Physiological Strain In Older Adults During A Simulated Extreme Heat Event: A Case Study
Bibliographic record
Abstract
The likelihood of exposure to hot indoor environments is increasing as climate change exacerbates the frequency and severity of extreme heat events. Recent work from our laboratory demonstrated that older adults sustain greater increases in core temperature during a daylong (9-h) exposure to hot indoor conditions (40 °C) compared to their younger counterparts (PMID:37707866). While these findings represent an important step in quantifying the physiological effects of heat waves on heat-vulnerable individuals, there remains a need for extended studies performed over multiple days, as would occur in a natural heat event. PURPOSE: To evaluate the thermal and cardiovascular responses to a multi-day heatwave simulation in an older adult. METHODS: A 60-year-old male was housed in an environmental chamber for three successive days while exposed to a daytime temperature of 40 °C (45% relative humidity [RH]) for a 10-h period (9:00-19:00) and a nighttime temperature of 36 °C (45% RH) for a 14-h period (19:00-9:00). The participant was permitted to move freely throughout the day but not perform physical activity. A battery of tests assessing cardiovascular and cognitive function, and postural stability were performed in the final 2-h of daytime. Core temperature (rectal; Trec) and heart rate (HR) were measured prior to entry to the heat (ambient temperature; 22 °C) and continuously throughout the trial. RESULTS: Pre-trial resting Trec was 36.5 °C. Prior to the battery of tests (8-h into daytime exposure) Trec reached 37.5 °C, 37.8 °C and 37.5 °C and further increased by 0.2 °C, 0 °C and 0.3 °C at the end of daytime exposure (10-h) for days 1, 2 and 3 respectively. Nighttime was associated with a reduction in Trec, with end nighttime Trec decreasing to 36.9 °C (day 1), 37.0 °C (day 2) and 37.1 °C (day 3). Pre-trial HR was 46 beats per min (bpm), which increased to 66 bpm, 65 bpm, 59 bpm at 8-h, with a further increase of 7 bpm, 12 bpm and 9 bpm at end of daytime (10-h) and a decrease to 48 bpm, 48 bpm, 55 bpm at the end of nighttime for day 1 to 3 respectively. CONCLUSION: We showed that a multi-day exposure to extreme heat is associated with a sustained increase in physiological strain. Notably, the marked elevation in daytime Trec occurred despite a reduction in nighttime temperature closer to resting levels. Supported by: Health Canada HeatADAPT program
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".