance of informant-based diagnosis because all their cases were demented and the issue was one of differential diagnosis. Even standard diagnostic procedures can have substantial error rates for differential diagnosis when judged against pathological criteria (Brayne, Day, & Gill, 1992). It is not known how the questionnaire would perform at diagnosing dementia at the syndrome level, which is an easier task. No subsequent studies appear to have used the Kukull-Larson questionnaire. v Cou4teral Dementia Interuieu (RCDZ). The RCDI is a structured interview covering sociodemographic information, family history, physical health status, medications, hearing and vision, memory and orientation, behavior changes, and activities of daily living (Robins, Fischbach, & Davis, 1988). The interview can be administered by phone and takes approximately 40 minutes. A diagnosis is made using standard diagnostic criteria by the clinician who administers the RCDI. However, computer algorithms for diagnosis are reported to be under development (Davis et al., 1991). To validate the RCDI, Davis et al. (1991) compared retrospective diagnoses with lie diagnoses, medical records and pathologic diagnoses. Agreement with all of these standards was excellent. For example, taking pathological diagnosis as the validity standard, the RCDI had a sensitivity and specificity of 100% for diagnosis of dementia, and a sensitivity of 88% and a specificity of 80% for diagnosis of Alzheimer’s disease. Although these findings are impressive, the subjects used in the study were chosen to be clearly demented or normal and there were very few non-Alzheimer dementias. Performance of the RCDI is unlikely to be as good with more diagnostically challenging samples of subjects.

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Qudimmuk. The Informant-Based Questionnaire is a standard&d interview for the retrospective differentiation of hontotempotal dementia horn Alzheimer’s disease (Barber, Snowden, & Craufurd, 1995). The interview consists of screening questions for the presence of dementia and then a series of questions for differential diagnosis, covering memory/orientation, language, spatial skills, personality and behavioral changes, abnormal beliefs and perceptions, mood, and physical changes. On average, it takes 100 minutes to complete. The interview was validated with 18 confirmed cases of frontotemporal dementia and 20 of early-onset Alzheimer’s disease. Using the data collected, a scoring system was devised which perfectly separated the two groups. Although these initial findings are very promising, the Informant-Based Questionnaire needs cross-validation in other samples. ZrrfbnnwtBased

GENERAL ISSUES AND SUMMARY The informant measures reviewed above are quite diverse. They vary in terms of content domain (memory, a range of cognitive functions), period of functioning assessed (current functioning, change in functioning, retrospective assessment), method of gathering data (interview, selfcompleted questionnaire), and aim of assessment (measurement of a continuum, screening, diagnosis). This diversity makes it difficult to make generaliitions about informant-based assessment. Another diiculty is the lack of data on the intercorrelations among the informant-based measures. If these were known to be highly intercorrelated, it would be possible to generalize findings from one instrument to another. However, these instruments have been developed largely in isolation from one another and there is little information on their interrelationships. Despite these problems, there are some findings that emerge consistently across a variety of instruments and form the basis for some general conclusions about informant-based assessment of cognitive deficits. Factor Structure Some sort of factor analytic method has been used with items from four different instruments (Fuh et al., 1995; Jorm et al., 1989; Jorm & Jacomb, 1989; Jot-m, Mackinnon et al., 1994; Koss et al., 1993; Morales et al., 1995; Sunderland et al., 1984). In every case the authors found a large general factor. (Morales et al., 1995, rotated two factors, but these were correlated .52). This general factor has emerged even though some of the instruments were designed to assess a range of cognitive functions and not just memory. The conclusion that there is a general factor is supported by other studies reporting intercorrelations among subscales of informant instruments (Crockett et al., 1989; Schwartz, 1983). These correlations have been consistently high, despite fairly diverse item content. Reliability

Across all instruments, reliability has been found to be high, as summarized in Table 1. The high internal consistency coefficients confirm the homogeneity of the items revealed in factor analyses. Test-retest reliability is high for all scales except the Relatives’ Questionnaire, even over periods as long as a year or more. Inter-informant agreement has been less researched, but also appears to be high. Relationship

to Cognitive

Tests

Several informant scales have been correlated with cognitive screening tests for dementia. These cognitive screening tests often involve a heterogeneous set of items

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and aim to assess global cognitive impairment. As shown in Table 2, the correlations have been quite high, particularly considering the very different methods of assessment involved. In addition, informant scales have been correlated with a variety of more specialized cognitive tests. Consistently positive correlations have been reported with tests of episodic memory functioning, although the magnitudes vary considerably (Jorm, 1992; Jorm, Broe et al., in press; Koss et al., 1993; Lincoln & Tinson, 1989; McGlone, 1994; Sunderland et al., 1983, 1986). Other cognitive tests have not been used consistently enough to allow general conclusions. Relafionship to Diagnosis Most of the informant measures have been validated against diagnosis of dementia and performance has been good. However, other diagnoses have seldom been evaluated. Exceptions are work with head injured patients (Sunderland et al., 1983,1984) and with temporal lobectomy patients (McGlone, 1994; McGlone & Wands, 1991). With these other patient groups, discrimination has not been as great, which is not surprising given their generally milder deficits. The most interesting studies are those that compare an informant scale with a cognitive test as screening instruments for dementia. Several studies have compared informant scales with the MMSE, which is arguably the most commonly used cognitive screening test. Five studies have compared the IQCODE to the MMSE (Fuh et al., 1995; Jorm, 1994; Jorm et al., 1991; Jorm, Broe et al., in press; Morales et al., 1995) and one has compared the DECO with the MMSE (Kitchie & Fuhrer, 1992). In each of these comparisons, the informant scale performed as well, and sometimes it did better. SOME UNRESOLVED

Beyond these few broad generalizations, these are discussed below.

ISSUES

there are many unresolved issues. Several of

TABLE 2. Correlations Between Informant Scales and Cognitive Screening Tests

Informant Scale

Cognitive Screening Test

GERRI IQCODE IQCODE Short MQ PAS

MMSE MMSE Information/orientation Short Blessed Scale MMSE

Correlation .59** .37*, .41**, .54**, .61**, .69**, .75**, .78** .78** .50** .48**

Note. Abbreviations and references for data are: GERRI = Geriatric Evaluation by Relatives on Rating Instrument (Rozenbilds et al., 1986); IQCODE = Informant Questionnaire Cognitive Decline in the Elderly (Bowers et al., 1990; Christensen & Jorm, 1992; Fuh et al., 1995; Jorm, 1994; Jorm, Broe et al., in press; Jorm et al., 1989, 1991; ); Short MQ = ShortMemory Questionnaire (Koss et al., 1993); PAS = Psychogeriatric Assessment Scales (Jorm, Mackinnon et al., 1995); MMSE = Mini-Mental State Examination. *p < .05. **p < .OOl.

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Relationship to Education and Premorbid Ability Some informant measures (&&ODE, MOQ2, DECO, PAS) are intended to measure cognitive change and should therefore be independent of education and premorbid ability. Where the issue has been evaluated, independence has been found (Christensen 8cJorm, 1992; Fuh et al., 1995; Jorm, 1994, Jorm et al., 1989,199l; Jorm, Broe et al., in press; Jorm & Jacomb, 1989; Jorm, Mackinnon et al., 1995; Morales et al., 1995; Ritchie & Fuhrer, 1992). However, it is not known whether this is a general property of informant instruments or only applies to those assessing cognitive change. The only current functioning instruments to be studied in this regard are the PFQ, the CSI’D,’ and the Short MQ. The subscales of the PFQ had small correlations with education (Crockett et al., 1989), but the CSI’D’ and the Short MQdid not (Koss et al., 1993). Influence of Subject Depression Informant-based measures may reflect noncognitive as well as cognitive aspects of the subject’s behaviour. An important noncognitive influence could be depression. Most studies do not report data on depression, but where it has been reported there is generally a low correlation (Jorm, 1994; J orm, Mackinnon et al., 1995; Koss et al., 1993; McGlone et al., 1990), although one study did find a high relationship (Jorm, Broe et al., in press), probably because of the high prevalence of depressive symptoms in the sample. The available data are summarized in Table 3. It is possible that higher correlations are found in samples where the prevalence of depressive symptoms is greater. Although depression can have some effect on cognitive test performance, it seems to have a greater effect on cognitive complaints (Bolla et al., 1991; Jorm et al., 1994; Kahn et al., 19’75; M&lone et al., 1990; O’Connor et al., 1990; O’Hara et al., 1986). Any influence of depression on informant-based measures could therefore be partly mediated by the subject’s cognitive complaints.

TABLE 3. Correlations Between Informant Measures and Depressive Symptoms in the Subject

Informant Measure IQCODE MOQ2 Short MQ PAS Brief measures

Correlation .14***, .45*** non-significantr .15 .12** .09*, .09*, .10*, .13**

Note. Abbreviationsand references for data are: B&ODE = Informant Questionnaire on Cognitive Decline in the Elderly (Jorm, 1994; Jorm, Broe et al., in press); Short MQ = Short-Memory Questionnaire (Koss et al., 1993); PAS = Psychogeriatric Assessment Scales (Jorm, Mackinnon et al., 1995); Brief measures (Jorm et al., 1994). *p < .05. **p < .Ol. ***p < .OOl.

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Influence of Cognitive Complaints Although self-reported cognitive functioning is only weakly related to cognitive test performance, it could have a stronger relationship with informant-based measures. It is plausible that informants will be influenced by any cognitive complaints they hear from the subject. Studies have reported variable, sometimes sizeable, correlations between self-reported and informant-reported cognitive functioning (Grut et al., 1993; Jorm et al. 1994; Jorm, Broe et al., in press; Lincoln 8c Tinson, 1989; McGlone et al., 1990; McGlone & Wands, 1991; Sunderland et al., 1983,1986; Taylor, 1990). These correlations are summarized in Table 4. A related issue is whether the discrep ancy between self reports and informant reports provides useful information in itself. Judging from the varying correlations in Table 4, lack of awareness of cognitive deficits might vary greatly among diagnostic groups. Influence of informant Characteristics A major issue for informant-based methods is whether some informants will provide less valid information than others. If so, some prescreening of informants would be necessary. Researchers have often ignored the issue, but there has been work done on certain informant characteristics: the age of the informant, the degree of contact between the informant and the subject, the affective state of the informant, and the quality of the informant-subject relationship. The potential influence of age was first raised by Sunderland et al. (1986). In a study of elderly subjects, they found poor correlations between informant assessments and cognitive tests. They explained their poor results in terms of the age of the informants, most of whom were also elderly. Elderly informants are as likely as elderly sub jects to have memory problems and may therefore not provide valid assessments. Subsequently, two studies have examined whether there is a correlation between the informant’s age and the degree of cognitive impairment they rate in the subject

TABLE 4. Correlations Between Self- and Informant-Report Measures of CognitiveFunctioning Informant Measure Relatives’ Questionnaire IQCODE MOQ2 Brief measuresa

Correlation .09, .35**, .45**, .58**, .72***, .72*** .45*** non-significant r, .23*, .63*** .10-i-, .17***, .18***, .21***, .24***

Note. Abbreviations and references for data are: Relatives’ Questionnaire (Lincoln & Tinson, 1989; Sunderland et al., 1983; Taylor, 1990); IQCODE = Informant Questionnaire on Cognitive Decline in the Elderly (Jorm, Broe et al., in press); MOQ2 = Memory Observation Questionnaire 2 (McGlone et al., 1990; McGlone & Wands, 1991); Brief measures (Grut et al., 1993; Jorm et al., 1994). %appa coefficients. *p < .05. **p < .Ol.

***p < .OOl. -jSignificance not stated.

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A.B Jinm

(Jorm, Broe et al., in press; Jorrn & Jacomb, 1989). Neither study found any relationship. However, correlations with informant’s age do not address the issue of whether there is differential validity of the ratings provided by young and older informants. The only study on this issue looked at the correlation between the IQCODE and MMSE separately for younger and older informants and found no difference (Jonn et al., 1991), but differential validity needs to be examined in much larger samples using ROC analysis as well as correlations with cognitive tests. Perhaps the real issue is not the age of the informant, but the level of cognitive functioning required for an informant to provide valid ratings. Another variable which could affect the validity of an informant’s assessment is the amount of contact they have with the subject, particularly whether or not they live with the subject. It has been reported that informant ratings do not differ for spouses, children, and others (Fuh et al., 1995; O’Connor et al., 1989), nor by the length of time since the informant lived with the subject (Fuh et al., 1995; Jorm & Jacomb, 1989). However, the issue of differential validity as a function of amount of contact has not been addressed. Another possible influence is the informant’s affective state. It is well known that depression can be associated with cognitive distortions (e.g., Seligman, 1990). Depression might therefore affect the informant’s perception of the subject’s behaviour. Several studies have found small but statistically significant correlations between anxiety and depression scores in the informant and their ratings of the subject’s cognitive functioning (Jorm, Broe et al., in press; Jorm, Christensen et al., 1994; Jorm, Mackinnon et al., 1995), although another study found near zero correlations (Jorm, 1994). These correlations are summarized in Table 5. It can be seen that correlations with anxiety are of similar magnitude to those with depression, perhaps reflecting the high correlations between anxiety and depression scales. Where associations have been found, the relationship could be one of either cause or effect, with cognitive impairment causing stress to the informant or the informant’s affective state influencing their perception of the subject. However, there is evidence to support the perception hypothesis. Jorm, Broe et al. (1995) also used the MMSE and found that it was uncorrelated with the informant’s affective state, in contrast to the informantbased cognitive assessment. Similarly, Jorm, Christensen et al. (1994) found that the informant’s depression score was correlated with their cognitive rat-

TABLE 5. Correlations Between Informant Measures and Depressive and Anxiety Symptoms in the Informant

Informant Measure

Correlation With Depression

Correlation With Anxiety

IQCODE PAS

.06, .22** .17***

.08*, .23** .16***

Brief measures

.07*, .09*, .09*, .11**

.lO**, .ll**,

.14***, .16***

Note. Abbreviations and references for data are: IQCODE = Informant Questionnaire on Cognitive Decline in the Elderly (J orm, 1994; Jorm, Broe et al., in press); PAS = Psychogeriatric Assessment Scales (Jorm, Mackinnon et al., 1995); Brief measures (Jorm et al., 1994). *p < .05. **p< .Ol. ***p < .OOl.

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ings even after the influence of MMSE score was partialled out. Further research is needed to establish the generality of these findings. The quality of the relationship between the informant and the subject could influence the informant’s perception of the subject’s cognitive functioning. The only research on the issue used the Interpersonal Bonding Measure (Wilhelm & Parker, 1988) to assess this association. This measure gives separate scales for degree of care and control received from the spouse. In a study with wives as informants, Jorm, Broe et al. (1995) found that both low care and high control were correlated with informant-based assessment of cognitive decline (r of .24 and .34, respectively). Again, a correlational study cannot establish whether the quality of the relationship affects ratings of cognitive decline or cognitive decline affects perception of the relationship. However, the same study also used the MMSE and it had near zero correlations with care and control. It is therefore likely that the quality of the relationship affects the informant’s cognitive ratings, rather than vice versa. However, more research is needed before any firm conclusion can be drawn. Taken together, the evidence suggests that the affective state of the informant and the quality of the informant-subject relationship can bias the information provided. However, there is as yet little evidence on whether some informants provide less valid data than others. Further work on the issue would be valuable because it would pro vide users of informant-based methods with a basis for screening out informants who are likely to be less valid. What is the General Factor Measuring? Although there is a consistent finding of a general factor, we do not know what this is measuring. The global effects of dementia could produce the general factor, but not all studies finding it have involved dementing subjects. One suggestion is that this factor reflects the subject’s episodic memory functioning (Jorm, 1992), but it is clear that other influences are involved, including other cognitive functions (e.g., reaction time), depressive symptoms in the subject, and characteristics of the informants (Jorm, Broe et al., in press). As mentioned earlier, a possible reason for the emergence of the general factor is that everyday cognitive tasks covered by informant instruments are by their nature complex and involve many specific abilities. It is also possible that ‘the general factor lies in the perception of the informant rather than in the subject’s behavior. Factor analysis of cognitive tests also produces a general factor, but there are important subfactors as well (Carroll, 1993) and these have not emerged in informant assessments. However, further work is needed in this area before the possibility of more specific informant instruments is dismissed. Carroll’s (1993) work with cognitive tests suggests a number of specific domains which could be investigated. Assessing Higher Levels of Cognitive Functioning Informant measures have aimed to assess cognitive impairment and it is clear that they discriminate well within the lower range of cognitive functioning. By contrast, cognitive tests have been developed to cover the whole range of cognitive functioning, including higher functioning. It is not known whether informant-based measures can also be developed to assess higher levels of functioning. Although considerable attention has been given to establishing item validity, the issue of item difficulty has been neglected.

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CONCLUSION Although clinicians commonly use information provided by informants, standardized informant instruments are comparatively new and not well known. However, the existing evidence strongly supports the reliability and validity for these instruments for assessing cognitive impairment and decline. They provide data on cognitive functioning in everyday life which can complement the findings from cognitive tests, and they can be used as a substitute in situations where cognitive testing is not possible (e.g., with deceased subjects). These methods are probably of most use in screening for dementia, where they have been found to perform as well as brief cognitive screening tests like the MMSE. However, informant-based methods are limited to pro viding global infomation about cognitive functioning, in contrast to the assessment of specific functions which can be provided by cognitive tests.

- The following individuals provided suggestions for improving thii paper: Mike Bird, Helen Christensen, and Scott Henderson.

Acknowledgements

REFERENCES American Psychiatric Association. (1980). LXugnastic and statistical manual of mental disom& (3rd ed.). Washington, DC: Author. Barber. R., Snowden, J. S., & Craufurd, D. (1995). Frontotemporal dementia and Alzheimer’s disease: Retrospective differentiation using information from informants. Jmcmal of Ncumle~, Neunxurgcrl and Psych&y, 59,61-70. Blessed, G., Tomlinson, B. E., & Roth, M. (1968). The association between quantitative measures of dementia and of senile change in the cerebral grey matter of elderly subjects. British Journal of Pychiahy, 114, 797-811. Bolla, K. I., Lindgren, K N., Bonaccorsy, C., & Bleecker, M. L. (1991). Memory complaints in older adults. Archives ofNeurology, 48,61-64. Bowers, J., Jorm, A. F., Henderson, S., 8c Harris, P. (1990). General practitioners’ detection of depression and dementia in elderly patients. Medical Journal ofAustralia, 153.192-196. Brayne, C., Day, N., & Gill, C. (1992). Methodological issues in screening for dementia. Nnrrogidmriology, 1I(Suppl. l), 88-93. Carroll, J. B. (1993). Human cognitive abilities: A suruq of facfor_aMlytic studies. Cambridge: Cambridge University Press. Christensen, H., & Jorm, A. F. (1992). The effect of premorbid intelligence on the Mini-Mental State and R&ODE. Int&ruttial Journal of Geriatric Psychiatry, 7, 159-160. Copeland, J. R. M., Dewey, M. E., Henderson, A. S., Kay, D. W. R, Neal, C. D., Harrison, M. A. M., McWilliam, C., Forshaw, D., & Shiwach, R. (1988). The Geriatric Mental State (GMS) used in the community: replication studies of the computerized diagnosis AGECAT. Psychological Medicine, 18,219-223. Crockett, D., Tuokko, H., Koch, W., & Parks, R. (1989). The assessment of everyday functioning using the Present Functioning Questionnaire and the Functional Rating Scale in elderly samples. clinical Gmmtdogist, 24, 3-25. Davis, P. B., White, H., Price, J. L., McKee], D., & Robins, L. N. (1991). Retrospective postmortem dementia assessment. Archives of Neurology, 48,613-617. Erkinjuntti, T., Hokkanen, L., Sulkava, R., & Palo, J. (1988). The Blessed dementia scale as a screening test for dementia. Intematixmal Journal of Geriatric Psychiaty, 146,267-273. Folstein, M. F., Folstein, S. E., & McHugh, P. R. (1975). ‘Mini-Mental State’: A practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research, 12, 189-198. Fuh, J. L., Teng, E. L., Lin, K N., Larson, E. B., Wang, S. J., Liu, C. Y., Chou, P., Kuo, B., I. T., & Liu, H. C. (1995). The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) as a screening tool for dementia for a predominantly illiterate Chinese population. Nemology, 45, 92-96. Gnu, M., Jorm, A. F., Fratiglioni, L., Forsell, Y., Viitanen, M., & Wtnblad, B. (1993). Memory complaints of elderly people in population survey: Variation according to dementia stage and depression. Journal of tke American Geriatrics Society, 41, 1295-1300.

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