Premium
Whole‐Body Heat Loss is Enhanced in Older Adults Following a Summer in a Humid Continental Climate
Author(s) -
Poirier Martin P.,
Dervis Sheila,
Flouris Andreas D.,
Kenny Glen P.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1290.13
Subject(s) - medicine , thermal energy storage , young adult , body surface area , body weight , excess heat , calorimetry , zoology , gerontology , biology , thermodynamics , ecology , physics
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).