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Intra-individual variability in Alzheimer's disease and cognitive aging: definitions, context, and effect sizes
Tractenberg RE, Pietrzak RH.. PloS one, 2011-04-19
Topic: Amyloid, tau and blood-test diagnosis
Background/aims To explore different definitions of intra-individual variability (IIV) to summarize performance on commonly utilized cognitive tests (Mini Mental State Exam; Clock Drawing Test); compare them and their potential to differentiate clinically-defined populations; and to examine their utility in predicting clinical change in individuals from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Methods Sample statistics were computed from ADNI cohorts with no cognitive diagnosis, a diagnosis of mild cognitive impairment (MCI), and a diagnosis of possible or probable Alzheimer's disease (AD). Nine different definitions of IIV were computed for each sample, and standardized effect sizes (Cohen's d) were computed for each of these definitions in 500 simulated replicates using scores on the Mini Mental State Exam and Clock Drawing Test.
Key findings
- Methods Sample statistics were computed from ADNI cohorts with no cognitive diagnosis, a diagnosis of mild cognitive impairment (MCI), and a diagnosis of possible or probable Alzheimer's disease (AD).
- Nine different definitions of IIV were computed for each sample, and standardized effect sizes (Cohen's d) were computed for each of these definitions in 500 simulated replicates using scores on the Mini Mental State Exam and Clock Drawing Test.
- IIV was computed based on test items separately ('within test' IIV) and the two tests together ('across test' IIV).
- The best performing definition was then used to compute IIV for a third test, the Alzheimer's Disease Assessment Scale-Cognitive, and the simulations and effect sizes were again computed.
Why it matters
This study explored different definitions of intra-individual variability on the Mini Mental State Exam and Clock Drawing Test and compared their ability to distinguish cognitive groups and predict change in ADNI participants. It is about cognitive measurement methods, not treating, curing, or preventing Alzheimer's disease.
Study details
- Evidence strengthLow
How this study scored 45/100
Published in a peer-reviewed journal. Scored zero for study design, sample size, effect reported, studied in people and randomised / blinded because the record does not state it.
| Component | Points | Why |
|---|---|---|
| Journal tier | 7 / 10 | Tier 3 — peer-reviewed journal (PloS one) |
| Journal's citation record | 4 / 4 | PLoS ONE: journal h-index 594 (OpenAlex, 2026-10-29) |
| Study design | 0 / 12 | No study design recorded — scores zero, not guessed (not stated in the record — scored 0) |
| Strength of evidence | 1 / 5 | Rated “low” in our summary |
| Peer-review validation | 10 / 10 | Peer-reviewed. Published as an article in a named peer-reviewed journal. |
| How recent | 1 / 5 | 2011 — within 20 year(s) of the newest study here |
| Sample size | 0 / 4 | Participant count not stated — scores zero (not stated in the record — scored 0) |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 0 / 3 | Not stated whether this was studied in people — scores zero (not stated in the record — scored 0) |
| Randomised / blinded | 0 / 2 | No randomisation or blinding stated — scores zero (not stated in the record — scored 0) |
| Times cited | 4 / 7 | Cited 66 times (OpenAlex, 2026-10-10) |
| Citations per year | 2 / 5 | 3.9 citations a year over 17 year(s) since 2011 |
| Impact for its field and year | 2 / 6 | Cited 2.6× the average for papers of its field and year (OpenAlex FWCI) |
| Cited by studies here | 1 / 6 | Cited by 2 other studies in this library |
| Still being cited | 2 / 4 | Cited 22 times in 2024–2026 (2026 still in progress; OpenAlex) |
| Senior author's track record | 3 / 4 | Last-listed author Robert H. Pietrzak: h-index 94 (OpenAlex, whole career) |
| Institution's track record | 2 / 3 | Yale University: institution h-index 1,927 (OpenAlex) |
| Multi-centre collaboration | 2 / 3 | OpenAlex lists 4 institution(s) in 1 country |
| Indexed in PubMed | 2 / 2 | Indexed in PubMed (PMID 21526188) |
| Free to read | 2 / 2 | Free to read |
| Total | 45 / 100 | — |
What each of these 20 components measures, and what this score is not →
Read the original
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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. Check the citation against the original before you use it.
APA 7th
Tractenberg, R. E., & Pietrzak, R. H. (2011). Intra-individual variability in Alzheimer's disease and cognitive aging: definitions, context, and effect sizes. PloS one. https://doi.org/10.1371/journal.pone.0016973
Vancouver
Tractenberg RE, Pietrzak RH. Intra-individual variability in Alzheimer's disease and cognitive aging: definitions, context, and effect sizes. PloS one. 2011. doi:10.1371/journal.pone.0016973. PMID: 21526188.
BibTeX
@article{tractenberg2011-21526188,
author = {Tractenberg, R. E. and Pietrzak, R. H.},
title = {{Intra-individual variability in Alzheimer's disease and cognitive aging: definitions, context, and effect sizes}},
journal = {PloS one},
year = {2011},
doi = {10.1371/journal.pone.0016973},
pmid = {21526188},
url = {https://doi.org/10.1371/journal.pone.0016973}
}
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