Older Adults’ Drop in Cerebral Oxygenation on Standing Correlates With Postural Instability and May Improve With Sitting Prior to Standing
Bibliographic record
Abstract
BACKGROUND: Impaired blood pressure (BP) recovery with orthostatic hypotension on standing occurs in 20% of older adults. Low BP is associated with low cerebral blood flow but mechanistic links to postural instability and falls are not established. We investigated whether posture-related reductions in cerebral tissue oxygenation (tSO2) in older adults impaired stability upon standing, if a brief sit before standing improved tSO2 and stability, and if Low-tSO2 predicted future falls. METHOD: Seventy-seven older adults (87 ± 7 years) completed (i) supine-stand, (ii) supine-sit-stand, and (iii) sit-stand transitions with continuous measurements of tSO2 (near-infrared spectroscopy). Total path length (TPL) of the center of pressure sway quantified stability. K-cluster analysis grouped participants into High-tSO2 (n = 62) and Low-tSO2 (n = 15). Fall history was followed up for 6 months. RESULTS: Change in tSO2 during supine-stand was associated with increased TPL (R = -.356, p = .001). When separated into groups and across all transitions, the Low-tSO2 group had significantly lower tSO2 (all p < .01) and poorer postural stability (p < .04) through 3 minutes of standing compared to the High-tSO2 group. There were no effects of transition type on tSO2 or TPL for the High-tSO2 group, but a 10-second sitting pause improved tSO2 and enhanced postural stability in the Low-tSO2 group (all p < .05). During 6-month follow-up, the Low-tSO2 group had a trend (p < .1) for increased fall risk. CONCLUSIONS: This is the first study to show an association between posture-related cerebral hypoperfusion and quantitatively assessed instability. Importantly, we found differences among older adults suggesting those with lower tSO2 and greater instability might be at increased risk of a future fall.
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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 | 0.000 | 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".