CAN AN INFORMANT QUESTIONNAIRE BEUSED TO PREDICT THE DEVELOPMENT OF

DEMENTIA IN MEDICAL INPATIENTS?BEVERLEY LOUIS1, DANIEL HARWOOD2, TONY HOPE3 AND ROBIN JACOBY4*

1Senior Registrar, University of Oxford Department of Psychiatry, Warneford Hospital, Oxford, UK2MRC Research Fellow, University of Oxford Department of Psychiatry, Warneford Hospital, Oxford, UK

3University Lecturer in Practice Skills and Honorary Consultant Psychiatrist, University of Oxford,Department of Psychiatry, Warneford Hospital, Oxford, UK

4Professor of Old Age Psychiatry, University of Oxford Department of Psychiatry, Warneford Hospital, Oxford, UK

SUMMARY

Objective. To determine whether elderly medical inpatients without dementia who score43.31 on the short form ofthe Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) are at an increased risk of developingdementia.

Design/participants. Twenty-nine patients with an IQCODE score of43.31 without dementia and 29 age- and sex-matched controls, from an original sample of 201 medical inpatients over 65, were examined 17±24 months afterinitial assessment.

Setting. Interviews took place in patients' homes, but all subjects had been recruited while medical inpatients in ageneral hospital 17±24 months previously.

Measures. The IQCODE and clinical interview to make DSM-III-R diagnosis of dementia.Results. Ten of the study group and one control had developed dementia since the original assessment.Conclusions. Non-demented elderly medical inpatients with an admission IQCODE score of43.31 are more likely

to develop dementia than those with an IQCODE score of53.31. The IQCODE is a sensitive tool for detecting earlydementia. Copyright # 1999 John Wiley & Sons, Ltd.

KEY WORDSÐIQCODE; dementia; cognitive disorders; inpatients

The identi®cation of dementia in medical inpati-ents is important for discharge planning, and withthe development of more e�ective anti-dementiadrugs may acquire even greater importance. Whilemedical sta� probably detect most patients withclinically signi®cant dementia, milder cognitiveimpairment may be overlooked (Harwood et al.,1997a).

A standardized history of cognitive decline takenfrom an informant, using an instrument such as theInformant Questionnaire on Cognitive Decline inthe Elderly (IQCODE), is an accurate method ofdetecting dementia in inpatient and communitysettings (Jorm, 1996). Harwood et al. (1997b)evaluated the short form of the IQCODE (Jorm,

1994) as a screening tool for dementia in 201 elderlymedical inpatients and found it to have a higherspeci®city and sensitivity for detecting dementiathan the commonly used Abbreviated Mental TestScore (AMT) (Hodkinson, 1972). In addition,many of the `false positive' cases identi®ed by theIQCODE had clear histories of cognitive declinealthough they did not ful®l DSM-III-R diagnosticcriteria for dementia. In view of the evidence thatpeople with mild cognitive impairment have anincreased risk of developing dementia (Petersenet al., 1995), it was possible that this group of`IQCODE false positives' shared a similar risk. Ifso, a positive IQCODE score in the absence ofdementia might predict those at risk of developingdementia.

We sought to examine this issue by reassessingtwo groups of patients from our original study:®rst, the group with an IQCODE score in the`dementia' range who did not ful®l DSM-III-R

CCC 0885±6230/99/110941±05$17.50 Received 9 November 1998Copyright # 1999 John Wiley & Sons, Ltd. Accepted 27 April 1999

INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY

Int. J. Geriat. Psychiatry 14, 941±945 (1999)

*Correspondence to: Professor R. Jacoby, Section of Old AgePsychiatry, University of Oxford Department of Psychiatry,Warneford Hospital, Oxford OX3 7JX, UK. Tel.: (01865) 223639. Fax: (01865) 249 253.

criteria for dementia and second, a control groupwho had IQCODE scores in the normal range. Ourhypothesis was that those with a positive IQCODEscore would have a higher prevalence of dementiaat follow-up than the control group.

METHOD

This study involved the further assessment of twosubgroups of subjects from a larger study on thedetection of cognitive impairment in medicalinpatients which has been described in detail else-where (Harwood et al., 1997a, b). The originalstudy investigated a random sample of 201 medicalinpatients over 65 admitted to a large teachinghospital over a 4-month period. Subjects under-went a brief clinical interview which incorporatedthe Abbreviated Mental Test (Hodkinson, 1972)and the Mini-Mental State Examination (MMSE)(Folstein et al., 1975) within 48 hours of admission.Medical notes were examined and the IQCODEwas administered to a relative. Using this informa-tion, DSM-III-R psychiatric diagnoses were made.

The 30 subjects whose original IQCODE scorewas greater than 3.31 but who did not ful®l DSM-III-R criteria for dementia were followed up;3.31 was the cuto� point found in previous studiesto be most discriminating between those patientswith and without dementia (Jorm, 1994).

The control group consisted of 30 subjects fromthe original study whose IQCODE score was lessthan or equal to 3.31, ie in the normal range, andwho did not ful®l DSM-III-R criteria for dementia.Each control was identi®ed by matching for sex,and as near as possible for age, with a subject in thestudy group.

With the consent of their general practitioner(GP), a letter was sent to each subject invitingparticipation in the study. For subjects who haddied since the original study, a letter was sent to therelative who had taken part in the IQCODEinterview in the original study.

Interviews took place in the subject's home andwere held as close as possible to 18 months after theoriginal assessment. All interviews were conductedby the same investigator (BL), who was blinded asto whether a participant was a subject or control.

For living subjects, two interviews were carriedout: one with the subject and one with the relative.The interview with the subject consisted of astructured checklist of DSM-III-R symptoms ofdementia, delirium and depression followed by

administration of the MMSE and GeriatricDepression Scale (GDS) (Yesavage et al., 1983).The interview with the relative included a furtheradministration of the IQCODE as well as theDSM-III-R checklist of symptoms.

For subjects who had died since the originalassessment, the informant interview was of asimilar format, obtaining information on thesubject's mental state before death and includinga retrospective IQCODE interview.

GP and hospital medical notes were scrutinizedfor all subjects. The GPs of patients who did notconsent to an interview were contacted by letterand asked to indicate the cognitive status of thesubject according to one of the following threecategories: de®nite dementia, probable dementia,or no evidence of dementia.

A DSM-III-R diagnosis of cognitive impair-ment, based on the best available information, wasestablished for all study subjects and controls at thetime of the follow-up interview or, in the case ofthose subjects who had died since the originalstudy, before death.

Data analysis compared the proportion of thosewith a DSM-III-R diagnosis of dementia in thestudy and control groups using the chi-squared orFisher's Exact Test as appropriate. Mortality ratesin the two groups since follow-up were alsocompared. The statistical package used was SPSSfor Windows (version 6.1.1).

RESULTS

Thirty study subjects were identi®ed but one couldnot be traced. Twenty-nine subjects were thereforeavailable for the study, with an age- and sex-matched control group. The average age of bothgroups was 80 years (range 66±98) and 57% ofeach group was male.

In the study group, 13 out of 29 subjects had diedsince the original study. Of the 16 still alive,10 participated in an interview and six did notconsent. However, limited information from theGP was available for four of the non-consenters.Of the 13 deceased subjects, information was avail-able from an informant in six cases and from theGP in only one case.

In the control group, seven out of 29 had diedsince the original study. Of the 22 living, 12 part-icipated in the interview and 10 did not consent.GP information was available for eight of the non-consenters. Of the seven who had died, information

Copyright # 1999 John Wiley & Sons, Ltd. Int. J. Geriat. Psychiatry 14, 941±945 (1999)

942 B. LOUIS, D. HARWOOD, T. HOPE AND R. JACOBY

was available from an informant in four cases andfrom the GP in a further three. Interviews tookplaced at an average of 20 months after the originalassessment (range � 17±24 months).

Mortality rate

Table 1 shows the mortality since the originalstudy in the two groups.

Prevalence of dementia

Table 2 shows the prevalence at follow-up ofDSM-III-R dementia, which was the main out-come measure, in the two groups. Table 3compares the prevalence of di�erent DSM-III-Rdiagnoses of cognitive impairment in the originalstudy and at follow-up.

The follow-up diagnosis column also includesestimated diagnoses at time of death for subjectswho died between the two studies.

The total number of original diagnoses in thesubject group is 31, not 29, because of comorbidity

in two subjects who had both delirium and mildcognitive impairment.

It was not possible to make a diagnosis for somepatients because of insu�cient information. Thisgroup included both those patients alive at thetime, but who did not consent to interview, whoseGPs felt unable to comment on their cognitivestatus (eg if seen infrequently) (N � 2 in bothgroups) and those who had died, but whosehospital and GP notes made no reference to theircognitive status (N � 6 in study group). In all casesdiagnosed as dementia at follow-up (except one),the diagnosis was made on the basis of clinicalinterview with patient or relative. For the oneexception, the diagnosis was made by the GP.

DISCUSSION

This study has shown that elderly medical inpati-ents with an IQCODE score of 43.31 on admis-sion but who do not ful®l DSM-III-R criteria fordementia are more likely to develop dementia inthe next 20 months than an age- and sex-matchedgroup with an initial IQCODE score of 53.31.This suggests that the IQCODE, being sensitive tomild degrees of cognitive decline, is capable ofdetecting patients in the early stages of a dementingillness before their cognitive impairment is detect-able on formal testing.

The di�erence in mortality between the twogroups just failed to reach statistical signi®cance.Other researchers have described an increasedmortality in patients with mild cognitive impair-ment (Gussekloo et al., 1997) and it is possible thatthe numbers in our study were too small to pickthis up.

Because this was a follow-up of a subgrouprecruited from a previous study, the number ofsubjects in each group was small and data are

Table 1. Comparison of mortality in subject and controlgroups

Alive Dead

Controls 22 (76%) 7 (24%)

Subjects 16 (55%) 13 (45%)

Note: Chi-squared � 2.75, df � 1, p � 0.097.

Table 2. Number of subjects with dementia at follow-upin two groups

Yes No Unknown

Controls 1 26 2

Subjects 10 11 8

Note: Fisher's Exact Test, p � 0.0004.

Table 3. Psychiatric diagnosis at follow-up

Diagnosis Controls Subjects

Original Follow-up Original Follow-up

No cognitive impairment 28 23 3 6

Dementia 0 1 0 10

Mild cognitive impairment 1 2 22 4

Delirium 0 1 4 0

Depression 0 0 2 1

Insu�cient information for diagnosis 0 2 0 8

Copyright # 1999 John Wiley & Sons, Ltd. Int. J. Geriat. Psychiatry 14, 941±945 (1999)

CAN THE IQCODE BE USED TO PREDICT DEMENTIA? 943

missing on some subjects who refused to partici-pate.

A potential criticism of the study would be thesigni®cant number of subjects whose diagnosis wasunknown at follow-up. However, even if bothpatients in the control group with an unknowndiagnosis in fact had dementia, and none of theeight subjects in the subject group had dementia atfollow-up, the proportions with dementia atfollow-up of the two groups would still be signi®-cantly di�erent (chi-squared � 4.86, p � 0.028,df � 1).

There are several potential sources of bias in thisstudy which will be discussed below.

First, di�erences in baseline rates of physicalillness between the two groups may partly explainthe ®ndings. Greater illness severity might explainan increased risk of dementia through disorderssuch as cerebrovascular disease which a�ect cogni-tive function. In the original study no data werecollected on physical illness, so it is not possible torule this out.

Second, the baseline rates of delirium anddepression were higher in the study group thanthe control group. The higher IQCODE scores inthe study group may have partly re¯ected cognitiveimpairment secondary to delirium and depressionas well as early dementia. However, althoughdepression carries an increased risk of developingdementia (Devanand et al., 1996), dementia alsopredisposes to depression (Ballard et al., 1996).Mild dementia is also a risk factor for delirium(Schor et al., 1992). So, if more of the subjects inthe study group had an early dementing illness thanthose in the control group, it may not be surprisingthat this group had higher baseline rates ofdelirium and depression.

Third, informants who scored their relatives asIQCODE `positive' at baseline may have been morelikely to be critical of their relatives' cognitivefunctioning at the follow-up assessment than thecontrol group informants. Given that endpointdiagnoses were made partly on the basis ofinformation from informants, this might have ledto a higher number of false positive dementia diag-noses in the study group than in the control group.

Fourth, in cases where informant or subjectinterviews were lacking, the GP's `best guess'diagnosis assumed importance in making a ®naldiagnosis of dementia or not dementia. GPs mayhave been biased towards making a diagnosis ofdementia for subjects in the study group who hadhigher levels of mild cognitive impairment of which

the GPs might have been aware. However, thisassumes that the GPs would have had fairlydetailed knowledge of the cognitive status of theirpatients, which is far from certain.

The IQCODE is essentially a quick method oftaking a structured history, and the high baselineIQCODE scores in the study group probablysimply indicate that informants were aware of anearly dementing process a�ecting their relatives atthe ®rst interview. However, the IQCODE may bea particularly useful method for the screening forearly cognitive decline in a medically unwell groupof patients in whom the results of cognitive assess-ment might be di�cult to interpret, because ofphysical illness and delirium.

Ideally, the study should be replicated in a largersample with subject and control groups matchedfor presence of delirium and, as far as possible, forillness severity. However, it seems unlikely that thelimitations described above completely negate our®ndings.

CONCLUSIONS

We have already demonstrated the value ofIQCODE as a tool for detecting dementia inmedical inpatients (Harwood et al., 1997a, b). Wenoted that the IQCODE is a brief and simplescreening tool which has the potential to beincorporated into the admitting nurse's or houseo�cer's interview with relatives of older patients. Itwould seem reasonable that patients who scorewithin the dementia range on screening shouldundergo further cognitive testing and have a

. Elderly medical inpatients whose admissionscore is 43.31 on the Informant Question-naire on Cognitive Decline in the Elderly(IQCODE) (short form) had an increasedrisk of developing dementia in the next17±24 months

. The IQCODE (short form) has potential notonly as a screening tool for dementia but alsoas a means of detecting those at risk ofdeveloping dementia

. The study is small with sources of possiblebias, and requires replication in a largersample

Copyright # 1999 John Wiley & Sons, Ltd. Int. J. Geriat. Psychiatry 14, 941±945 (1999)

944 B. LOUIS, D. HARWOOD, T. HOPE AND R. JACOBY

further history obtained from the relatives to clarifywhether or not they have dementia. The ®ndingsfrom this study suggest that the group of patientswith an IQCODE score of greater than 3.31. whodo not have dementia are, however, at increasedrisk of developing dementia and should be followedup to see whether their apparent cognitive declinecontinues after their discharge from hospital.

ACKNOWLEDGEMENTS

We thank the patients' relatives and GPs whoparticipated in this study, and the sta� at the JohnRadcli�e Hospital, Oxford who enabled theoriginal study to be undertaken.

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