Influences of age and gender on human thermoregulatory responses to cold exposures

Wagner, J. A.; Horvath, Steven M.

doi:10.1152/jappl.1985.58.1.180

Cited by 114 publications

(78 citation statements)

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“…Previous studies have shown that T c may be maintained, decreased, or even slightly increased in response to cold stress (11,37,40). Young subjects tend to adequately defend T c during mild (11) but not more severe (37) cold stress.…”

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confidence: 92%

Responses to mild cold stress are predicted by different individual characteristics in young and older subjects

DeGroot¹,

Havenith²,

Kenney

2006

Journal of Applied Physiology

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ney. Responses to mild cold stress are predicted by different individual characteristics in young and older subjects. J Appl Physiol 101: 1607-1615, 2006. First published August 3, 2006 doi:10.1152/japplphysiol.00717.2006.-Older individuals' ability to maintain core temperature during cold stress is impaired; however, the relative importance of individual characteristics that influence this response are unknown. The purpose of this study was to determine the relative influence of individual characteristics on core temperature and tissue insulation (I t) during mild cold stress. Forty-two young (23 Ϯ 1 yr, range 18 -30 yr) and 46 older (71 Ϯ 1 yr, range 65-89 yr) subjects, varying widely in muscularity, adiposity, and body size, underwent a transient cooling protocol during which esophageal temperature (T es) was measured continuously and I t was calculated using standard equations. Multipleregression analyses were performed to determine predictors of T es and It, and standardized regression coefficients were analyzed to determine the relative influence of each predictor. Candidate predictors included age, sex, weight, body surface area, body surface area-to-mass ratio, sum of skinfolds, percent fat, appendicular skeletal muscle mass, and thyroid hormone concentrations (triiodothyronine, thyronine). The sum of skinfolds explained 67% (P Ͻ 0.01) of the T es variance in young subjects vs. 2% (P ϭ 0.30) in older subjects. Conversely, appendicular skeletal muscle mass explained a greater portion of the variance in older subjects for both T es (older: 28%, P Ͻ 0.01; young: 8%, not significant) and It (older: 46%, P Ͻ 0.01; young: 17%, P Ͻ 0.01). The Tes residual variance was considerably larger in older subjects (59 -72% vs. 14 -42% in young subjects), possibly due to varying rates of physiological aging. These results suggest that the relative influence of individual characteristics changes with aging. core temperature; tissue insulation; body composition; aging EPIDEMIOLOGICAL EVIDENCE SUGGESTS that older individuals are more susceptible to hypothermia than young individuals, with Ͼ50% of deaths due to hypothermia occurring in those aged Ͼ65 yr, an age cohort comprising only ϳ12% of the US population (8). Cross-sectional studies confirm that aged individuals have a relative inability to maintain core temperature

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confidence: 92%

Responses to mild cold stress are predicted by different individual characteristics in young and older subjects

DeGroot¹,

Havenith²,

Kenney

2006

Journal of Applied Physiology

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“…Venous occlusion plethysmography measurements of forearm blood flow are more dependent on muscle blood flow than skin blood flow during normothermic conditions (3). Therefore, it is unknown whether similar agerelated alterations in vasoconstriction occur in the cutaneous vasculature.Previous studies have observed increased convective heat loss and higher skin temperatures in the elderly during cold stress (15,18,31). This greater heat loss is not attributed to decreases in fitness but rather to the inability to reduce skin temperatures to the same degree in older compared with young subjects (1, 6).…”

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confidence: 95%

“…Previous studies have observed increased convective heat loss and higher skin temperatures in the elderly during cold stress (15,18,31). This greater heat loss is not attributed to decreases in fitness but rather to the inability to reduce skin temperatures to the same degree in older compared with young subjects (1, 6).…”

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confidence: 95%

Effect of age on cutaneous vasoconstrictor responses to norepinephrine in humans

Wilson

Monahan

Short

et al. 2004

American Journal of Physiology-Regulatory, Integrative and Comp

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. Effect of age on cutaneous vasoconstrictor responses to norepinephrine in humans. Am J Physiol Regul Integr Comp Physiol 287: R1230 -R1234, 2004 doi:10.1152/ajpregu.00467. 2004.-To test the hypothesis that cutaneous vasoconstrictor responsiveness to exogenous norepinephrine is reduced in older compared with young subjects, dose-response relations between norepinephrine and skin blood flow were established. Seven doses of norepinephrine (1 ⅐ 10 Ϫ8 to 10 Ϫ2 log M) were perfused (2 l/min) intradermally (4 min/dose) using cutaneous microdialysis (2 probes/subject). To account for possible differences in endogenous norepinephrine between groups, one microdialysis probe was perfused with bretylium tosylate to locally block noradrenergic vesicle release before establishing the norepinephrine dose-response relations. Skin blood flow was indexed via laser-Doppler flowmetry directly over both microdialysis probe sites and is expressed as cutaneous vascular conductance (laserDoppler flux/mean arterial blood pressure). Local skin temperature was maintained at 34°C at both sites throughout the protocol. Doseresponse relation between norepinephrine and cutaneous vascular conductance was similar between control and bretylium-pretreated sites in young subjects (EC 50 ϭ Ϫ5.18 Ϯ 0.27 and Ϫ5.03 Ϯ 0.27 log M, respectively). In contrast, the dose-response relation was significantly shifted to the right (i.e., a higher dose of norepinephrine was needed to produce the same vasoconstrictor response) in the bretylium-pretreated site in older subjects (EC 50 ϭ Ϫ5.46 Ϯ 0.23 and Ϫ4.53 Ϯ 0.23 log M, respectively). Significant increases in EC 50 were observed in older compared with young subjects at the bretylium-pretreated but not the control sites. These data indicate that cutaneous vasoconstrictor responsiveness is decreased in older subjects when endogenous release of norepinephrine is antagonized. Furthermore, these findings suggest that differences in presynaptic norepinephrine release between older and younger subjects are profound enough to affect dose-response relations between norepinephrine and cutaneous vascular conductance. intradermal microdialysis; ␣-adrenergic receptors; cold stress AGING modulates autonomic thermoregulatory responses during environmental stress (14,34,35). Reduced cutaneous vasodilation and sweating during heat stress are well established in older subjects (10,12,17,19,24). However, the effects of age on autonomic responses to cold stress are less clear. This lack of clarity is especially apparent when assessing age-related cutaneous vasoconstrictor responses.Kenney and Armstrong (13) have identified impaired rate and extent of forearm vasoconstriction in older subjects during a 120-min cold air stress. Although the mechanisms responsible for this vasoconstrictor deficit were not identified in this study, one possible mechanism for this impaired vasoconstrictor response in older adults could involve blunted end-organ responsiveness. Supporting this concept, Dinenno et al. (4) observed blunted vasoconstri...

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“…The cold environment response of the model was tested against a set of human subject experiments performed by Wagner and Horvath 14 . These experiments were performed on 10 men and 10 women between the ages of 20 and 30 and 10 men and 7 women between the ages of 51 and 72.…”

Section: Cold Casesmentioning

confidence: 99%

Dynamic Simulation of Human Thermoregulation and Heat Transfer for Spaceflight Applications

Miller

Nelson

Bue

et al. 2011

41st International Conference on Environmental Systems

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RetiredModels of human thermoregulation and heat transfer date from the early 1970s and have been developed for applications ranging from evaluating thermal comfort in spacecraft and aircraft cabin environments to predicting heat stress during EVAs. Most lumped or compartment models represent the body as an assemblage cylindrical and spherical elements which may be subdivided into layers to describe tissue heterogeneity. Many existing models are of limited usefulness in asymmetric thermal environments, such as may be encountered during an EVA. Conventional whole-body clothing models also limit the ability to describe local surface thermal and evaporation effects in sufficient detail. A further limitation is that models based on a standard man model are not readily scalable to represent large or small subjects.This work describes development of a new human thermal model derived from the 41-node man model. Each segment is divided into four concentric, constant thickness cylinders made up of a central core surrounded by muscle, fat, and skin, respectively. These cylinders are connected by the flow of blood from a central blood pool to each part. The central blood pool is updated at each time step, based on a whole-body energy balance.Results show the model simulates core and surface temperature histories, sweat evaporation and metabolic rates which generally are consistent with controlled exposures of human subjects. Scaling rules are developed to enable simulation of small and large subjects (5 th per centile and 95 th per centile). Future refinements will include a clothing model that addresses local surface insulation and permeation effects and developing control equations to describe thermoregulatory effects such as may occur with prolonged weightlessness or with aging.

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Influences of age and gender on human thermoregulatory responses to cold exposures

Cited by 114 publications

References 0 publications

Responses to mild cold stress are predicted by different individual characteristics in young and older subjects

Responses to mild cold stress are predicted by different individual characteristics in young and older subjects

Effect of age on cutaneous vasoconstrictor responses to norepinephrine in humans

Dynamic Simulation of Human Thermoregulation and Heat Transfer for Spaceflight Applications

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