Dutch Informant Questionnaire on Cognitive Decline in the Elderly / Informant Questionnaire on Cognitive Decline in the Elderly

Abstract

The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) is a widely utilized screening test designed for the early detection and assessment of dementia. It relies on an informant report to gauge changes in the daily functional and cognitive functioning of the patient over a significant period, typically the preceding 10 years. Originally developed with 39 items, the IQCODE has evolved to include various versions to suit clinical and research settings. The current standard versions include a modified long version (26 items), a widely used short version (16 items), and an ultra-short version (8 items). The Dutch adaptation is known as the Nederlandse Informantvragenlijst over Cognitieve achteruitgang bij ouderen.

Keywords

IQCODE, Informant Questionnaire, Cognitive Decline, Dementia Screening, Older Adults, Geriatric Assessment, Mental Functions, Memory Assessment, Psychometrics

Authors

Jorm AF, Jacomb PA (Original Development, 1989); de Jonghe JFM, Schmand B (Dutch Adaptation, 1996)

Purpose

The primary purpose of the IQCODE is to facilitate the identification of cognitive impairment, particularly early-stage dementia, in clinical and community settings where specialized cognitive testing may be impractical or unavailable. It is particularly valuable for differentiating between normal aging and pathological cognitive decline.

By focusing on observational changes reported by a reliable informant—such as a family member or caregiver—the IQCODE bypasses issues related to poor patient cooperation, language barriers, or patient insight that often complicate direct cognitive testing. The scale aims to quantify the magnitude of decline in daily activities and memory function relative to the individual’s performance 10 years prior.

Construct

The IQCODE measures the psychological construct of functional cognitive decline. This construct encompasses the observable deterioration in an individual’s ability to perform everyday tasks that require complex cognition, such as memory, orientation, judgment, language, and handling finances.

The underlying theory is that changes reported by a close associate reflect real-world functional impairment, which is a hallmark of progressive neurodegenerative conditions. The items specifically target domains of cognitive functioning, which fall under the category of Mental Functions. These changes are typically associated with psychological disorders, specifically dementias and other cognitive impairments found in older populations.

Validity

The IQCODE demonstrates strong validity across numerous studies globally. Criterion validity is high, with the scale showing strong correlations with clinical diagnoses of dementia and established standardized tests such as the Mini-Mental State Examination (MMSE) and the Clinical Dementia Rating (CDR) scale.

Discriminant validity is evidenced by the IQCODE’s effectiveness in distinguishing between individuals with dementia, those with mild cognitive impairment (MCI), and cognitively healthy older adults. Furthermore, the use of an informant report provides ecological validity, as the assessment reflects real-world functional status rather than performance in a contrived testing environment.

Reliability

The IQCODE is generally recognized for its excellent reliability. Internal consistency, measured by Cronbach’s alpha, typically ranges between 0.90 and 0.95 for both the long and short versions, indicating strong homogeneity among the items. This suggests that all items consistently measure the same underlying construct of cognitive decline.

Test-retest reliability is also robust, particularly when the informant remains the same, confirming the stability of the measurement over time. Inter-rater reliability, while generally good, can vary slightly depending on the informant’s relationship to the patient and their opportunity to observe the patient’s daily functioning.

Factor Analysis

Factor analysis studies of the IQCODE, including the 39-item and 26-item versions, consistently support a unidimensional factor structure. This means that the scale primarily measures a single dominant factor: global cognitive decline.

Although the items cover various aspects of daily function (e.g., memory, judgment, instrumental activities of daily living), the strong correlation among these items confirms that they load onto one overarching factor. This unidimensionality supports the use of a single total score as the primary metric for screening cognitive impairment.

Instrument

Test Type: Screening Questionnaire (Informant-based)

Format: Structured Questionnaire (Paper-and-pencil or interview administration)

Language Available: English (Original), Dutch (Nederlandse versie), and numerous other translations globally.

Population Group: Clinical and Community populations

Age Group: Older Adults (Ouderen)

Population Details: Individuals suspected of or diagnosed with cognitive impairment or dementia, requiring an objective assessment of functional change.

Test Methodology: The scale uses a five-point Likert scale (e.g., Much Better, A Little Better, No Change, A Little Worse, Much Worse) for the informant to rate the patient’s current functioning compared to their functioning 10 years ago. Scores are aggregated to provide a measure of decline.

The original Explanation Form (Toelichtingsformulier) for the Dutch version can be downloaded here: IQCODE-N-form.pdf.

The 16-item instrument version is available here: IQCODE-N-meetinstr-16-item.pdf.

The 26-item instrument version is available here: IQCODE-N-meetinstr-26-item.pdf.

Keywords

Functional Decline, Geriatric Psychiatry, Clinical Assessment, Jorm AF, Schmand B, Cognitive Screening, Psychometrics, Informant report, Memory

Authors

Author ORCID Identifier: N/A (Information not provided in source)

Affiliation Email addresses: N/A (Information not provided in source)

Correspondence Address: N/A (Information not provided in source)

Permissions & Fee and Test Year

The original IQCODE was first published in 1989 by Jorm AF and Jacomb PA. The widely used Dutch version was published in 1996 by de Jonghe JFM and Schmand B. The IQCODE is generally considered to be in the public domain and is often used without specific license fees for non-commercial research and clinical practice, although users should verify the current status with the primary authors or relevant institutions.

Reference’s

The primary references for the IQCODE are the foundational paper describing the original 39-item scale and the publication detailing the Dutch adaptation.

• Jorm AF, Jacomb PA. The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): reliability and validity of a one-page form for rating cognitive change in dementia. Psychological Medicine. 1989; 19(4):1013-21.

• de Jonghe JFM, Schmand B. Nederlandse Informantvragenlijst over Cognitieve achteruitgang bij ouderen (IQCODE). 1996.

Items of the Nederlandse Informantvragenlijst over Cognitieve achteruitgang bij ouderen / Informant Questionnaire on Cognitive Decline in the Elderly

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

The source content provides links to the official instrument documents, but the individual items are not listed here. For the full list of items in the 16-item and 26-item versions of the Nederlandse Informantvragenlijst over Cognitieve achteruitgang bij ouderen, please refer to the provided PDF documents linked in the Instrument section above.