Correlates of white matter hyperintensities in Royal Canadian Air Force pilots and aircrew
Bibliographic record
Abstract
BACKGROUND: Military aircrew can be exposed to extreme occupational and physiological stressors, such as extreme G-forces, decompression stress, and intermittent hypoxia and/or hyperoxia. These stressors may contribute to cognitive dysfunction and neurobiological damage. Previous studies on U.S. Air Force U-2 pilots found a higher burden of white matter hyperintensities (WMH) on MRI, commonly associated with cerebrovascular disease, were linked to lower cognitive test performance in otherwise healthy, highly functioning individuals. Prompted by findings in U-2 pilots, we investigated the prevalence and neurocognitive correlates of WMH in Royal Canadian Air Force (RCAF) fighter pilots and aircrew. METHOD: All study participants were Canadian Armed Forces personnel, including 42 high performance aircraft pilots and 6 high altitude, non-pilot aircrew. Prior to testing, detailed medical, environmental and occupational exposure histories were acquired. The testing included brain MRI (3T) and neurocognitive assessments. A standardized and validated volumetric image segmentation algorithm was used to acquire WMH and enlarged perivascular spaces (PVS). The Mann-Whitney U test was used to compare RCAF WMH volumes with a convenience sample of 12 age-matched normal controls from a previous scan-rescan study. Regression models were used to examine associations between WMH and PVS with neurocognitive test performance in the RCAF study participants. RESULT: The RCAF group had a higher mean volume of WMH compared to the normal control group (RCAF: 497.62mm3 vs. NC: 158.58mm3, p = 0.001). High performance flight hours were significantly correlated with PVS volumes (r = 0.352, p = 0.022). Regression models revealed WMH were associated with Shipley-2 vocabulary scores (crystallized intelligence) standardized for age group (β=-0.307, p = 0.012), short-term visual memory (Delayed Matching-to-sample, Average Trial Accuracy, β=-.406, p = 0.001), and working memory updating (D-Prime for 1 back trials: hit rate - false alarm rate, β=-.320, p = 0.008). CONCLUSION: Canadian military aircrew in the RCAF have a higher burden of WMH compared to normal controls. The findings suggest that increases in WMH volumes, potentially due to extreme occupational and physiological stressors from long exposure to high performance flights, are associated with subtle neurocognitive impairment. Future analyses will examine the potential modulating effects related to changes in blood-based neurological injury biomarkers.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".