P1–283: Ethnic differences in MRI scans among Alzheimer's disease patients and unaffected siblings in the MIRAGE Study
Bibliographic record
Abstract
Degenerative brain changes associated with the AD process can often be detected by MRI scan. MRI may help identify individuals with incipient disease and delineate intermediate phenotypes for genetic analyses. MIRAGE is a family–based, multi–ethnic study which seeks to identify genetic and other risk factors for AD. To present initial MIRAGE family analyses and explore the utility of MRI for differentiating AD status and ethnic differences. 127 Caucasian (CA) and 30 African–American (AA) MIRAGE sibships with semi–quantitative MRI measures of brain atrophy and white matter hyperintensities (WMH) were analyzed. Analyses allowed for non–independent observations and missing data using generalized estimating equations which can accommodate correlated family data. For ordinal variables, continuation ratio models were used. Confounders (e.g. disease duration, gender, body mass index, and APOE ϵ4) of associations between MRI and diagnosis were evaluated. CA AD and non–demented siblings had mean ages at MRI of 75.1 ± 9.0 yrs and 71.7 ± 9.0 yrs, were 42% and 40% male, and were 68% and 42% APOE ϵ4 carriers, respectively. AA AD and non–demented siblings were similar in age, but differed by sex (28% and 29% male, respectively) and frequency of APOE ϵ4 carriers (81% and 66%, respectively) when compared to CA. AD association with brain atrophy was similar in both ethnic groups (CA: β =16.77±1.66, p<0.0001, AA: β = 17.05±3.14). Log–transformed measures of WMH were significantly elevated in AD patients, but differed by ethnic group (CA: β =1.25±0.20, p<0.0001, AA: β = 0.78 ± 0.28, p< 0.0001). Hippocampal atrophy was associated with AD, but differed by ethnicity (continuation ratio βCA=1.21 to 4.32, p< 0.003; βAA=1.70 to 3.68 in AA, p<0.03). Estimates were adjusted for familial dependencies. Disease duration and APOE ϵ4 confounding varied with ethnicity and MRI traits. MRI measures of brain atrophy and vascular disease differed substantially between AD subjects and their unaffected siblings. Estimates of association between AD and MRI measures may differ between Caucasian and African Americans. We identified a set of MRI factors that are suitable for genetic analyses. Future work will examine MRI traits and novel genes for AD by ethnicity.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".