Preferred room temperature of young vs aged males: the influence of thermal sensation, thermal comfort, and affect

Physiological responses to 9 hours of heat exposure in young and older adults. Part III: Association with self-reported symptoms and mood state

Older adults are at greater risk of heat-related morbidity and mortality during heat waves, which is commonly linked to impaired thermoregulation. However, little is known about the influence of increasing age on the relation between thermal strain and perceptual responses during daylong heat exposure. We evaluated thermal and perceptual responses in 20 young (19-31 yr) and 39 older adults (20 with hypertension and/or type 2 diabetes; 61-78 yr) resting in the heat for 9 h (heat index: 37°C). Body core and mean skin temperature areas under the curve (AUC, hours 0-9) were assessed as indicators of cumulative thermal strain. Self-reported symptoms (68-item environmental symptoms questionnaire) and mood disturbance (40-item profile of mood states questionnaire) were assessed at end-heating (adjusted for prescores). Body core temperature AUC was 2.4°C·h [1.0, 3.7] higher in older relative to young adults (P < 0.001), whereas mean skin temperature AUC was not different (-0.5°C·h [-4.1, 3.2] P = 0.799). At end-heating, self-reported symptoms were not different between age groups (0.99-fold [0.80, 1.23], P = 0.923), with or without adjustment for body core or mean skin temperature AUC (both P ≥ 0.824). Mood disturbance was 0.93-fold [0.88, 0.99] lower in older, relative to young adults (P = 0.031). Older adults with and without chronic health conditions experienced similar thermal strain, yet those with these conditions reported lower symptom scores and mood disturbance compared with young adults and their age-matched counterparts (all P ≤ 0.026). Although older adults experienced heightened thermal strain during the 9-h heat exposure, they did not experience greater self-reported symptoms or mood disturbance relative to young adults.NEW & NOTEWORTHY Despite experiencing greater cumulative thermal strain during 9 h of passive heat exposure, older adults reported similar heat-related symptoms and lower mood disturbance than young adults. Furthermore, self-reported symptoms and mood disturbance were lower in older adults with common age-associated health conditions than young adults and healthy age-matched counterparts. Perceptual responses to heat in older adults can underestimate their level of thermal strain compared with young adults, which may contribute to their increased heat vulnerability.

Indoor overheating influences self-reported symptoms and mood-state in older adults during a simulated heatwave: Effects of mid-day cooling centre use

Public health agencies recommend that older adults without home air-conditioning visit cooling centres to mitigate physiological strain from high ambient temperatures during heat waves. However, there is little evidence regarding their influence on self-reported environmental symptoms and mood-state after returning to the heat.

METHODS

Forty adults (64-79 years) underwent a daylong laboratory-based indoor overheating simulation (9-hours, heat index: 37 °C) with (cooling, n = 20) or without (control, n = 20) a 2-hour air-conditioning intervention (hours 5-6). Mean skin and core temperature areas under the curve (AUC, hours 0-9) were used to assess cumulative thermal strain. Group differences in total symptom scores and subjective heat illness (68-item environmental symptoms questionnaire) as well as total mood disturbance and energy index (40-item profile of mood states questionnaire) were evaluated at end-heating (adjusted for pre-exposure scores).

RESULTS

Cooling reduced mean skin and core temperature AUCs by 4.0 [0.1, 0.8] and 1.6 [0.4, 2.8] °C·hour compared to control (both p < 0.048). However, at end-heating neither mean skin nor core temperatures differed between groups (both p > 0.999). Total symptom scores and subjective heat illness were 0.58-fold [0.44, 0.77] and 0.56-fold [0.40, 0.78] lower in the cooling compared to control group (both p < 0.001). Mood disturbance was 0.91-fold [0.83, 0.99] lower for cooling than control (p = 0.036), although energy index was not different between groups (p = 0.141).

CONCLUSION

Cooling centres can have sustained positive effects on perceived thermal strain and mood-state in older adults after returning to the heat. However, continued vigilance and use of appropriate countermeasures to mitigate physiological strain from indoor overheating should be encouraged as body temperatures can rapidly return to pre-cooling levels.

A review of Japanese-style bathing: its demerits and merits

Japanese-style bathing (JSB), which involves soaking in hot water up to the shoulders in deep bathtubs for a long time in the evening to night, is unique. Many experimental and epidemiological studies and surveys have shown that JSB improve sleep quality, especially shortens sleep onset latency in winter. In addition, repeated JSB lead the improvement of depressive symptoms. JSB is a simple and low-cost non-pharmacological measure to sleep difficulty in winter and mental disorders, especially for the elderly. On the contrary, drowning, while soaking in a bathtub, is the most common of accidental death at home in Japan. It is estimated that approximately 19,000 Japanese individuals die annually while taking a bath, mostly during winter, and most victims are elderly people. Elderly Japanese people tend to prefer a higher-risk JSB because the temperature inside the house during winter, especially the dressing room/bathroom temperature, is very low. Since the physiological thermal effect of the elderly associated with bathing is relatively lower among the elderly than the young, the elderly prefer to take a long hot bath. This elderly’s favorite style of JSB results in larger increased blood pressure in dressing rooms and larger decreased in blood pressure during hot bathing. A sudden drop in blood pressure while immersed in the bathtub leads to fainting and drowning. Furthermore, elderly people are less sensitive to cold air or hot water, therefore, it is difficult to take appropriate measures to prevent large fluctuations in blood pressure. To ensure a safe and comfortable winter bathing, the dressing room/bathroom temperature needs to be maintained at 20 °C or higher, and several degrees higher would be recommended for the elderly.

Effects of body geometry, body composition, cardio-pulmonary capacity, and fitness on young men's thermal preference

This paper investigated principal parameters affecting individual differences of thermal preference. 36 male college students were selected from three thermal preference groups by a questionnaire, including 10 of cool preference (Gcp), 17 of neutral preference (Gnp), and 9 of warm preference (Gwp). Subsequently, their thermal preferences were further examined by a human trial in a climate chamber. Once significant differences were found between groups, subjects' 57 parameters, including body geometry, body composition, cardio-pulmonary capacity, and physical fitness, were measured. Compared to Gwp, Gcp had higher weight (80.0 vs. 64.2 kg), body mass index (BMI) (26 vs. 20.8 kg·m^-2 ), body surface area (BSA) (1.94 vs. 1.78 m² ), waist-to-hip ratio (WHR) (87.29% vs. 80.23%), body circumferences (except for forearm circumference), skinfold thickness of all the local parts, volume of expired air (VE) (50.97 vs. 40.81 L/min), and body fat rate (BFR) (24.44% vs. 14.07%), but had a lower specific surface area (SSA) (0.02477 vs. 0.02791 m² /kg), resting metabolic rate (RMR) per kilogram (1.21 vs. 1.47 W/kg), diastolic blood pressure (DBP) (65.30 vs. 74.69 mmHg), and percentages of muscle (71.17% vs. 80.95%), total water (55.35% vs. 63.14%), skeletal muscle (42.47% vs. 47.94%), protein (14.90% vs. 16.94%), inorganic salt (5.29% vs. 5.86%), and bone mineral (0.044% vs. 0.048%). Among these parameters, body fat and SSA played a dominant role (accounting for 85.76%) in explaining individual differences in thermal preference.

Perception of Thermal Comfort during Skin Cooling and Heating

Due to the static and dynamic activity of the skin temperature sensors, the cutaneous thermal afferent information is dependent on the rate and direction of the temperature change, which would suggest different perceptions of temperature and of thermal comfort during skin heating and cooling. This hypothesis was tested in the present study. Subjects (N = 12; 6 females and 6 males) donned a water-perfused suit (WPS) in which the temperature was varied in a saw-tooth manner in the range from 27 to 42 °C. The rate of change of temperature of the water perfusing the suit (T_WPS) was 1.2 °C min^-1 during both the heating and cooling phases. The trial was repeated thrice, with subjects reporting their perception of the temperature and thermal comfort at each 3 °C change in T_WPS. In addition, subjects were instructed to report when they perceived T_WPS uncomfortably cool and warm during cooling and heating, respectively. Subjects reproducibly identified the boundaries of their Thermal Comfort Zone (TCZ), defined as the lower (T_low) and upper (T_high) temperatures at which subjects reported slight thermal discomfort. During the heating phase, T_low and T_high were 30.0 ± 1.5 °C and 35.1 ± 2.9 °C, respectively. During the cooling phase, the boundary temperatures of T_low and T_high were 35.4 ± 1.9 °C and 38.7 ± 2.3 °C, respectively. The direction of the change in the cutaneous temperature stimulus affects the boundaries of the TCZ, such that they are higher during cooling and lower during heating. These findings are explained on the basis of the neurophysiology of thermal perception. From an applied perspective, the most important observation of the present study was the strong correlation between the perception of thermal comfort and the behavioral regulation of thermal comfort. Although it is not surprising that the action of regulating thermal comfort is aligned with its perception, this link has not been proven for humans in previous studies. The results therefore provide a sound basis to consider ratings of thermal comfort as reflecting behavioral actions to achieve the sensation of thermal neutrality.

Thermoregulatory reflex control of cutaneous vasodilation in healthy aging

Reflex cutaneous vasodilation during heating is attenuated in healthy human aging secondary to blunted increases in efferent skin sympathetic nervous system activity (SSNA) and reductions in end-organ sensitivity. Whether age-related alterations in the mean body temperature ( T - _b) threshold for increasing SSNA and/or the sensitivity of responses are evident with aging have not been examined. We tested the hypotheses that the T_b threshold for SSNA and cutaneous vascular conductance (CVC) would be increased, but the sensitivity would be reduced, with aging. Reflex vasodilation was induced in 13 young (23 ± 3 y) and 13 older (67 ± 7 y) adults using a water-perfused suit to systematically increase mean skin and esophageal temperatures. SSNA (peroneal microneurography) and red cell flux (laser Doppler flowmetry) in the innervated dermatome were continuously measured. SSNA was normalized to baseline; CVC was normalized as a percentage of maximal CVC. Baseline T - _b was lower in older adults (36.0 ± 0.4°C vs 36.4 ± 0.3°C; p = 0.005). During passive heating, the ∆ T - _b thresholds for increasing SSNA and CVC were greater (1.3 ± 0.4°C vs 0.9 ± 0.3°C; p = 0.007 and 1.3 ± 0.4°C vs 0.8 ± 0.3°C; p = 0.002, respectively) in older adults. The slope of the relation between both SSNA (0.31 ± 0.23 vs 0.13 ± 0.10 V⋅s⋅°C ^-1; p = 0.01) and CVC (87.5 ± 50.1 vs 32.4 ± 18.1%max⋅°C^-1; p = 0.002) vs T - _b was lower in older adults. The relative T - _b threshold for activation of SSNA and the initiation of reflex cutaneous vasodilation is higher in older adults, and once activated, the sensitivity of both responses is diminished, supporting the concept that the efferent component of the thermoregulatory reflex arc is impaired in healthy aging. Abbreviations: CI: confidence interval; CVC: cutaneous vascular conductance; SSNA: skin sympathetic nervous system activity; T - _b: mean body temperature; T_es: esophageal temperature; T - _sk: mean skin temperature.

Kidney physiology and pathophysiology during heat stress and the modification by exercise, dehydration, heat acclimation and aging

The kidneys' integrative responses to heat stress aid thermoregulation, cardiovascular control, and water and electrolyte regulation. Recent evidence suggests the kidneys are at increased risk of pathological events during heat stress, namely acute kidney injury (AKI), and that this risk is compounded by dehydration and exercise. This heat stress related AKI is believed to contribute to the epidemic of chronic kidney disease (CKD) occurring in occupational settings. It is estimated that AKI and CKD affect upwards of 45 million individuals in the global workforce. Water and electrolyte disturbances and AKI, both of which are representative of kidney-related pathology, are the two leading causes of hospitalizations during heat waves in older adults. Structural and physiological alterations in aging kidneys likely contribute to this increased risk. With this background, this comprehensive narrative review will provide the first aggregation of research into the integrative physiological response of the kidneys to heat stress. While the focus of this review is on the human kidneys, we will utilize both human and animal data to describe these responses to passive and exercise heat stress, and how they are altered with heat acclimation. Additionally, we will discuss recent studies that indicate an increased risk of AKI due to exercise in the heat. Lastly, we will introduce the emerging public health crisis of older adults during extreme heat events and how the aging kidneys may be more susceptible to injury during heat stress.

Body mapping of regional sweat distribution in young and older males

Purpose

Given the pressing impact of global warming and its detrimental effect on the health of older populations, understanding age-related changes in thermoregulatory function is essential. Age differences in regional sweat distribution have been observed previously, but given the typically small measurement areas assessed, the development of whole body sweat maps for older individuals is required. Therefore, this study investigated age-related differences in regional sweat distribution in a hot environment (32 °C/50%RH) in young and older adults, using a body mapping approach.

Methods

Technical absorbent pads were applied to the skin of 14 young (age 24 ± 2 years) and 14 older (68 ± 5 years) males to measure regional sweat rate (RSR) at rest (30 min) and during exercise (30 min), at a fixed heat production (200 W m⁻²). Gastrointestinal (T_gi) and skin temperature (T_sk), heart rate, thermal sensation, and thermal comfort were also measured.

Results

Whole body sweat maps showed that despite equal heat production, healthy older males had significantly lower gross sweat loss (GSL) than the young and significantly lower RSR at almost all body regions at rest and at the hands, legs, ankles, and feet during exercise. The lower sweat loss in the older group coincided with a greater increase in T_gi and a consistently higher T_sk at the legs, despite subjectively feeling slightly cooler than younger individuals.

Conclusion

These findings support the evidence of age-related deterioration in both autonomic and subjective responses in the heat and highlight the lower extremities as the most affected body region.

Electronic supplementary material

The online version of this article (10.1007/s00421-020-04503-5) contains supplementary material, which is available to authorized users.

Thermal Sensation in Older People with and without Dementia Living in Residential Care: New Assessment Approaches to Thermal Comfort Using Infrared Thermography

The temperature of the indoor environment is important for health and wellbeing, especially at the extremes of age. The study aim was to understand the relationship between self-reported thermal sensation and extremity skin temperature in care home residents with and without dementia. The Abbreviated Mental Test (AMT) was used to discriminate residents to two categories, those with, and those without, dementia. After residents settled and further explanation of the study given (approximately 15 min), measurements included: tympanic membrane temperature, thermal sensation rating and infrared thermal mapping of non-dominant hand and forearm. Sixty-nine afebrile adults (60-101 years of age) were studied in groups of two to five, in mean ambient temperatures of 21.4-26.6 °C (median 23.6 °C). Significant differences were observed between groups; thermal sensation rating (p = 0.02), tympanic temperature (p = 0.01), fingertip skin temperature (p = 0.01) and temperature gradients; fingertip-wrist p = 0.001 and fingertip-distal forearm, p = 0.001. Residents with dementia were in significantly lower air temperatures (p = 0.001). Although equal numbers of residents per group rated the environment as 'neutral' (comfortable), resident ratings for 'cool/cold' were more frequent amongst those with dementia compared with no dementia. In parallel, extremity (hand) thermograms revealed visual temperature demarcation, variously across fingertip, wrist, and forearm commensurate with peripheral vasoconstriction. Infrared thermography provided a quantitative and qualitative method to measure and observe hand skin temperature across multiple regions of interest alongside thermal sensation self-report. As an imaging modality, infrared thermography has potential as an additional assessment technology with clinical utility to identify vulnerable residents who may be unable to communicate verbally, or reliably, their satisfaction with indoor environmental conditions.

Autonomic and perceptual thermoregulatory responses to voluntarily engaging in a common thermoregulatory behaviour

We examined whether partial clothing removal is an effective thermoregulatory behaviour to attenuate both thermoregulatory and perceptual strain in a moderate environment (23 °C, 65% RH) during and after exercise. Ten healthy males (age: 21.9 (0.9) years; height: 173.9 (6.2) cm; mass: 62.3 (8.2) kg; body surface area: 1.8 (0.1) m²; VO₂max: 51.8 (13.3) mL.kg^-1.min^-1) wore a long sleeve polyester shirt and performed two randomized cycling trials for 40 min at 40% VO₂max followed by 20 min recovery. In one trial, they were permitted to roll up their sleeves at any time they wanted (Roll) whereas in the other trial, they were instructed to remain with long sleeves (No Roll) until the end of the recovery. Thermoregulatory variables were measured continuously whilst thermal perceptions (forearm wettedness perception (WP_Forearm), forearm and whole-body thermal discomfort (TD_Forearm, TD_Whole), local and whole-body thermal sensation (TS_Forearm, TS_Whole) and whole-body wettedness perception (WP_whole)) were measured every 10 min. All subjects behaved by rolling up their sleeves at 21.6 (4.7) minutes. T_skin (32.3 (0.2) °C, vs 32.0 (0.1) °C, p = 0.03), local sweat rate on the forearm (0.24 (0.08) mg.cm^-2.min^-1 vs 0.2 (0.04) mg.cm^-2.min^-1, p = 0.05), WP_Forearm, TD_Forearm, TS_Forearm and WP_Whole were all lower in Roll than No Roll (all p < 0.05) whilst T_core and cutaneous vascular conductance (CVC) on the forearm were not different (all p > 0.7) throughout the entire trial. We conclude that this behavioural response is an effective thermoregulatory behaviour to modulate local sudomotor function and thermal perceptions, WP_Whole during exercise but only T_sk, TD_Forearm WP_Forearm and WP_Whole persisted throughout the recovery in a moderate environment.

Study on Environment Regulation of Residential in Severe Cold Area of China in Winter: Base on Outdoor Thermal Comfort of the Elderly

Overwhelming evidence shows that the harsh climate conditions are affecting urban residents who are living in severe cold areas of China in winter, particularly affecting the frequency and length of outdoor space usage of the elderly. This study aims (1) to establish the modified model which is suitable for the harsh climate region, (2) to verify whether the physiological equivalent temperature (PET) index can be evaluated for the outdoor thermal comfort of older adults in severe cold areas of China in winter, (3) to draw the thermal comfort map that is based on the former conclusions. In this study, the outdoor environments in typical residential areas for the elderly of Changchun, China, has been investigated by using field measurement, questionnaire survey, and Computational Fluid Dynamics (CFD) simulation. The results show that the wind direction is the important aspects of model modification and quite possibly one of the most neglected. In addition, it is convenient to evaluate outdoor thermal comfort of the elderly on the basis of the PET index and the neutral PET temperature of elderly people who live in severe cold areas of China in winter is −0.5 degrees Celsius. According to the thermal comfort map, the park green land of urban residential is the best area for the elderly.

Reference Values for the Adolescent/Adult Sensory Profile in Spain

IMPORTANCE

In Spain, only one culturally adapted assessment tool is available for children between ages 3 and 11 yr. There are no assessments of adolescent and adult sensory processing, and no normative data.

OBJECTIVE

To obtain reference values for the Adolescent/Adult Sensory Profile (AASP) in Spain for adolescents (aged 11-17) and adults (aged 18-64 and ≥65).

DESIGN

A multivariate analysis of variance was used to compare specific mean values (-2, -1, +1, and +2 standard deviation [SD]) by age group, gender, geographic area, education level, and employment status.

PARTICIPANTS

We randomly recruited 787 participants (55.8% female) aged 11 yr or older (mean age = 32.1, SD = 21.1) in Spain. We excluded those with a diagnosis of depression, chronic disease (e.g., diabetes, cancer, neurological disease), or cognitive disability and those who used medication that could affect the central nervous system.

RESULTS

Quadrant mean (SD) scores ranged from 29.3 (6.6) for low registration to 49.1 (8.3) for sensory seeking, with significant differences by age group (p < .001) in all quadrants. Significant differences were also found for scores in different quadrants by gender, geographic area, education level, and employment status. Although statistically significant, the differences between scores were not clinically relevant; the mean scores fell within the typical range for sensory processing.

CONCLUSIONS AND RELEVANCE

We offer reference values for the cultural adaptation to Spain of the AASP and recommend its use for the typically developing Spanish population ages 11 and older.

WHAT THIS ARTICLE ADDS

We provide normative data for the AASP for three age groups of the Spanish population: adolescents, adults, and older adults.

A Building Information Model (BIM) and Artificial Neural Network (ANN) Based System for Personal Thermal Comfort Evaluation and Energy Efficient Design of Interior Space

It is crucial to evaluate indoor personal thermal comfort for a comfortable and green thermal environment. At present, the research on individual thermal comfort does not consider its implementation mode. Moreover, the improvement of energy saving efficiency under the premise of increasing human comfort is an urgent problem that needs to be solved. In this paper, we proposed a Building Information Model (BIM) and Artificial Neural Network (ANN) based system to solve this problem. The system consists of two parts including an ANN predictive model considering the Predicted Mean Vote (PMV) index, the persons’ position, and an innovative plugin of BIM to realize dynamic evaluation and energy efficient design. The ANN model has three layers, considering three environment parameters (air temperature, air humidity, and wind speed around the person), three human state parameters (human metabolism rate, clothing thermal resistance, and the body position) and four body parameters (gender, age, height, and weight) as inputs. The plugin provides two functions. One is to provide corresponding personal thermal comfort evaluation results with dynamic changes of parameters returned by Wireless Sensor Networks (WSN). The other one is to provide energy saving optimization suggestions for interior space design by simulating the energy consumption index of different design schemes. In the data test, the Mean Squared Error (MSE) of the established ANN model was about 0.39, while the MSE of traditional PMV model was about 2.1. The system realized the integration of thermal information and a building model, thereby providing guidance for the creation of a comfortable and green indoor environment.

[Thermal comfort for the elderly: A systematic review of the scientific literature]

By 2050, people over 65 years old will represent 66% of the world's population. Thermal comfort both indoors and outdoors is one of the most influential factors to improve their quality of life in cities. The aim of this paper is to present a systematic review of the literature that identifies differences in thermal comfort temperature between older adults and other age groups, as well as to determine the factors that influence them. The review focused on studies published between 2000 and 2018. The results show that, for physiological, psychological, and physical reasons, there were differences between 0.2 and 4°C. However, the published studies were heterogeneous in terms of methodologies and sample size. Likewise, few determine the comfort temperature range for older people in a given climate, demonstrating the opportunity for future lines of research.

The effect of hot and cold drinks on thermoregulation, perception, and performance: the role of the gut in thermoreception

PURPOSE

Hot compared to cold drinks alter sweating responses during very low intensity exercise in temperate conditions. The thermoregulatory, perceptual, and performance effects of hot compared to cold drinks in hot, dry conditions during high-intensity exercise have not been examined.

METHOD

Ten participants [mean ± SD characteristics age 25 ± 5 years, height 1.81 ± 0.07 m, body mass 73.5 ± 10.6 kg, maximal power output (P_Max) 350 ± 41 W] completed two conditions, where they drank four boluses (ingested at - 9, 15, 30, and 45 min, respectively) of 3.2 mL kg^- 1 (~ 960 mL total) of either a COLD (5.3 °C) or a HOT drink (49.0 °C), which were contrasted to a no-drink CONTROL. They cycled for 60-min [55% P_Max in hot (34.4 °C) dry (34% RH)] ambient conditions followed by a test to exhaustion (TTE; 80% P_Max). The thermoregulatory, performance, and perceptual implications of drink temperature were measured.

RESULTS

TTE was worse in the CONTROL (170 ± 132 s) than the COLD drink (371 ± 272 s; p = 0.021) and HOT drink conditions (367 ± 301 s; p = 0.038) which were not different (p = 0.965). Sweat responses [i.e., reflex changes in mean skin temperature (T_msk) and galvanic skin conductance] indicated transient reductions in sweating response after COLD drink ingestion. The COLD drink improved thermal comfort beyond the transient changes in sweating.

CONCLUSION

Only COLD drink ingestion changed thermoregulation, but improved perceptual response. Accordingly, we conclude a role for gut thermoreception in thermal perception during exercise in hot, dry conditions.

In Shackleton's trails: Central and local thermoadaptive modifications to cold and hypoxia after a man-hauling expedition on the Antarctic Plateau

Cold and hypoxia constitute the main environmental stressors encountered on the Antarctic Plateau. Hence, we examined whether central and/or peripheral acclimatisation to the combined stressors of cold and hypoxia would be developed in four men following an 11-day man-hauling expedition on this polar region. Before and after the journey, participants performed a static whole-body immersion in 21 °C water, during which they were breathing a hypoxic gas (partial pressure of inspired O₂: ~97 mmHg). To evaluate their local responses to cold, participants also immersed the hand into 8 °C water for 30 min, while they were whole-body immersed and mildly hypothermic [i.e. 0.5 °C fall in rectal temperature (T_rec) from individual pre-immersion values]. T_rec and skin temperature (T_sk), skin blood flux, and oxygen uptake (reflecting shivering thermogenesis) were monitored throughout. The polar expedition accelerated by ~14 min the drop in T_rec [final mean (95% confidence interval) changes in T_rec: Before = -0.94 (0.15) °C, After: - 1.17 (0.23) °C]. The shivering onset threshold [Before: 19 (22) min, After: 25 (19) min] and gain [Before: - 4.19 (3.95) mL min^-1 kg^-1, After: - 1.70 (1.21) mL min^-1 kg^-1] were suppressed by the expedition. T_sk did not differ between trials. The development of a greater post-expedition hypothermic state did not compromise finger circulation during the hand-cooling phase. Present findings indicate therefore that a hypothermic pattern of cold acclimatisation, as investigated in hypoxia, was developed following a short-term expedition on the South Polar Plateau; an adaptive response that is characterised mainly by suppressed shivering thermogenesis, and partly by blunted cutaneous vasoconstriction.

The Role of Capillaries in the Lesser Ailments of Old Age and in Alzheimer's Disease and Vascular Dementia: The Potential of Pro-Therapeutic Angiogenesis

Apart from chronic diseases (arthritis, diabetes, etc.), old age is generally characterized by three lesser ailments: muscle weakness, minor memory lapses, and cold intolerance. This trio of complaints may have a common, underlying cause, namely, the age-associated reduced microcirculation in muscles, brain, skin, and elsewhere in the body. The Angiogenesis Hypothesis proposes that old age is in part a deficiency disease due to the decline in angiogenic (AG) factors, resulting in a reduced capillary density (CD) throughout the body. Over fifty published papers document waning levels of AG factors and/or decreased CD in various organ systems of aged animals and people, including those with Alzheimer's disease. The deficiency of AG factors is analogous to that of certain hormones (e.g., testosterone) whose blood levels also decline with age. In theory, therapeutic angiogenesis employing recombinant AG factors is a tenable treatment for the lesser ailments of old age and may improve the later years of human life. An optimal administration route may be intranasal.

Behavioral thermoregulation in older adults with cardiovascular co-morbidities

We tested the hypotheses that older adults with cardiovascular co-morbidities will demonstrate greater changes in body temperature and exaggerated changes in blood pressure before initiating thermal behavior. We studied twelve healthy younger adults (Younger, 25 ± 4 y) and six older adults ('At Risk', 67 ± 4 y) taking prescription medications for at least two of the following conditions: hypertension, type II diabetes, hypercholesterolemia. Subjects underwent a 90-min test in which they voluntarily moved between cool (18.1 ± 1.8°C, RH: 29 ± 5%) and warm (40.2 ± 0.3°C, RH: 20 ± 0%) rooms when they felt 'too cool' (C→W) or 'too warm' (W→C). Mean skin and intestinal temperatures and blood pressure were measured. Data were analyzed as a change from pretest baseline. Changes in mean skin temperature were not different between groups at C→W (Younger: +0.2 ± 0.8°C, 'At Risk': +0.7 ± 1.8°C, P = 0.51) or W→C (Younger: +2.7 ± 0.6°C, 'At Risk': +2.9 ± 1.9°C, P = 0.53). Changes in intestinal temperature were not different at C→W (Younger: 0.0 ± 0.1°C, 'At Risk': +0.1 ± 0.2, P = 0.11), but differed at W→C (-0.1 ± 0.2°C vs. +0.1 ± 0.3°C, P = 0.02). Systolic pressure at C→W increased (Younger: +10 ± 9 mmHg, 'At Risk': +24 ± 17 mmHg) and at W→C decreased (Younger: -4 ± 13 mmHg, 'At Risk': -23 ± 19 mmHg) to a greater extent in 'At Risk' (P ≤ 0.05). Differences were also apparent for diastolic pressure at C→W (Younger: -2 ± 4 mmHg, 'At Risk': +17 ± 23 mmHg, P < 0.01), but not at W→C (Younger Y: +4 ± 13 mmHg, 'At Risk': -1 ± 6 mmHg, P = 0.29). Despite little evidence for differential control of thermal behavior, the initiation of behavior in 'at risk' older adults is preceded by exaggerated blood pressure responses.

Activation of autonomic thermoeffectors preceding the decision to behaviourally thermoregulate in resting humans

What is the central question of this study? Do increases in metabolic heat production and sweat rate precede the initiation of thermoregulatory behaviour in resting humans exposed to cool and warm environments? What is the main finding and its importance? Thermoregulatory behaviour at rest in cool and warm environments is preceded by changes in vasomotor tone in glabrous and non-glabrous skin, but not by acute increases in metabolic heat production or sweat rate. These findings suggest that sweating and shivering are not obligatory for thermal behaviour to be initiated in humans. We tested the hypothesis that acute increases in metabolic heat production and sweating precede the initiation of thermoregulatory behaviour in resting humans exposed to cool and warm environments. Twelve healthy young subjects passively moved between 17 and 40°C rooms when they felt 'too cool' (C→W) or 'too warm' (W→C). Skin and internal (intestinal) temperatures, metabolic heat production, local sweat rate (forearm and chest) and cutaneous vascular conductance (CVC; forearm and fingertip) were measured continually. Compared with pretest baseline (31.8 ± 0.3°C), skin temperature was higher at C→W (32.0 ± 0.7°C; P = 0.01) and W→C (34.5 ± 0.5°C; P < 0.01). Internal temperature did not differ (P = 0.12) between baseline (37.2 ± 0.3°C), C→W (37.2 ± 0.3°C) and W→C (37.0 ± 0.3°C). Metabolic heat production was not different from baseline (40 ± 9 W m^-2 ) at C→W (39 ± 7 W m^-2 ; P = 0.50). Forearm (0.06 ± 0.01 mg cm^-2  min^-1 ) and chest (0.04 ± 0.02 mg cm^-2  min^-1 ) sweat rate at W→C did not differ from baseline (forearm, 0.05 ± 0.02 mg cm^-2  min^-1 and chest, 0.04 ± 0.02 mg cm^-2  min^-1 ; P ≥ 0.23). Forearm CVC was not different from baseline (0.30 ± 0.21 perfusion units (PU) mmHg^-1 ) at C→W (0.24 ± 0.11 PU mmHg^-1 ; P = 0.17), but was higher at W→C (0.65 ± 0.33 PU mmHg^-1 ; P < 0.01). Fingertip CVC was different from baseline (2.6 ± 2.0 PU mmHg^-1 ) at C→W (0.70 ± 0.42 PU mmHg^-1 ; P < 0.01) and W→C (4.49 ± 1.66 PU mmHg^-1 ; P < 0.01). Thermoregulatory behaviour at rest in cool and warm environments is preceded by changes in vasomotor tone in glabrous and non-glabrous skin, but not by acute increases in metabolic heat production or sweat rate.

The Role of Sensory Processing in the Everyday Lives of Older Adults

This study investigated whether there are age-related differences in sensory processing within daily life. Participants included 404 community-dwelling adults divided into three age groups: 19 to 34 years old (127 individuals), 35 to 64 years old (126 individuals), and 65 years and older (151 individuals). Each participant completed the Adolescent/Adult Sensory Profile. There was a difference in sensory processing between the three groups (p = .000), with the older adults noticing sensory input less than the young and middle aged adults (p = .002 for both groups). Both middle aged and older adults engaged in less sensory seeking behaviors than did young adults (p = .012 and p = .000, respectively). In an additional analysis, the older group was subdivided into four age groups (65 to 69 years, 70 to 74 years, 75 to 79 years, and 80 years and older). There was an age-related difference between the four groups (p = .000). Those 75 to 79 years old and those 80 years and older noticed sensory input less than did those younger than 70 years (p = .002 and p = .001, respectively). Those 80 years and older were also less apt to seek sensory experiences than were those younger than 70 years (p = .011). The authors propose hypotheses about the meaning of these findings and provide recommendations for the application of this knowledge to support older adults to age in place successfully.

Lower thermal sensation in normothermic and mildly hyperthermic older adults

PURPOSE

It is important to know how thermal sensation is affected by normal aging under conditions that elevate core body temperature for the prevention of heat-related illness in older people. We assessed whether thermal sensation under conditions of normothermia (NT) and mild hyperthermia (HT) is lowered in older adults.

METHODS

Seventeen younger (23 ±  3 years) and 12 older (71 ±  3 years) healthy men underwent measurements of the cold and warmth detection thresholds ( ± 0.1 °C/s) of their chest and forearm skin, and whole body warmth perception under NT (esophageal temperature, T es, ~36.5 °C) and HT (T es, ~37.3 °C; lower legs immersed in 42 °C water) conditions.

RESULTS

Warmth detection threshold at the forearm was increased in older compared with younger participants under both NT (P = 0.006) and HT (P = 0.004) conditions. In contrast, cold detection threshold at the forearm was decreased in older compared with younger participants under NT (P = 0.001) but not HT (P = 0.16). Mild hyperthermia decreased cold detection threshold at forearm in younger participants (P = 0.001) only. There were no effects of age and condition on warmth and cold detection thresholds at chest. Whole body warmth perception increased during HT compared with NT in both groups (both, P < 0.001), and older participants had lower values than the younger group under NT (P = 0.001) and HT (P = 0.051).

CONCLUSIONS

Skin warmth detection thresholds at forearm and whole body warmth perception under NT and HT and skin cold detection thresholds at forearm under NT deteriorated with aging.

Human whole body cold adaptation

Reviews on whole body human cold adaptation generally do not distinguish between population studies and dedicated acclimation studies, leading to confusing results. Population studies show that indigenous black Africans have reduced shivering thermogenesis in the cold and poor cold induced vasodilation in fingers and toes compared to Caucasians and Inuit. About 40,000 y after humans left Africa, natives in cold terrestrial areas seems to have developed not only behavioral adaptations, but also physiological adaptations to cold. Dedicated studies show that repeated whole body exposure of individual volunteers, mainly Caucasians, to severe cold results in reduced cold sensation but no major physiological changes. Repeated cold water immersion seems to slightly reduce metabolic heat production, while repeated exposure to milder cold conditions shows some increase in metabolic heat production, in particular non-shivering thermogenesis. In conclusion, human cold adaptation in the form of increased metabolism and insulation seems to have occurred during recent evolution in populations, but cannot be developed during a lifetime in cold conditions as encountered in temperate and arctic regions. Therefore, we mainly depend on our behavioral skills to live in and survive the cold.

Body temperature regulation in diabetes

The effects of type 1 and type 2 diabetes on the body's physiological response to thermal stress is a relatively new topic in research. Diabetes tends to place individuals at greater risk for heat-related illness during heat waves and physical activity due to an impaired capacity to dissipate heat. Specifically, individuals with diabetes have been reported to have lower skin blood flow and sweating responses during heat exposure and this can have important consequences on cardiovascular regulation and glycemic control. Those who are particularly vulnerable include individuals with poor glycemic control and who are affected by diabetes-related complications. On the other hand, good glycemic control and maintenance of aerobic fitness can often delay the diabetes-related complications and possibly the impairments in heat loss. Despite this, it is alarming to note the lack of information regarding diabetes and heat stress given the vulnerability of this population. In contrast, few studies have examined the effects of cold exposure on individuals with diabetes with the exception of its therapeutic potential, particularly for type 2 diabetes. This review summarizes the current state of knowledge regarding the impact of diabetes on heat and cold exposure with respect to the core temperature regulation, cardiovascular adjustments and glycemic control while also considering the beneficial effects of maintaining aerobic fitness.

Cold Stress Effects on Exposure Tolerance and Exercise Performance

Cold weather can have deleterious effects on health, tolerance, and performance. This paper will review the physiological responses and external factors that impact cold tolerance and physical performance. Tolerance is defined as the ability to withstand cold stress with minimal changes in physiological strain. Physiological and pathophysiological responses to short-term (cold shock) and long-term cold water and air exposure are presented. Factors (habituation, anthropometry, sex, race, and fitness) that influence cold tolerance are also reviewed. The impact of cold exposure on physical performance, especially aerobic performance, has not been thoroughly studied. The few studies that have been done suggest that aerobic performance is degraded in cold environments. Potential physiological mechanisms (decreases in deep body and muscle temperature, cardiovascular, and metabolism) are discussed. Likewise, strength and power are also degraded during cold exposure, primarily through a decline in muscle temperature. The review also discusses the concept of thermoregulatory fatigue, a reduction in the thermal effector responses of shivering and vasoconstriction, as a result of multistressor factors, including exhaustive exercise.

Sympathetic control of reflex cutaneous vasoconstriction in human aging

This Synthesis highlights a series of recent studies that has systematically interrogated age-related deficits in cold-induced skin vasoconstriction. In response to cold stress, a reflex increase in sympathetic nervous system activity mediates reductions in skin blood flow. Reflex vasoconstriction during cold exposure is markedly impaired in aged skin, contributing to the relative inability of healthy older adults to maintain core temperature during mild cold stress in the absence of appropriate behavioral thermoregulation. This compromised reflex cutaneous vasoconstriction in healthy aging can occur as a result of functional deficits at multiple points along the efferent sympathetic reflex axis, including blunted sympathetic outflow directed to the skin vasculature, reduced presynaptic neurotransmitter synthesis and/or release, and altered end-organ responsiveness at several loci, in addition to potential alterations in afferent thermoreceptor function. Arguments have been made that the relative inability of aged skin to appropriately constrict is due to the aging cutaneous arterioles themselves, whereas other data point to the neural circuitry controlling those vessels. The argument presented herein provides strong evidence for impaired efferent sympathetic control of the peripheral cutaneous vasculature during whole body cold exposure as the primary mechanism responsible for attenuated vasoconstriction.

Cognitive and perceptual responses during passive heat stress in younger and older adults

We tested the hypothesis that attention, memory, and executive function are impaired to a greater extent in passively heat-stressed older adults than in passively heat-stressed younger adults. In a randomized, crossover design, 15 older (age: 69 ± 5 yr) and 14 younger (age: 30 ± 4 yr) healthy subjects underwent passive heat stress and time control trials. Cognitive tests (outcomes: accuracy and reaction time) from the CANTAB battery evaluated attention [rapid visual processing (RVP), choice reaction time (CRT)], memory [spatial span (SSP), pattern recognition memory (PRM)], and executive function [one touch stockings of Cambridge (OTS)]. Testing was undertaken on two occasions during each trial, at baseline and after internal temperature had increased by 1.0 ± 0.2°C or after a time control period. For tests that measured attention, reaction time during RVP and CRT was slower (P ≤ 0.01) in the older group. During heat stress, RVP reaction time improved (P < 0.01) in both groups. Heat stress had no effect (P ≥ 0.09) on RVP or CRT accuracy in either group. For tests that measured memory, accuracy on SSP and PRM was lower (P < 0.01) in the older group, but there was no effect of heat stress (P ≥ 0.14). For tests that measured executive function, overall, accuracy on OTS was lower, and reaction time was slower in the older group (P ≤ 0.05). Reaction time generally improved during heat stress, but there was no effect of heat stress on accuracy in either group. These data indicate that moderate increases in body temperature during passive heat stress do not differentially compromise cognitive function in younger and older adults.

Elderly bioheat modeling: changes in physiology, thermoregulation, and blood flow circulation

A bioheat model for the elderly was developed focusing on blood flow circulatory changes that influence their thermal response in warm and cold environments to predict skin and core temperatures for different segments of the body especially the fingers. The young adult model of Karaki et al. (Int J Therm Sci 67:41-51, 2013) was modified by incorporation of the physiological thermoregulatory and vasomotor changes based on literature observations of physiological changes in the elderly compared to young adults such as lower metabolism and vasoconstriction diminished ability, skin blood flow and its minimum and maximum values, the sweating values, skin fat thickness, as well as the change in threshold parameter related to core or skin temperatures which triggers thermoregulatory action for sweating, maximum dilatation, and maximum constriction. The developed model was validated with published experimental data for elderly exposure to transient and steady hot and cold environments. Predicted finger skin temperature, mean skin temperature, and core temperature were in agreement with published experimental data at a maximum error less than 0.5 °C in the mean skin temperature. The elderly bioheat model showed an increase in finger skin temperature and a decrease in core temperature in cold exposure while it showed a decrease in finger skin temperature and an increase in core temperature in hot exposure.

Hands and feet: physiological insulators, radiators and evaporators

The purpose of this review is to describe the unique anatomical and physiological features of the hands and feet that support heat conservation and dissipation, and in so doing, highlight the importance of these appendages in human thermoregulation. For instance, the surface area to mass ratio of each hand is 4-5 times greater than that of the body, whilst for each foot, it is ~3 times larger. This characteristic is supported by vascular responses that permit a theoretical maximal mass flow of thermal energy of 6.0 W (136 W m(2)) to each hand for a 1 °C thermal gradient. For each foot, this is 8.5 W (119 W m(2)). In an air temperature of 27 °C, the hands and feet of resting individuals can each dissipate 150-220 W m(2) (male-female) of heat through radiation and convection. During hypothermia, the extremities are physiologically isolated, restricting heat flow to <0.1 W. When the core temperature increases ~0.5 °C above thermoneutral (rest), each hand and foot can sweat at 22-33 mL h(-1), with complete evaporation dissipating 15-22 W (respectively). During heated exercise, sweat flows increase (one hand: 99 mL h(-1); one foot: 68 mL h(-1)), with evaporative heat losses of 67-46 W (respectively). It is concluded that these attributes allow the hands and feet to behave as excellent radiators, insulators and evaporators.

Murder or not? Cold temperature makes criminals appear to be cold-blooded and warm temperature to be hot-headed

Temperature-related words such as cold-blooded and hot-headed can be used to describe criminal behavior. Words associated with coldness describe premeditated behavior and words associated with heat describe impulsive behavior. Building on recent research about the close interplay between physical and interpersonal coldness and warmth, we examined in a lab experiment how ambient temperature within a comfort zone influences judgments of criminals. Participants in rooms with low temperature regarded criminals to be more cold-blooded than participants in rooms with high temperature. Specifically, they were more likely to attribute premeditated crimes, ascribed crimes resulting in higher degrees of penalty, and attributed more murders to criminals. Likewise, participants in rooms with high temperature regarded criminals to be more hot-headed than participants in rooms with low temperature: They were more likely to attribute impulsive crimes. Results imply that cognitive representations of temperature are closely related to representations of criminal behavior and attributions of intent.

Age-related decline in thermal adaptation capacities: an evoked potentials study

Aging is associated with changes in thermosensitivity and decreases in the functionality of the autonomic thermoregulation. The underlying mechanisms are, however, not fully understood. Elderly subjects may undergo functional changes in the integration process of the thermal sensory system, especially in their thermal adaptation capacities. To verify this hypothesis, we compared thermal evoked responses in younger and older subjects exposed to thermoneutral (27 °C) and warm (30 °C) environments. In the warm environment, the amplitudes of thermal evoked potentials (EPs) were significantly lower in older than in younger subjects, whereas in the thermoneutral environment, the EP amplitudes were similar in both groups. These findings suggest that thermal adaptation capacities are reduced in elderly individuals, due to a dysfunction of C-fibers with aging, particularly expressed by lowered adaptation capacities to temperature variations.

Measuring energy expenditure in clinical populations: rewards and challenges

The measurement of energy expenditure (EE) is recommended as an important component of comprehensive clinical nutrition assessments in patients with altered metabolic states, who failed to respond to nutrition support and with critical illness that require individualized nutrition support. There is evidence that EE is variable in patients with metabolic diseases, such as chronic renal disease, cirrhosis, HIV, cancer cachexia, cystic fibrosis and patients under intensive care. By using appropriate techniques and interpretations of basal or resting EE, clinicians can facilitate the adequate nutrition support with minimum negative impacts from under- or overfeeding in these patients. This review is based on our current understanding of the different components of EE and the techniques to measure them, and to re-examine advances and challenges to determine energy needs in clinical populations with more focuses on the obese, pediatric and elderly patients. In addition, technological advances have expanded the choices of market-available equipments for assessing EE, which also bring specific challenges and rewards in selecting the right equipment with specific performance criteria. Lastly, analytical considerations of interpreting the results of EE in the context of changing body composition are presented and discussed.

Human temperature regulation when given the opportunity to behave

This study aimed to test the primary hypotheses that human thermoregulatory behavior is: (1) initiated before changes in rectal or esophageal temperatures; and (2) accompanied by indiscernible differences in sweating or shivering. This was achieved by placing nine, healthy, males in a situation where they were free to move between a cold (~8 °C) and a hot (~46 °C) environment. Upon behaving [i.e., move from cold to hot (C→H) or from hot to cold (H→C)], skin, rectal, and esophageal temperatures, indices of cutaneous vasomotor tone, metabolism and evaporation, and local and whole-body thermal discomfort were recorded. Rectal temperatures were similar at H→C (37.1 ± 0.2 °C) and C→H (37.1 ± 0.2 °C); yet esophageal temperatures were higher at C→H (36.9 ± 0.2 vs. 36.8 ± 0.2 °C). Skin temperature (C→H, 28.4 ± 0.9 vs. H→C, 35.0 ± 0.6 °C) and vasomotor tone were drastically different upon the decision to behave. Metabolic heat production was lower at H→C (79 ± 10 W/m(2)) than at C→H (101 ± 20 W/m(2)), yet there were no statistical differences in evaporative heat loss (C→H, 23 ± 33 W/m(2) vs. H→C, 52 ± 36 W/m(2)). Whole-body thermal discomfort was similar at C→H and H→C, yet there were inter-segmental differences. These findings indicate that skin temperature, not core temperature, plays a signaling role in the decision to behaviorally thermoregulate. However, this behavior does not occur in the complete absence of autonomic thermoregulatory responses.

Validating the Adolescent/Adult Sensory Profile and Examining its Ability to Screen Sensory Processing Difficulties among Israeli People

Purpose:

The purpose of this study was to (1) validate the Hebrew version of the Adolescent/Adult Sensory Profile (AASP); (2) screen sensory processing difficulties, as expressed in daily living in a vast range of ages of healthy Israeli adolescents, adults and older people; and (3) examine gender effect on sensory processing in the different age groups.

Findings:

Good internal consistency was found for each of the AASP quadrants, although factor analysis did not find total similarity between the Hebrew version of the AASP and the original AASP. Sensory processing difficulties were shown by 22–42% of the participants in the different age groups. Older participants had lower tendency for Sensation Seeking. Females were more sensitive than males in the age groups of 11–17 years and 18–64 years.

Conclusion:

In general, the Hebrew version of the AASP was found to be valid and succeeded in profiling sensory processing difficulties along the life span of typical Israeli adolescents and adults. Further studies should apply the Hebrew version of the AASP to screen sensory processing difficulties among individuals with disabilities and elaborate their impact on people's performance/participation in daily activities.

Resting blood flow in the skin: does it exist, and what is the influence of temperature, aging, and diabetes?

Measurement of resting blood flow to the skin and other organs is an important indicator of health and disease and a way to assess the reaction to various stimuli and pharmaceutical interventions. However, unlike plasma ions such as sodium or potassium, it is difficult to determine what the proper value for resting blood flow really is. Part of the problem is in the measurement of blood flow; various techniques yield very different measures of skin blood flow even in the same area. Even if there were common techniques, resting blood flow to tissue, such as the skin, is determined by the interaction of a plurality of factors, including the sympathetic nervous system, temperature, pressure, shear forces on blood vessels, tissue osmolality, and a variety of other stimuli. Compounding this variability, the blood flow response to any stressor is reduced by free radicals in the blood and diminished by aging and diabetes. Race also has an effect on resting blood flow to the skin. All these factors interact to make the exact resting blood flow difficult to determine in any one individual and at any one time. This review examines the main techniques to assess blood flow, the factors that alter blood flow in the skin, and how aging and diabetes affect blood flow. Recommendations for the measurement of resting blood flow are presented.

The effects of temperature on service employees' customer orientation: an experimental approach

Numerous studies have demonstrated how temperature can affect perceptual, cognitive and psychomotor performance (e.g. Hancock, P.A., Ross, J., and Szalma, J., 2007. A meta-analysis of performance response under thermal stressors. Human Factors: The Journal of the Human Factors and Ergonomics Society, 49 (5), 851-877). We extend this research to interpersonal aspects of performance, namely service employees' and salespeople's customer orientation. We combine ergonomics with recent research on social cognition linking physical with interpersonal warmth/coldness. In Experiment 1, a scenario study in the lab, we demonstrate that student participants in rooms with a low temperature showed more customer-oriented behaviour and gave higher customer discounts than participants in rooms with a high temperature - even in zones of thermal comfort. In Experiment 2, we show the existence of alternative possibilities to evoke positive temperature effects on customer orientation in a sample of 126 service and sales employees using a semantic priming procedure. Overall, our results confirm the existence of temperature effects on customer orientation. Furthermore, important implications for services, retail and other settings of interpersonal interactions are discussed. Practitioner Summary: Temperature effects on performance have emerged as a vital research topic. Owing to services' increasing economic importance, we transferred this research to the construct of customer orientation, focusing on performance in service and retail settings. The demonstrated temperature effects are transferable to services, retail and other settings of interpersonal interactions.

The grey mouse lemur: a non-human primate model for ageing studies

The use of non-human primate models is required to understand the ageing process and evaluate new therapies against age-associated pathologies. The present article summarizes all the contributions of the grey mouse lemur Microcebus murinus, a small nocturnal prosimian primate, to the understanding of the mechanisms of ageing. Results from studies of both healthy and pathological ageing research on the grey mouse lemur demonstrated that this animal is a unique model to study age-dependent changes in endocrine systems, biological rhythms, thermoregulation, sensorial, cerebral and cognitive functions.

The interrealtionship between locally applied heat, ageing and skin blood flow on heat transfer into and from the skin

In response to a thermal stress, skin blood flow (BF) increases to protect the skin from damage. When a very warm, noxious, heat source (44 °C) is applied to the skin, the BF increases disproportionately faster than the heat stress that was applied, creating a safety mechanism for protecting the skin. In the present investigation, the rate of rise of BF in response to applied heat at temperatures between 32 °C and 40 °C was examined as well as the thermal transfer to and from the skin with and without BF in younger and older subjects to see how the skin responds to a non-noxious heat source. Twenty male and female subjects (10 - 20-35 years, 10 - 40-70 years) were examined. The arms of the subjects were passively heated for 6 min with and without vascular occlusion by a thermode at temperatures of 32, 36, 38 or 40 °C. When occlusion was not used during the 6 min exposure to heat, there was an exponential rise in skin temperature and BF in both groups of subjects over the 6-min period. However, the older subjects achieved similar skin temperatures but with the expenditure of fewer calories from the thermode than was seen for the younger subjects (p<0.05). BF was significantly less in the older group than the younger group at rest and after exposure to each of the three warmest thermode temperatures (p<0.05). As was seen for noxious temperatures, after a delay, the rate of rise of BF at the three warmest thermode temperatures was faster than the rise in skin temperature in the younger group but less in the older group of subjects. Thus, a consequence of ageing is reduced excess BF in response to thermal stress increasing susceptibility to thermal damage. This must be considered in modelling of BF.

The ability of the skin to absorb heat; the effect of repeated exposure and age

Background

When heat is applied to the skin, it is dissipated due to conductive heat flow in the tissue and the blood. While heat flow has been studied after applying a single heat exposure, the physiology of repeated exposures to local heat has not been well investigated.

Material/Methods

Twenty male and female subjects in the age range of 20–65 years old participated in a series of experiments during which a thermode was placed on their leg above the quadriceps muscle for 20 minutes, and on 3 sequential days, to see the effect of repeated local heat on skin blood flow, skin temperature, and on caloric transfer from a thermode used to raise skin temperature.

Results

The results of the experiment showed that, for young subjects, to raise skin temperature to 40 degrees C required more than double the calories required in older subjects. Further, in the younger subjects, the blood flow response in the first 20 minutes of heat exposure was over 30% higher than that seen in the older subjects. However, on the 2nd and 3rd day, the blood flow response of the younger subjects, was not significantly different between day 2 and 3, but was significantly less than day 1. There was no statistical difference in the blood flow response between day 1, 2 and 3 in the older subjects. In the younger subjects, in the 2 and 3^rd day, the number of calories needed to warm the skin was also significantly less than that seen in the first day.

Conclusions

In younger subjects but not older subjects, there appears to be some degree of acclimatization with an enhanced blood flow response in the first day that was protective to the skin which was not seen in repeated heat exposure.

Relationship Between Pain Catastrophizing Level and Sensory Processing Patterns in Typical Adults

OBJECTIVE. We examined the relationship between pain perception, as expressed by pain catastrophizing level, and sensory processing patterns among typical adults.

METHOD. Two hundred ninety healthy adults participated in this study: 138 men and 152 women. Their ages ranged from 18 to 50 (mean age = 30.2 ± 6.8). All participants completed the Adolescent/Adult Sensory Profile and the Pain Catastrophizing Scale (PCS).

RESULTS. PCS scores significantly correlated with Low Registration, Sensory Sensitivity, and Sensation Avoiding. Women had higher sensory sensitivity and a higher pain catastrophizing level than did men.

CONCLUSION. Sensory processing patterns may be related to individual pain perception, as expressed in pain catastrophizing level. Intervention programs should take these factors into account to be more focused on the specific needs of each client, facilitate his or her optimal engagement in daily living activities, and elevate well-being.

Thermal sensitivity in the elderly: a review

Aging is associated with a progressive decrease in thermal perception, as revealed by increased thermal detection thresholds in the elderly. This reduction in thermosensitivity follows a distal-proximal pattern, with more pronounced decrements observed in the limbs and in the perception of warmth vs. cold. The main underlying causes of this seem to be aging of the skin and subsequent reductions in thermoreceptor density and superficial skin blood flow. However, the results from some animal studies also suggest that changes in the peripheral nerve system, particularly fiber loss and decreased conduction velocity, may also be involved. In this paper, we review age-related changes in the thermal sensitivity of humans, their underlying mechanisms, and the strengths and limitations of some of the methodologies used to assess these changes.

The contribution of skin blood flow in warming the skin after the application of local heat; the duality of the Pennes heat equation

As predicted by the Pennes equation, skin blood flow is a major contributor to the removal of heat from an external heat source. This protects the skin from erythema and burns. But, for a person in a thermally neutral room, the skin is normally much cooler than arterial blood. Therefore, if skin blood flow (BF) increases, it should initially warm the skin paradoxically. To examine this phenomenon, 10 young male and female subjects participated in a series of experiments to examine the contribution of skin blood flow in the initial warming the skin after the application of local heat. Heat flow was measured by the use of a thermode above the brachioradialis muscle. The thermode was warmed by constant temperature water at 44°C entering the thermode at a water flow rate of 100 cm(3)/min. Skin temperature was measured by a thermistor and blood flow in the underlying skin was measured by a laser Doppler imager in single point mode. The results of the experiments showed that, when skin temperature is cool (31-32°C), the number of calories being transferred to the skin from the thermode cannot account for the rise in skin temperature alone. A significant portion of the rise in skin temperature is due to the warm arterialized blood traversing the skin from the core areas of the body. However, as skin temperature approaches central core temperature, it becomes less of a heat source and more of a heat sync such that when skin temperature is at or above core temperature, the blood flow to the skin, as predicted by Pennes, becomes a heat sync pulling heat from the thermode.

Effects of season on sleep and skin temperature in the elderly

The effects of season on sleep and skin temperature (Tsk) in 19 healthy, elderly volunteers were investigated. Measurements were obtained in summer, winter, and fall, and activity levels were monitored using a wrist actigraph system for five consecutive days. The temperature and humidity of the bedrooms of the subjects' homes were measured continuously for five days. During actigraphic measurement, Tsk during sleep was measured for two nights. The bedroom temperature and humidity significantly increased in summer compared to winter and fall. In summer, the total sleep time decreased (mean +/- SE min; summer, 350.8 +/- 15.7; winter, 426.5 +/- 14.2; fall, 403.2 +/- 16.4) and wakefulness increased (P < 0.003) compared to those in fall or winter. The sleep efficiency index that was derived from wrist actigraphy was significantly decreased (P < 0.001) in summer (81.4 +/- 2.9%) compared with winter (91.6 +/- 1.3%) or fall (90.2 +/- 1.2%). The forehead Tsk significantly increased, while the chest and thigh Tsks were decreased in summer compared to those in fall or winter. These results suggest that, in the elderly, sleep is disturbed in summer more than in other seasons, and that this disturbance is related to fluctuations in Tsk.

Field study on behaviors and adaptation of elderly people and their thermal comfort requirements in residential environments

This study investigated the thermal sensation of elderly people in Taiwan, older than 60 years, in indoor microclimate at home, and their requirements for establishing thermal comfort. The study was conducted using both a thermal sensation questionnaire and measurement of indoor climatic parameters underlying the thermal environment. Survey results were compared with those reported by Cheng and Hwang (2008, J. Tongji Univ., 38, 817-822) for non-elders to study the variation between different age groups in requirements of indoor thermal comfort. The results show that the predominant strategy of thermal adaptation for elders was window-opening in the summer and clothing adjustment in the winter. The temperature of thermal neutrality was 25.2 degrees C and 23.2 degrees C for the summer and the winter, respectively. Logistically regressed probit modeling on percentage of predicted dissatisfied (PPD) against mean thermal sensation vote revealed that the sensation votes corresponding to a PPD of 20% were +/- 0.75 for elders, about +/- 0.10 less than the levels projected by ISO 7730 model. The range of operative temperature for 80% thermal acceptability for elders in the summer was 23.2-27.1 degrees C, narrower than the range of 23.0-28.6 degrees C reported for non-elders. This is likely a result of a difference in the selection of adaptive strategies.

PRACTICAL IMPLICATIONS

Taiwan in the last decade has seen a rapid growth in the elderly population in its societal structure, and as such the quality of indoor thermal comfort increasingly concerns the elderly people. This study presents the results from field-surveying elders residing in major geographical areas of Taiwan, and discusses the requirements of these elders for indoor thermal comfort in different seasons. Through a comparison with the requirements by non-elders, this study demonstrates the unique sensitivity of elders toward indoor thermal quality and the selection of adaptive strategies that need to be considered when a thermal comfort zone is attempted in a household of members consisting of different age groups.

Hypothermia in the geriatric population

Hypothermia is common in the geriatric population and its significance perhaps under-recognized. Hypothermia is associated with substantial morbidity and fatality, but to some extent is preventable provided caregivers and providers of healthcare to older adults adopt preventive measures to lower its occurrence. Hypothermia occurs in both cold and warm settings; its pathogenesis involves alterations in the age-related physiology of thermoregulation, along with a variable combination of environmental factors, disease processes and medications, many of which are recognizable. Once diagnosed, treatment must be prompt and aggressive, and must consider several options for rewarming. Education of healthcare providers regarding early recognition of hypothermia and a better understanding of preventive and treatment measures will undoubtedly lower complications of hypothermia in affected elderly.

American College of Sports Medicine position stand: prevention of cold injuries during exercise

It is the position of the American College of Sports Medicine that exercise can be performed safely in most cold-weather environments without incurring cold-weather injuries. The key to prevention is use of a comprehensive risk management strategy that: a) identifies/assesses the cold hazard; b) identifies/assesses contributing factors for cold-weather injuries; c) develops controls to mitigate cold stress/strain; d) implements controls into formal plans; and e) utilizes administrative oversight to ensure controls are enforced or modified. The American College of Sports Medicine recommends that: 1) coaches/athletes/medical personnel know the signs/symptoms and risk factors for hypothermia, frostbite, and non-freezing cold injuries, identify individuals susceptible to cold injuries, and have the latest up-to-date information about current and future weather conditions before conducting training sessions or competitions; 2) cold-weather clothing be chosen based on each individual's requirements and that standardized clothing ensembles not be mandated for entire groups; 3) the wind-chill temperature index be used to estimate the relative risk of frostbite and that heightened surveillance of exercisers be used at wind-chill temperatures below -27 degrees C (-18 degrees F); and 4) individuals with asthma and cardiovascular disease can exercise in cold environments, but should be monitored closely.