TY - JOUR
T1 - Critical environmental core temperature limits and heart rate thresholds across the adult age span (PSU HEAT Project)
AU - Cottle, Rachel M.
AU - Fisher, Kat G.
AU - Leach, Olivia K.
AU - Wolf, S. Tony
AU - Kenney, W. Larry
N1 - Publisher Copyright:
© 2024 the American Physiological Society.
PY - 2024/7
Y1 - 2024/7
N2 - The frequency, duration, and severity of extreme heat events have increased and are projected to continue to increase throughout the next century. As a result, there is an increased risk of excessive heat- and cardiovascular-related morbidity and mortality during these extreme heat events. Therefore, the purposes of this investigation were to establish 1) critical environmental core temperature (Tc) limits for middle-aged adults (MA), 2) environmental thresholds that cause heart rate (HR) to progressively rise in MA and older (O) adults, and 3) examine critical environmental Tc limits and HR environmental thresholds across the adult age span. Thirty-three young (Y) (15 F; 23 ± 3 yr), 28 MA (17 F; 51 ± 6 yr), and 31 O (16 F; 70 ± 3 yr) subjects were exposed to progressive heat stress in an environmental chamber in a warm-humid (WH, 34–36°C, 50–90% rh) and a hot-dry (HD, 38°C–52°C, <30% rh) environment while exercising at a low metabolic rate reflecting activities of daily living (~1.8 METs). In both environments, there was a main effect of age on the critical environmental Tc limit and environmental HR thresholds (main effect of age all P < 0.001). Across the lifespan, critical environmental Tc and HR thresholds decline linearly with age in HD environments (R2 ≥ 0.3) and curvilinearly in WH environments (R2 ≥ 0.4). These data support an age-associated shift in critical environmental Tc limits and HR thresholds toward lower environmental conditions and can be used to develop evidence-based safety guidelines to minimize future heat-related morbidity and mortality across the adult age span.
AB - The frequency, duration, and severity of extreme heat events have increased and are projected to continue to increase throughout the next century. As a result, there is an increased risk of excessive heat- and cardiovascular-related morbidity and mortality during these extreme heat events. Therefore, the purposes of this investigation were to establish 1) critical environmental core temperature (Tc) limits for middle-aged adults (MA), 2) environmental thresholds that cause heart rate (HR) to progressively rise in MA and older (O) adults, and 3) examine critical environmental Tc limits and HR environmental thresholds across the adult age span. Thirty-three young (Y) (15 F; 23 ± 3 yr), 28 MA (17 F; 51 ± 6 yr), and 31 O (16 F; 70 ± 3 yr) subjects were exposed to progressive heat stress in an environmental chamber in a warm-humid (WH, 34–36°C, 50–90% rh) and a hot-dry (HD, 38°C–52°C, <30% rh) environment while exercising at a low metabolic rate reflecting activities of daily living (~1.8 METs). In both environments, there was a main effect of age on the critical environmental Tc limit and environmental HR thresholds (main effect of age all P < 0.001). Across the lifespan, critical environmental Tc and HR thresholds decline linearly with age in HD environments (R2 ≥ 0.3) and curvilinearly in WH environments (R2 ≥ 0.4). These data support an age-associated shift in critical environmental Tc limits and HR thresholds toward lower environmental conditions and can be used to develop evidence-based safety guidelines to minimize future heat-related morbidity and mortality across the adult age span.
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U2 - 10.1152/japplphysiol.00117.2024
DO - 10.1152/japplphysiol.00117.2024
M3 - Article
C2 - 38813613
AN - SCOPUS:85198679609
SN - 8750-7587
VL - 137
SP - 145
EP - 153
JO - Journal of applied physiology
JF - Journal of applied physiology
IS - 1
ER -