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Validity and reliability of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for dementia assessment in rural South Africa
Muqi Guo, Tâmara P. Taporoski, Meagan T. Farrell, Nomsa Brightness Mahlalela, Brent Tipping, Adam M. Brickman, Jennifer J. Manly, Stephen Tollman et al.. Alzheimer s & Dementia, 2025-08-01
Topic: Risk, prevention and care in population studies
Index participants averaged 71.9 years, with > 50% lacking formal education. IQCODE missingness declined across waves and was associated with index participant characteristics. IQCODE scores were correlated with both index participant and informant characteristics. The 16-item IQCODE demonstrated a single-factor structure explaining up to 66% of variance, strong internal consistency, and correlations with word and story recall, indicating high convergent validity. IQCODE is a reliable, valid dementia assessment tool in rural South Africa, supporting broader African applications and cross-national comparisons. HIGHLIGHTS: Sixteen-item Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) responses in rural South Africa support a single-factor construct, explaining up to 66% of total observed variance. The single-factor structure is reliable, as the IQCODE items data show high internal consistency (omega hierarchical = 0.90). The IQCODE score shows strong convergent validity with significant correlation with word and story recall memory measures. Index participants' characteristics are mainly associated with IQCODE completion. IQCODE contributes to dementia assessment in rural South Africa and other settings with low education populations.
Key findings
- Index participants averaged 71.9 years, with > 50% lacking formal education.
- IQCODE missingness declined across waves and was associated with index participant characteristics.
- IQCODE scores were correlated with both index participant and informant characteristics.
- The 16-item IQCODE demonstrated a single-factor structure explaining up to 66% of variance, strong internal consistency, and correlations with word and story recall, indicating high convergent validity.
- IQCODE is a reliable, valid dementia assessment tool in rural South Africa, supporting broader African applications and cross-national comparisons.
Why it matters
This longitudinal study found that the 16-item IQCODE is a reliable and valid tool for dementia assessment in rural South Africa, including among people with low education. It supports use of this questionnaire in similar settings and for cross-national comparisons, but it is an assessment tool rather than a treatment, cure, or prevention.
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Study details
- Study designlongitudinal study
- Participants1,309
- Evidence strengthModerate
How this study scored 52/100
Published in a peer-reviewed journal, and it is a longitudinal study following the same people over time. Scored zero for effect reported and randomised / blinded because the record does not state it.
| Component | Points | Why |
|---|---|---|
| Journal tier | 7 / 10 | Tier 3 — peer-reviewed journal (Alzheimer s & Dementia) |
| Journal's citation record | 2 / 4 | Alzheimer s & Dementia: journal h-index 228 (OpenAlex, 2026-10-29) |
| Study design | 7 / 12 | A longitudinal study following the same people over time |
| Strength of evidence | 3 / 5 | Rated “moderate” in our summary |
| Peer-review validation | 10 / 10 | Peer-reviewed. Published as an article in a named peer-reviewed journal. |
| How recent | 4 / 5 | 2025 — within 3 year(s) of the newest study here |
| Sample size | 3 / 4 | 1,309 participants |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 3 / 3 | Studied in people (participant count stated) |
| Randomised / blinded | 0 / 2 | No randomisation or blinding stated — scores zero (not stated in the record — scored 0) |
| Times cited | 1 / 7 | Cited 2 times (OpenAlex, 2026-10-10) |
| Citations per year | 0 / 5 | 0.7 citations a year over 3 year(s) since 2025 |
| Impact for its field and year | 2 / 6 | Cited 1.3× the average for papers of its field and year (OpenAlex FWCI) |
| Cited by studies here | 0 / 6 | No other study in this library cites it |
| Still being cited | 0 / 4 | Cited 2 times in 2024–2026 (2026 still in progress; OpenAlex) |
| Senior author's track record | 1 / 4 | Last-listed author Darina T. Bassil: h-index 10 (OpenAlex, whole career) |
| Institution's track record | 3 / 3 | Harvard University: institution h-index 3,235 (OpenAlex) |
| Multi-centre collaboration | 2 / 3 | OpenAlex lists 7 institution(s) in 2 countries |
| Indexed in PubMed | 2 / 2 | Indexed in PubMed (PMID 40779424) |
| Free to read | 2 / 2 | Free to read |
| Total | 52 / 100 | — |
What each of these 20 components measures, and what this score is not →
Read the original
Full text: free to read — OpenAlex lists this copy as free to read: the link above (checked 6 Feb 1020).
Cite this study APA, Vancouver, BibTeX · download .bib or .ris
Built from the record alzhub holds for this paper, not looked up. Volume, issue and page numbers are not held in the record. The record's author list ends in “et al.”, so not every author is named. Check the citation against the original before you use it.
APA 7th
Guo, M., Taporoski, T. P., Farrell, M. T., Mahlalela, N. B., Tipping, B., Brickman, A. M., et al. (2025). Validity and reliability of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for dementia assessment in rural South Africa. Alzheimer s & Dementia. https://doi.org/10.1002/alz.70584
Vancouver
Guo M, Taporoski TP, Farrell MT, Mahlalela NB, Tipping B, Brickman AM, et al. Validity and reliability of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for dementia assessment in rural South Africa. Alzheimer s & Dementia. 2025. doi:10.1002/alz.70584. PMID: 40779424.
BibTeX
@article{guo2025-40779424,
author = {Guo, Muqi and Taporoski, Tâmara P. and Farrell, Meagan T. and Mahlalela, Nomsa Brightness and Tipping, Brent and Brickman, Adam M. and Manly, Jennifer J. and Tollman, Stephen and others},
title = {{Validity and reliability of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for dementia assessment in rural South Africa}},
journal = {Alzheimer s \& Dementia},
year = {2025},
doi = {10.1002/alz.70584},
pmid = {40779424},
url = {https://doi.org/10.1002/alz.70584}
}
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