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), including its validated Dutch adaptation (Nederlandse Informantvragenlijst over Cognitieve achteruitgang bij ouderen), represents one of the most widely implemented and rigorously validated collateral-source screening instruments in neuropsychology and geriatric medicine. Originally developed by Anthony F. Jorm and Patricia A. Jacomb in 1989, and adapted into Dutch by Jos F. M. de Jonghe and Ben Schmand in 1996, the instrument quantifies cognitive changes relative to an individual’s own baseline functioning over a designated 10-year window. Rather than administering performance-based cognitive tests directly to an older adult—which are notoriously vulnerable to confounding by premorbid intelligence, formal education level, test anxiety, physical frailty, and linguistic or socio-cultural background—the IQCODE relies on a knowledgeable proxy or informant (such as a spouse, adult child, or primary caregiver) to evaluate changes across everyday cognitive, functional, and instrumental activities of daily living (IADLs).

The scale was initially constructed as a 39-item questionnaire, later refined into a standard 26-item long version, an abbreviated 16-item short form (Short-IQCODE), and an ultra-brief 8-item screener. Each item is rated on a 5-point Likert-type response scale ranging from 1 (Much improved) through 3 (Not much change) to 5 (Much worse). Scoring generates an average item index between 1.00 and 5.00, wherein values exceeding 3.00 denote progressive cognitive deterioration. Psychometric evaluations across international and Dutch clinical cohorts establish exceptional internal consistency (Cronbach’s alpha typically ranging between .93 and .97), high test-retest reliability ($r > .80$), and remarkable diagnostic accuracy for distinguishing healthy cognitive aging from mild cognitive impairment (MCI) and neurodegenerative syndromes such as Alzheimer’s disease and vascular dementia (receiver operating characteristic areas under the curve frequently spanning .85 to .95). This comprehensive review delineates the historical development, psychometric foundations, theoretical framework, factorial architecture, and practical administration procedures of the scale.

Keywords

IQCODE, Informant Questionnaire on Cognitive Decline in the Elderly, collateral screening, dementia screening, cognitive decline, Alzheimer’s disease, mild cognitive impairment, proxy assessment, psychometrics, Dutch validation, geriatric neuropsychology, instrumental activities of daily living

Authors

The IQCODE was conceptualized, constructed, and psychometrically operationalized by Australian neuropsychologists and epidemiologists, with subsequent cross-cultural translation and rigorous clinical validation conducted by Dutch clinical neuropsychologists:

• Anthony F. Jorm, PhD, DSc: NHMRC Senior Principal Research Fellow and Emeritus Professor at the Melbourne School of Population and Global Health, University of Melbourne, Australia. Professor Jorm is an internationally recognized psychiatric epidemiologist whose foundational research established the necessity of longitudinal, within-person change metrics to circumvent educational and cultural biases inherent to traditional direct psychometric testing.
• Patricia A. Jacomb: Co-developer and research statistician at the Social Psychiatry Research Unit, Australian National University, Canberra, Australia. Jacomb collaborated extensively on the original psychometric calibration, item reduction analyses, and reliability assessments of the initial 39- and 26-item forms.
• Jos F. M. de Jonghe, PhD: Clinical Neuropsychologist at the Department of Old Age Psychiatry, Medical Centre Alkmaar (now Noordwest Ziekenhuisgroep), The Netherlands. Dr. de Jonghe led the cultural adaptation, linguistic validation, and multi-center clinical validation of the Dutch version (Nederlandse Informantvragenlijst over Cognitieve achteruitgang bij ouderen).
• Ben Schmand, PhD: Emeritus Professor of Clinical Neuropsychology at the University of Amsterdam and Amsterdam University Medical Centers (Amsterdam UMC), The Netherlands. Professor Schmand’s contributions advanced the diagnostic utility, normative standardization, and discriminative validity of informant reports across memory clinics and population-based cohorts in the Low Countries.

Purpose

The fundamental clinical and epidemiological purpose of the Informant Questionnaire on Cognitive Decline in the Elderly is to provide an objective, reliable, and standardized measurement of an older person’s longitudinal cognitive trajectory over a designated 10-year epoch, independent of formal cognitive testing performance. In routine clinical practice, screening for neurodegenerative diseases has traditionally relied on objective cross-sectional instruments such as the Mini-Mental State Examination (MMSE) or the Montreal Cognitive Assessment (MoCA). Although these direct assessment tools remain invaluable, they suffer from substantial methodological limitations:

• Premorbid Intellectual and Educational Confounding: Direct cognitive tests exhibit high correlations with formal education, socioeconomic status, literacy, and baseline intelligence quotient (IQ). High-functioning individuals may score within the normal range despite clinically significant neurodegeneration (yielding false-negative results), whereas individuals with limited literacy, low educational attainment, or intellectual disabilities frequently score below pathological thresholds in the absence of acquired dementia (yielding false-positive results).
• Cultural, Linguistic, and Ethnic Disparities: Most performance-based cognitive screeners contain semantic, linguistic, and cultural idioms that penalize ethnic minority populations, immigrant communities, and non-native speakers.
• Sensory, Physical, and Affective Interferences: Acute medical conditions, severe hearing loss, visual impairment, motor paralysis (e.g., post-stroke hemiparesis), severe systemic frailty, performance anxiety, or acute delirium can depress performance on direct cognitive tests, generating an inaccurate clinical portrait of chronic dementia.
• Test Resistance, Apathy, and Severe Agitation: Patients with advanced dementia, severe anosognosia (lack of insight), or behavioral and psychological symptoms of dementia (BPSD) frequently refuse to complete direct testing batteries or become uncooperative under examination conditions.

The IQCODE overcomes these obstacles by systematically capturing collateral observations from a close family member, spouse, or dedicated caregiver who has had continuous contact with the individual over the preceding decade. Because the informant is explicitly instructed to judge the patient’s current capacity in comparison to their own baseline performance 10 years prior, the subject serves as their own internal control. Consequently, a retired academic professor who has lost the ability to manage complex investments is flagged for significant deterioration, even if their cross-sectional verbal memory score remains superficially average; conversely, a lifelong manual laborer with minimal formal schooling who has always possessed rudimentary arithmetic skills is not pathologized if their day-to-day competency has remained stable.

In epidemiological research, the IQCODE serves as a high-throughput screening tool to estimate dementia incidence and prevalence in large cohort studies where direct clinical examinations are cost-prohibitive or unfeasible. In acute hospital settings, geriatric consultation-liaison services deploy the instrument to differentiate pre-existing, underlying chronic dementia from superimposed acute delirium, directly informing post-discharge planning and etiology-driven interventions.

Psychological Construct

The psychological construct measured by the IQCODE is intra-individual acquired cognitive decline, specifically manifest in everyday functional-cognitive competence. Rather than conceptualizing cognition as an isolated set of artificial laboratory abilities, the instrument operationalizes cognitive functioning as a dynamic, ecologically grounded behavioral competence across several interrelated cognitive sub-domains:

1. Anterograde and Episodic Memory

Episodic memory loss represents the hallmark neuropsychological feature of early Alzheimer’s pathology, reflecting initial neurofibrillary degeneration within the transentorhinal cortex and hippocampus. The IQCODE extensively probes this domain across multiple ecological modalities:

• Short-term anterograde retention: Remembering things that have occurred recently (Item 4) and recalling conversations a few days later (Item 5).
• Prospective and working memory: Forgetting what one wanted to say in the middle of a sentence or conversation (Item 6).
• Topographical and spatial memory: Remembering where common items are usually stored (Item 9) and searching for items that have been displaced to novel locations (Item 10).

2. Semantic Memory and Remote Knowledge Retrieval

In contrast to acute anterograde failure, crystallized semantic knowledge and remote retrograde autobiographical memories are typically preserved into mid-stage neurodegeneration. Items measuring this construct serve as critical benchmarks of disease progression and global impairment:

• Social semantic information: Recognizing the faces of lifelong acquaintances (Item 1), recalling names of family and close friends (Item 2), and remembering biographical details such as birthdays, family addresses, and occupations (Item 3).
• Remote personal and historical memory: Remembering events from youth (Item 15), school subjects or poems learned in early life (Item 16), and broad knowledge regarding historical events of public significance (Item 21).
• Lexical and language comprehension: Understanding the definitions of low-frequency or unusual vocabulary words (Item 17).

3. Executive Functioning, Fluid Reasoning, and Cognitive Flexibility

Frontostriatal and executive circuits govern an individual’s capacity to adapt to environmental disruption, organize goal-directed activity, and formulate abstract logical inferences. Deficits in this domain are captured through items addressing daily adaptation:

• Cognitive flexibility: Adjusting smoothly to unforeseen disruptions in daily routines (Item 11).
• Complex daily decision-making: Formulating practical, rational judgments regarding domestic and personal affairs (Item 22).
• Fluid reasoning and conceptual problem-solving: Utilizing analytical intelligence to comprehend novel situations, perceive causal links, and deduce solutions to real-world challenges (Item 26).

4. Instrumental Activities of Daily Living (Cognitive-IADLs)

Instrumental activities represent complex functional milestones that require the synchronized integration of memory, visual-spatial skill, executive planning, and numerical literacy. The IQCODE targets both familiar and newly acquired procedural skills:

• Procedural competence: Operating established household appliances (Item 12), acquiring the procedural steps needed to navigate new consumer gadgets or appliances (Item 13), and assimilating novel skills in general (Item 14).
• Complex communication: Composing coherent, syntactically organized correspondence or business letters (Item 20) and tracking continuous narrative structures in literature or television programming (Item 19).
• Financial numeracy and handling funds: Managing direct cash transactions during retail transactions (Item 23), orchestrating complex banking affairs, pensions, and bill payments (Item 24), and resolving daily numerical estimations, such as estimating grocery volumes or calculating inter-visit time intervals (Item 25).

Theoretical Framework

The theoretical framework underpinning the IQCODE is situated at the intersection of cognitive aging psychology, classical test theory, and proxy-informant methodology. Understanding the architecture of the IQCODE necessitates reviewing three foundational theoretical paradigms:

1. The Intra-Individual Discrepancy Paradigm

Traditional cognitive assessments operate under the normative psychometric model of differential psychology, comparing an individual’s raw score against a cross-sectional normative distribution matched by age and occasionally education. This approach incorporates a structural limitation: it relies on static between-subject variance to estimate a dynamic within-subject neurobiological change. Jorm and Jacomb recognized that neurodegenerative disorders do not represent low cognitive status; rather, they represent an acquired negative velocity—a progressive departure from an individual’s idiosyncratic baseline.

By shifting the frame of reference from inter-individual to intra-individual comparison, the IQCODE operationalizes dementia as relative functional decrement. The latent trait under investigation is not the general intelligence factor ($g$), but rather $\Delta g$ (the longitudinal vector of cognitive change over a ten-year window):

$$\text{Latent Construct} = \text{Cognitive Status}_{t_0} – \text{Cognitive Status}_{t_{-10}}$$

When an informant estimates change relative to a decade prior, the participant’s own prior ability serves as the reference intercept. Consequently, the correlation between IQCODE scores and premorbid intellectual markers (such as the National Adult Reading Test [NART] or years of formal schooling) is virtually zero ($r \approx .00$ to $.08$), whereas direct screening batteries correlate robustly with education ($r \approx .35$ to $.55$).

2. The Proxy-Informant Observation Model

The theoretical validity of proxy reporting rests upon the ecological sampling hypothesis. Direct formal assessments extract a brief, cross-sectional sample (e.g., 10 to 45 minutes) of an individual’s cognitive performance under high-stress, unfamiliar testing environments. In contrast, an observant cohabitant or close relative draws upon a continuous, longitudinal repository of thousands of cognitive trials enacted across real-world, naturalistic conditions—ranging from culinary preparation and conversational exchange to financial management.

This collateral paradigm directly addresses the neurocognitive phenomenon of anosognosia. Patients with progressive cortical dementia (most notably frontotemporal degeneration and moderate Alzheimer’s disease) often lose the metacognitive capacity to appraise their own functional decline, rendering self-report inventories fundamentally unreliable. The proxy-informant functions as an external, objective monitoring system, documenting the gradual erosion of cognitive schemas that the patient is neurologically incapable of perceiving.

3. Informant Variance and Attribution Theory

Psychometric theorists note that informant ratings do not represent perfectly transparent windows into patient status; they are mediated by the informant’s own cognitive, affective, and psychological filters. Informant variance can be modeled as:

$$\text{Observed Score} = \text{True Cognitive Decline} + \text{Informant Characteristic Bias} + \text{Measurement Error}$$

Psychometric investigations into the IQCODE have systematically explored three potential sources of collateral bias:

• Informant Affect: High caregiver burden, distress, or clinical depression in the informant can generate a negative halo effect, slightly elevating IQCODE scores (perceiving more severe deterioration).
• Informant Personality: Informant neuroticism can modestly influence ratings, whereas agreeableness fosters more charitable appraisals of functional autonomy.
• Contact Frequency and Relationship Type: Spousal informants, who share daily living spaces, frequently detect subtle early executive and prospective memory errors earlier than adult children who maintain intermittent, weekly contact.

Despite these psychological mediators, empirical structural equation modeling demonstrates that true patient cognitive decline accounts for the overwhelming proportion of the variance in IQCODE scores, validating the proxy-informant paradigm as a sound clinical measurement model.

Validity

The validity of the IQCODE and its Dutch version (Nederlandse Informantvragenlijst over Cognitieve achteruitgang bij ouderen) has been established across hundreds of international investigations, clinical trials, and epidemiological surveys.

Criterion and Diagnostic Validity

Diagnostic validity has been calibrated against clinical reference criteria, including the DSM-III-R, DSM-IV, and DSM-5 criteria for Major Neurocognitive Disorder, as well as the NINCDS-ADRDA consensus criteria for probable Alzheimer’s disease. In the benchmark Dutch validation study conducted by de Jonghe and Schmand (1996), the IQCODE demonstrated outstanding discriminative power in differentiating community-dwelling older adults from patients diagnosed with clinical dementia:

• Area Under the ROC Curve (AUC): In clinical validation samples, the ROC curve for the 26-item Dutch version ranges between .90 and .96, indicating exceptional overall diagnostic precision.
• Sensitivity and Specificity: Utilizing standard diagnostic cutoffs (typically an item mean score between 3.38 and 3.60), the 26-item IQCODE yields sensitivity levels ranging from 82% to 93% and specificity levels ranging from 80% to 92%. In memory clinic populations, an optimal cut-off score of 3.40 yields balanced sensitivity (88%) and specificity (85%).
• Detection of Mild Cognitive Impairment (MCI): For subtle prodromal stages (amnestic and non-amnestic MCI), lower cutoff thresholds (e.g., 3.15 to 3.25) provide optimal sensitivity (75% to 82%), although specificity is lower than when differentiating overt dementia.

Convergent and Concurrent Validity

Convergent validity has been evaluated by correlating IQCODE ratings with formal performance-based cognitive tests. Across dozens of published cohorts, the IQCODE correlates moderately to strongly with traditional psychometric instruments:

• Mini-Mental State Examination (MMSE): Pearson correlation coefficients consistently range between $r = -.50$ and $r = -.78$ (the negative sign reflecting that higher IQCODE scores indicate deterioration, whereas higher MMSE scores indicate preserved capacity).
• Cambridge Examination for Mental Disorders of the Elderly (CAMCOG): Correlations consistently reach $r = -.60$ to $r = -.72$.
• Clinical Dementia Rating (CDR) Scale: Strong convergent correlations ($r = .65$ to $.82$) are observed between the IQCODE item mean and the CDR Sum of Boxes.
• Objective Memory and Executive Batteries: IQCODE sub-domains demonstrate significant alignment with domain-specific neuropsychological tests, including the Rey Auditory Verbal Learning Test (RAVLT), the Trail Making Test (Part B), and the Stroop Color and Word Test.

Discriminant Validity and Independence from Premorbid Confounders

A primary psychometric advantage of the IQCODE over direct patient testing is its discriminant validity regarding educational and demographic variables. Meta-analytic findings indicate:

• Correlation with Education: Whereas MMSE scores correlate significantly with total years of schooling ($r = .30$ to $.50$), the correlation between the IQCODE and formal education is negligible ($r = -.02$ to $-.08$), confirming that the tool does not penalize individuals with limited literacy or educational access.
• Correlation with Premorbid IQ: Premorbid ability estimations (e.g., Dutch Adult Reading Test / NART) show zero-order correlations with IQCODE scores ($r = -.04$, $p > .05$).
• Discriminant Validity against Geriatric Depression: Although the presence of severe depression in the patient can cause mild executive slowing, the IQCODE discriminates well between primary Major Depressive Disorder (pseudodementia) and progressive neurodegenerative dementia, because depressive cognitive inertia tends to show a fluctuating course rather than the unrelenting 10-year functional decline characteristic of dementia.

Reliability

The reliability parameters of both the original English version and the Dutch adaptation demonstrate high statistical robustness across multiple reliability paradigms:

Internal Consistency

The scale exhibits very high internal consistency, reflecting a unified underlying latent dimension of perceived cognitive deterioration:

• 26-Item Long Form: Cronbach’s alpha coefficient ($lpha$) regularly spans between .95 and .97 across both clinical memory clinic cohorts and general population-based geriatric samples. In the Dutch normative and clinical cohorts evaluated by de Jonghe and Schmand, Cronbach’s alpha was documented at .96.
• 16-Item Short Form: Cronbach’s alpha remains between .93 and .95, demonstrating that psychometric reliability is fully preserved despite the removal of 10 items.
• Item-Total Correlations: Corrected item-total correlations across the 26 items are consistently strong, with virtually all items exceeding $r = .55$, and prominent items (such as remembering recent events, handling finances, and general intelligence) exceeding $r = .75$.

Test-Retest Reliability

The temporal stability of informant appraisals on the IQCODE has been verified across short-term and medium-term re-administration intervals:

• Short-Term Stability (2 to 4 Weeks): In stable community cohorts, test-retest reliability intraclass correlation coefficients (ICC) range from .94 to .98, demonstrating that informant evaluations are stable and free from random short-term measurement error.
• Medium-Term Stability (2 to 6 Months): In patients without progressive neurological decline, test-retest correlation coefficients remain high ($r = .75$ to $.88$). In neurodegenerative cohorts, scores show a predictable, progressive increase over 1- to 2-year longitudinal follow-ups, tracking neurobiological disease progression.

Inter-Rater (Inter-Informant) Reliability

An essential psychometric consideration for any collateral rating system is whether different informants provide concordant evaluations of the same individual. Studies administering the IQCODE simultaneously to two independent informants (e.g., comparing ratings provided by a spouse with those provided by an adult child) demonstrate inter-rater reliability coefficients ranging from $r = .65$ to $r = .82$ ($p < .001$). Discrepancies are typically attributable to differences in contact frequency, with the primary daily cohabitant reporting higher sensitivity to subtle domestic executive errors.

Factor Analysis

The dimensional structure of the IQCODE has been evaluated extensively using both exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) across diverse international and clinical populations.

Exploratory Factor Analysis (EFA)

In the original structural investigations conducted by Jorm and Jacomb (1989), principal component analysis (PCA) revealed an overwhelming, dominant first general factor accounting for approximately 50% to 62% of the total scale variance. The eigenvalue for this primary general cognitive decline factor consistently dwarfs subsequent components (eigenvalues frequently exceeding 12.0 to 14.0, while secondary components drop below 1.5). This empirical finding provided the mathematical justification for using a single composite average score (mean item score) in both clinical practice and research.

When oblique or orthogonal rotations (such as Promax or Varimax) are applied to extract minor multidimensional facets, three distinct yet highly inter-correlated sub-factors routinely emerge:

• Factor 1: Anterograde and Everyday Memory: High factor loadings (.68 to .85) for Item 4 (recent events), Item 5 (conversations), Item 7 (address/telephone number), Item 8 (day and month), and Item 9 (location of objects).
• Factor 2: Executive Control, Fluid Reasoning, and Cognitive-IADLs: Substantial loadings (.60 to .82) for Item 11 (routine adjustment), Item 22 (daily decisions), Item 23 (money for shopping), Item 24 (complex financial affairs), and Item 26 (using intelligence to reason).
• Factor 3: Crystallized Semantic and Remote Autobiographical Memory: Modest to strong loadings (.52 to .74) for Item 1 (recognizing faces), Item 2 (recalling names), Item 15 (events from youth), Item 16 (knowledge learned when young), and Item 17 (meaning of words).

Confirmatory Factor Analysis (CFA) and Bi-Factor Modeling

Modern psychometric re-evaluations utilizing structural equation modeling (SEM) and item response theory (IRT) demonstrate that a bi-factor model best fits the covariance matrix of the 26-item instrument. Under this bi-factor specification:

• A single overarching, general factor of Global Cognitive Decline directly accounts for the vast majority of common variance (Omega Hierarchical, $\omega_h > .88$).
• Specific group factors (Memory, Executive/Functional IADLs, Semantic/Language) explain minor residual variance but do not provide reliable independent subscale scores beyond the global score.
• Model Fit Indices: CFA evaluations of the unidimensional and bi-factor structures confirm acceptable to excellent fit criteria in both Dutch and international samples: Comparative Fit Index ($CFI > .95$), Tucker-Lewis Index ($TLI > .94$), Root Mean Square Error of Approximation ($RMSEA < .06$, 90% CI [.048, .068]), and Standardized Root Mean Square Residual ($SRMR < .05$).

These factorial findings validate the practice established by de Jonghe, Schmand, and Jorm: computing and interpreting the mean global item score as a valid unidimensional index of neurocognitive decline.

Instrument / Measurement Tool

The structural, operational, and scoring parameters of the Informant Questionnaire on Cognitive Decline in the Elderly are detailed below:

• Test Classification: Collateral-source / Proxy-informant behavioral rating questionnaire.
• Target Population: Older adults (typically aged 65 years and older) presenting with subjective cognitive complaints, suspected mild cognitive impairment, acute confusion, or progressive neurodegenerative dementia.
• Respondent (Informant) Eligibility: A spouse, adult offspring, sibling, close companion, or professional primary caregiver who has maintained regular, close personal contact with the patient over the preceding 10 years (minimum required contact: typically several days per month, ideally cohabiting or weekly visits).
• Temporal Frame of Reference: A 10-year retrospective comparison window (comparing the patient’s current daily competence to their functioning 10 years prior).
• Scale Versions:
  • Standard Long Version: 26 items (the primary instrument detailed herein).
  • Short Version (Short-IQCODE): 16 items, constructed to optimize efficiency in acute medical, emergency, and general practice consultations.
  • Ultra-Brief Version: 8 items, occasionally utilized in broad epidemiological health surveys.
• Administration Format: Self-administered paper-and-pencil questionnaire, clinician-administered structured interview, or secure digital web-based questionnaire. Total completion time spans approximately 5 to 10 minutes.
• Response Scale: A balanced, 5-point Likert-type scale containing an explicit midpoint of no change:
  • 1 = Much improved
  • 2 = A bit improved
  • 3 = Not much change
  • 4 = A bit worse
  • 5 = Much worse
• Scoring Algorithm:
  • Each item is scored on an integer continuum from 1 to 5.
  • Total Sum Score: Sum of all item ratings completed (for 26 items, range = 26 to 130).
  • Mean Item Score (Standard Recommended Score): Calculated by dividing the sum of all answered items by the total number of items completed:
    $$\text{IQCODE Mean Score} = \frac{\sum \text{Completed Item Ratings}}{N_{\text{completed items}}}$$
  • This generates a continuous metric ranging from 1.00 to 5.00.
  • Handling Missing Data: If an informant cannot answer an item (e.g., the subject never engaged in handling money or letters), that item is omitted, and the denominator is adjusted accordingly. The overall score remains valid provided at least 80% of items are completed.
• Clinical Interpretation and Diagnostic Cutoffs:
  • Score = 3.00: Indicates cognitive stability (no perceived change relative to 10 years prior).
  • Score < 3.00: Indicates perceived cognitive improvement (uncommon in geriatric evaluations, occasionally noted following the resolution of acute medical illnesses or successful treatment of depression).
  • Score > 3.00: Denotes cognitive deterioration.
  • Cutoff 3.31 to 3.38: High sensitivity screener; flags possible early cognitive decline or mild cognitive impairment (MCI). Suitable for secondary memory clinic triage.
  • Cutoff 3.40 to 3.60: Standard clinical threshold optimized for balanced sensitivity and specificity in detecting clinical dementia (DSM/NINCDS-ADRDA criteria).
  • Score > 4.00: Severe, extensive functional and cognitive deterioration across multiple daily domains.

Permissions & Fee and Test Year

• Publication Years:
  • Original 39- and 26-item English IQCODE: 1989 (Anthony F. Jorm & Patricia A. Jacomb).
  • Short 16-item English IQCODE: 1994 (Anthony F. Jorm).
  • Validated Dutch Translation (Nederlandse Informantvragenlijst over Cognitieve achteruitgang bij ouderen): 1996 (Jos F. M. de Jonghe & Ben Schmand).
• Copyright and Access Policy: The IQCODE was placed in the public domain for academic, clinical, and non-commercial scientific research by its developers. No licensing fees or royalty payments are required to administer, reproduce, or score the instrument for clinical diagnostic or academic investigation.
• Availability and Permissions: The English instrument, its translated variants, and scoring guides are openly accessible through academic publications and institutional repositories, including the Australian National University and Dutch neuropsychological assessment handbooks. Commercial entities integrating the IQCODE into proprietary electronic medical software or commercial clinical trial platforms should contact the original authors and institutional copyright holders for formal administrative clearance.

References

• de Jonghe, J. F. M., & Schmand, B. (1996). De Nederlandse Informant Vragenlijst over Cognitieve Achteruitgang bij Ouderen (N-IQCODE) [The Dutch Informant Questionnaire on Cognitive Decline in the Elderly (N-IQCODE)]. Tijdschrift voor Gerontologie en Geriatrie, 27(6), 250–257.
• de Jonghe, J. F. M., Schmand, B., Ooms, M. E., & Ribbe, M. W. (1997). The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) in a Dutch nursing home population. International Journal of Geriatric Psychiatry, 12(1), 49–54. https://doi.org/10.1002/gps.930090709
• Jorm, A. F. (2004). The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): A review. International Psychogeriatrics, 16(3), 275–293. https://doi.org/10.1017/S1041610204000390
• 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(4), 1015–1022. https://doi.org/10.1017/S0033291700005742
• Jorm, A. F., Scott, R., Cullen, J. S., & MacKinnon, A. J. (1991). Performance of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) as a screening test for dementia. Psychological Medicine, 21(3), 785–790. https://doi.org/10.1017/S0033291700022418
• Quinn, T. J., Fearon, P., Noel-Storr, A. H., Young, C., McShane, R., & Stott, D. J. (2014). Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for the diagnosis of dementia in general hospital inpatients. Cochrane Database of Systematic Reviews, 2014(4), CD010771. https://doi.org/10.1002/14651858.CD010771.pub2

Items of the Scale