Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE)

Abstract

The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) is an extensively validated psychometric tool designed to assess changes in an individual’s cognitive function over the preceding 10 years, based on the observations of a close informant (e.g., family member or caregiver). Developed by Jorm in 1989, the IQCODE serves primarily as a rapid and reliable screening instrument for dementia and significant cognitive decline in older populations. Its strength lies in utilizing real-world functional observations rather than direct testing, providing a measure of decline relative to the individual’s baseline ability.

Keywords

IQCODE, Informant Questionnaire, Cognitive Decline, Dementia Screening, Geriatric Assessment, Alzheimer’s Disease, Psychometrics, Elderly.

Authors

Anthony F. Jorm, P.A. Jacomb, R. Scott, J.S. Cullen.

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Purpose

The primary purpose of the IQCODE is to facilitate the early identification and screening of cognitive decline, particularly in settings where comprehensive neuropsychological testing may be impractical or resource-intensive. By utilizing the perspective of an informant who has known the subject well over a long period, the scale aims to quantify the rate and severity of decline in everyday functional and memory abilities.

It is widely used in clinical research, epidemiological studies, and primary care settings as a cost-effective and reliable method for identifying individuals who may require further diagnostic evaluation for conditions such as dementia. The scale compares the subject’s current functioning across various domains to their remembered functioning 10 years prior, providing a standardized measure of change.

Construct

The IQCODE measures the construct of change in cognitive ability as perceived by a reliable observer. This differs fundamentally from scales that measure current cognitive status directly. Specifically, it focuses on decline across multiple facets of daily life that are highly sensitive to the onset of dementia, including aspects of memory, orientation, executive function, and judgment.

The items are structured to capture subtle, real-world manifestations of cognitive impairment, such as difficulties with financial management, learning new tasks, or recalling recent events. The 10-year reference period is crucial, as it allows the assessment to isolate pathological decline from stable, lifelong variations in intelligence or education.

Validity

The IQCODE has demonstrated strong empirical validity across numerous international studies. Its primary strength lies in its ability to correlate highly with objective measures of cognitive function, such as the Mini-Mental State Examination (MMSE), and clinical diagnoses of dementia (e.g., Alzheimer’s disease). It shows high diagnostic accuracy when used as a screening tool.

Specific research has confirmed its concurrent and predictive validity. Studies by Jorm et al. (1991) established its effectiveness as a screening test for dementia, noting high sensitivity and specificity. Furthermore, the scale’s ability to predict the subsequent development of dementia in medically ill patients has been established, indicating strong predictive utility (Lewis et al., 1994). Validation against long-term change on cognitive tests over periods of seven to eight years also confirms its utility in longitudinal studies (Jorm et al., 2000).

Reliability

The reliability of the IQCODE is generally considered excellent, particularly its inter-rater and internal consistency reliability. Because the scale relies on the consistency of the informant’s observations regarding change over time, inter-rater reliability is crucial and has been consistently reported as high, especially among spouses or close family members who interact daily with the subject.

Internal consistency, measured typically using Cronbach’s alpha, is consistently high, often exceeding 0.90 for the full 26-item version, indicating that the items effectively measure a single underlying construct of cognitive decline. Test-retest reliability is also robust, provided the informant remains the same and the subject’s cognitive status has not rapidly progressed.

Factor Analysis

While the IQCODE is generally treated as a unidimensional scale measuring overall cognitive decline, factor analysis has sometimes been used to explore subdomains. Initial analyses often support a strong general factor, reinforcing its utility as a single mean screening score for dementia.

However, some research suggests potential sub-factors aligning with specific cognitive domains, such as memory/recall, executive function, and learned intellectual skills. Despite these findings, clinical and research standard practice emphasizes utilizing the total mean score across all items for initial screening, particularly when employing the widely adopted 16-item short form, which was developed and cross-validated by Jorm in 1994.

Instrument

Test Type: Informant-based rating scale, Screening instrument.

Format: 26-item questionnaire (full version) or 16-item short form. Responses are rated on a 5-point Likert scale ranging from “Much improved” to “Much worse.”

Language Available: Widely translated and validated in numerous languages globally.

Population Group: Caregivers or close associates of elderly individuals.

Age Group: Informants reporting on individuals typically aged 60 and above.

Population Details: Used across diverse populations, including those in community settings, primary care, and specialized Geriatric Psychiatry clinics, for screening purposes.

Test Methodology: The informant compares the subject’s current performance on 26 (or 16) daily activities to their performance 10 years ago. Items are scored from 1 (Much improved) to 5 (Much worse). A mean score is calculated, with higher scores indicating greater cognitive deterioration.

Keywords

IQCODE, Informant Report, Cognitive Impairment, Memory Assessment, Geriatric Medicine, Psychogeriatrics, Screening Tool, Jorm.

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Authors

Author ORCID Identifier: [N/A]

Affiliation Email addresses: [N/A]

Correspondence Address: [N/A]

Permissions & Fee and Test Year

The IQCODE was first published in 1989. It is generally considered a public domain instrument for non-commercial research and clinical use, making it widely accessible globally. The scale has been reviewed and standardized in major publications, including Ian McDowell’s 2006 guide to rating scales.

The original PDF of a related health measurement instrument, which includes the IQCODE, can be downloaded here: http://www.a4ebm.org/sites/default/files/Measuring%20Health.pdf

The original PDF of the short form can be downloaded here: https://www.alz.org/documents_custom/shortiqcode_english.pdf

Reference’s

• Jorm, A.F., Jacomb, P.A. (1989). The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): socio-demographic correlates, reliability, validity and some norms. Psychological Medicine, 19:1015–1022.
• Jorm, A.F., Scott, R., Jacomb, P.A. (1989). Assessment of cognitive decline in dementia by informant questionnaire. Int J Geriatr Psychiatry, 4:35–39.
• Jorm, A.F., Scott, R., Cullen, J.S., et al. (1991). Performance of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) as a screening test for dementia. Psychological Medicine, 21:785–790.
• Lewis, B., Harwood, D., Hope. T., et al. (1994). Can an informant questionnaire be used to predict the development of dementia in medical patients? Int J Geriatr Psychiatry, 4:941–945.
• Jorm, A.F. (1994). A short form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): development and cross validation. Psychological Medicine, 24:145–153.
• Jorm, A.F., Christensen, H., Korten, A.E., et al. (2000). Informant ratings of cognitive decline in old age: validation against change on cognitive tests over 7 to 8 years. Psychological Medicine, 30:981–985.
• Jorm, A.F. (2004). The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): a review. International Psychogeriatrics, 16:3, 1–19.
• McDowell, Ian. (2006). Measuring Health: A Guide to Rating Scales and Questionnaires, Third Edition. OXFORD UNIVERSITY PRESS.

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Items of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE)

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

Compared with 10 years ago how is this person at:

1. Recognizing the faces of family and friends
2. Remembering the names of family and friends
3. *Remembering things about family and friends, e.g., occupations, birthdays, addresses
4. *Remembering things that have happened recently
5. *Recalling conversations a few days later
6. Forgetting what he/she wanted to say in the middle of a conversation
7. *Remembering his/her address and telephone number
8. *Remembering what day and month it was
9. *Remembering where things are usually kept
10. *Remembering where to find things which have been put in a different place than usual
11. Adjusting to any change in his/her day-to-day routine
12. *Knowing how to work familiar machines around the house
13. *Learning to use a new gadget or machine around the house
14. *Learning new things in general
15. Remembering things that happened to him/her when he/she was young
16. Remembering things he/she learned when he/she was young
17. Understanding the meaning of unusual words
18. Understanding magazine or newspaper articles
19. *Following a story in a book or on TV
20. Composing a letter to friends or for business purposes
21. Knowing about important historical events of the past
22. *Making decisions on everyday matters
23. *Handling money for shopping
24. *Handling financial matters, e.g. the pension, dealing with the bank
25. *Handling other everyday arithmetic problems, e.g., knowing how much food to buy, knowing how long between visits from family or friends
26. *Using his/her intelligence to understand what’s going on and to reason things through.

* short form

Response Options:

• Much improved
• A bit improved
• Not much change
• A bit worse
• Much worse