Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE)

Development of the IQCODE

The IQCODE was developed from a study of 39 interview questions assessing changes in memory and intelligence in older people. ¹ Informants were asked to rate older people for the degree of change over the previous 10 years in 39 aspects of everyday cognitive functioning. From this initial study, the number of questions was reduced to 26 which correlated well together and were feasible to rate for most informants. These questions were then formatted for self-completion by an informant. In its present form, the IQCODE requires each question to be rated on a 5-point scale from (1) “much improved” to (5), “much worse”. ²

Subsequently, based on data from a number of studies, a short version of the IQCODE was developed, involving only 16 questions. ³ This Short IQCODE was found to correlate very highly (0.98) with the full version and to have equal validity as an indicator of dementia. For this reason, the Short IQCODE is nowadays generally used in place of the original 26-item version.

The original IQCODE was in English. However, versions have been developed in many other languages, including Chinese, Danish, Dutch, Finnish, French, Canadian French, Finnish, German, Italian, Japanese, Korean, Lithuanian, Norwegian, Persian, Polish, Portuguese, Spanish, and Thai. Copies of the IQCODE in various languages are available for download at the end of this article or from http://cmhr.anu.edu.au/ageing/Iqcode/.

There is also a Retrospective IQCODE which is used to assess a person who is deceased. This questionnaire has found use in neuropathological studies where a brain has been donated post-mortem, but no cognitive assessment was carried out when the person was alive, or in studies of stroke patients where the person’s cognitive state before the stroke needs to be assessed retrospectively.

Administration and Scoring of the IQCODE

The IQCODE is generally used as a pen and paper test. It takes around 10-25 minutes to complete depending on the version chosen (26- or 16-items) and is generally found relatively easy to answer. It can be mailed to informants and or administered by telephone.

Most often, the IQCODE has been scored by summing the items and dividing by the number of items (either 26 or 16), thus producing a summary measure ranging from 1 to 5, with a score of 3 indicating no change and one of greater than 3 indicating that some decline has occurred. However, some users have preferred adding up all items to give a total score. Community norms for Australia have been developed  for age groups from 70+ years. ⁴ For dementia screening, a cutoff is used, with scores above the cutoff indicating probable dementia. The cutoff has ranged from 3.3-3.6 in community samples to 3.4-4.0 in patient samples. ⁵

Validity of the IQCODE

Numerous studies have found that the IQCODE can discriminate dementia patients from those without dementia.  The IQCODE performs as well as the Mini-Mental State Examination as a screening test for dementia. ⁶ The IQCODE has been shown predict new cases of dementia in stroke patients and in hospital in-patients over 2-3 years follow-up. ^{7 8}

Correlations between the IQCODE and the Mini-Mental State Examination range from -0.37 to -0.78 ⁹ with an average of -0.58, showing that they largely overlap in what they assess, but have some unique components as well. As a consequence, a number of studies have investigated whether the concurrent of both the IQCODE and the MMSE improves dementia detection. These studies generally reported somewhat increased sensitivity and/or specificity of the combined tests, but cost-benefits of this combination varied depending on the method used or the type of sample assessed. ¹⁰

Independence of education and culture

A major problem with cognitive screening tests is that are associated with level of education, socio-economic status and use of a non-dominant language in the person’s culture. For example, scores on the Mini-Mental State Examination have been shown to be affected by gender, age, education, cultural background, language spoken at home, socio-economic status, occupation and presence of a mood disorder. ¹¹  By contrast, the IQCODE has been shown to be little influenced by education and by proficiency in the language of the country of residence. ¹² However, small associations between the IQCODE and anxiety and depression have been reported. ¹³ They may be due mood disorders directly affecting cognitive function or to the fact that informant may have difficulty distinguishing between cognitive decline and depression and anxiety.

Downloads of IQCODE in various languages

References

1. ↑Jorm AF, Korten AE. Assessment of cognitive decline in the elderly by informant interview. Br J Psychiatry. 1988 Feb;152:209-13.

2. ↑Jorm AF. A short form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): Development and cross-validation. Psychological Medicine. 1994 Feb 1994;24(1):145-53.

3. ↑Jorm AF. A short form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): Development and cross-validation. Psychological Medicine. 1994 Feb 1994;24(1):145-53.

4. ↑Jorm AF, Jacomb PA. The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): socio-demographic correlates, reliability, validity and some norms. Psychol Med. 1989 Nov;19(4):1015-22.

5. ↑Jorm AF. The Informant Questionnaire on cognitive decline in the elderly (IQCODE): a review. Int Psychogeriatr. 2004 Sep;16(3):275-93.

7. ↑Henon H, Pasquier F, Durieu I, Godefroy O, Lucas C, Lebert F, et al. Preexisting dementia in stroke patients. Baseline frequency, associated factors, and outcome. Stroke. 1997 Dec;28(12):2429-36.

8. ↑Louis B, Harwood D, Hope T, Jacoby R. Can an informant questionnaire be used to predict the development of dementia in medical inpatients? Int J Geriatr Psychiatry. 1999 Nov;14(11):941-5.

9. ↑Jorm AF. The Informant Questionnaire on cognitive decline in the elderly (IQCODE): a review. Int Psychogeriatr. 2004 Sep;16(3):275-93.

10. ↑Jorm AF. The Informant Questionnaire on cognitive decline in the elderly (IQCODE): a review. Int Psychogeriatr. 2004 Sep;16(3):275-93.

11. ↑Tombaugh TN, McIntyre NJ. The mini-mental state examination: a comprehensive review. J Am Geriatr Soc. 1992 Sep;40(9):922-35.

12. ↑Jorm AF. The Informant Questionnaire on cognitive decline in the elderly (IQCODE): a review. Int Psychogeriatr. 2004 Sep;16(3):275-93.

13. ↑Jorm AF. The Informant Questionnaire on cognitive decline in the elderly (IQCODE): a review. Int Psychogeriatr. 2004 Sep;16(3):275-93.