Whole‐Body Heat Loss is Enhanced in Older Adults Following a Summer in a Humid Continental Climate
Bibliographic record
Abstract
It has recently been shown that older adults have a reduced capacity to dissipate heat during exposure to extreme heat compared to their younger counterparts, resulting in a 1.7‐fold greater increase in body heat storage. However, it currently remains unclear whether older adults demonstrate any seasonal adaptations in their ability to dissipate over the course of a typical hot humid summer (e.g. Central Canada). Therefore, the purpose of this study was to examine the effects of aging on whole‐body heat loss and heat storage during an extreme heat exposure prior to (before June) and at the end of the summer (September). Five young (Young, age: 25 ± 3 years; body fat: 19 ± 6%) and five older (Older, age: 64 ± 7 years; body fat: 26 ± 9%) adults matched for body weight (Young: 82 ± 18 kg; Older: 86 ± 12 kg) and body surface area (Young: 1.9 ± 0.2 m 2 ; Older: 2.0 ± 0.2 m 2 ) rested for 3 hours in the heat (44°C, 30% RH). Whole‐body heat loss and metabolic heat production were measured continuously by direct and indirect calorimetry, respectively. Body heat storage was calculated as the temporal summation of heat production and heat loss. Our results show that the older adults had a reduced rate of whole‐body heat loss at the 1‐hour (Young: 105 ± 20 W vs. Older: 76 ± 12 W, p=0.021) and 2‐hour (Young: 115 ± 28 W vs. Older: 83 ± 11 W, p=0.048) time points prior to the start of summer relative to their younger counterparts. No differences were measured between age groups at the end of the 3‐hour heat exposure (p>0.05). As a result of the lower rate of heat loss, the older adults stored 1.3‐fold more heat than the young adults (170 ± 72 kJ, p=0.01). Following the summer period, no differences in the rate of whole‐body heat loss were measured between groups throughout the 3‐hour heat exposure. As a consequence, the change in body heat storage was similar between age groups (Young: 196 ± 113 kJ vs. Older: 226 ± 102 kJ, p=0.67), demonstrating that older adults were able to reduce the amount of heat stored within their body by 43% after 3 months of summer heat exposure in a humid continental climate. These results show that seasonal adaptations can improve whole‐body heat dissipation in older adults, thereby mitigating the age‐related impairments in the body's physiological capacity to dissipate heat during an extreme heat exposure. Support or Funding Information Funding support: This study was funded by the Canadian Institutes of Health Research (286363, grant held by Dr. Glen P. Kenny).
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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 | 0.000 |
| 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) | 0.001 | 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".