Differential impact of obstructive sleep apnea on hippocampal structure in late middle‐aged and older women and men
Bibliographic record
Abstract
Abstract Background Recent studies have suggested that obstructive sleep apnea (OSA) could be a modifiable risk factor for dementia. Consequently, efforts have been made to better understand the role of OSA on brain structure integrity, but results between studies are inconsistent. Discrepancies could be partly due to moderating factors (e.g., sex) or complex physiological mechanisms (e.g., oedema) that blur the association between OSA and brain structure. Here, we investigated the association between OSA severity and hippocampal grey matter volume in women and men. We also performed free‐water fraction analyses to understand how oedema could impact hippocampal volumes. Method Seventy‐three men (age: 65.47±7.22 years; apnea‐hypopnea index [AHI]: 15.52±16.14 events/h; 31 with mild cognitive impairments [MCI]) and 47 women (age: 71.11 ± 6.65; AHI: 11.56 ± 9.92; 22 with MCI) underwent an overnight polysomnography, a neuropsychological evaluation and a magnetic resonance imaging session. Using the hippocampal subfield module in Freesurfer 7.1, total bilateral hippocampal volumes were extracted and normalised to the total intracranial volume. Diffusion data was preprocessed using TractoFlow‐ABS, and Freewater‐Flow and the Sherbrooke Connectivity Imaging Lab scripts were used to extract bilateral hippocampal free‐water fraction. Controlling for age and cognitive status, sex‐stratified linear regressions were performed between (i) the bilateral hippocampal volume or (ii) Free‐water‐corrected bilateral hippocampal volume and log‐transformed AHI. Result In women, we observed a positive association between the AHI and bilateral hippocampal volumes (r=0.414; p=0.005), where more severe OSA was associated with higher volumes. This association was not observed in men (p=0.427). When using the free‐water corrected volumes, this association was no longer significant in women (p=0.481), suggesting that the increased hippocampal volume could be due to OSA‐related cytotoxic (intracellular) oedema. Conclusion In this cohort, while men’s hippocampal volume was unaffected by OSA, women with OSA presented hippocampal hypertrophy likely due to intracellular oedema. Cytotoxic oedema is a known precursor to vasogenic (extracellular) oedema and cell death, suggesting that women might be more vulnerable to the cerebral consequences of OSA than men. Since women have a higher lifetime risk of developing Alzheimer's disease, future studies on OSA should pay a particular attention to women.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
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".