Thermal sensitivity in the elderly: a review

Cardiovascular responses to heat and cold exposure are altered by preterm birth in guinea pigs

Adversity early in life can modify the trajectory for disease risk extending decades beyond the event. Preterm birth produces persistent cardiovascular alterations that may appear maladaptive in adulthood. We have previously hypothesized that those born preterm may exhibit cardiovascular vulnerability in the climate change context. Further, this vulnerability may be present as early as childhood. We aimed to identify the early signs of cardiovascular dysfunction at childhood-equivalent age using our animal model of preterm birth. Using a whole-body thermal stress test, guinea pigs aged 35-d and 38-d (equivalent to 8-10-year-old children) and born at term or preterm gestations were exposed to progressive hyper- (TC = 41.5°C) and hypo-thermia (TC = 34°C; normothermia TC = 39°C). Comprehensive cardiovascular monitoring included ECG, blood pressure, microvascular perfusion, blood gas, and catecholamine profile, as well as skin and core body temperature. Preterm-born animals exhibited attenuated vascular responses to hyperthermic stress, and a significant elevation in systolic blood pressure in response to hypothermic stress. Such responses are similar to those observed in elderly populations and indicate the presence of cardiovascular dysfunction. This is the first study to demonstrate the impact of preterm birth on the cardiovascular response to both heat and cold stress. Further, this dysfunction has been observed at an earlier age than that achievable using traditional stress testing techniques. The present findings warrant further investigation.

The effect of alcohol consumption on human physiological and perceptual responses to heat stress: a systematic scoping review

BACKGROUND

Ethyl alcohol (ethanol) consumption is ostensibly known to increase the risk of morbidity and mortality during hot weather and heatwaves. However, how alcohol independently alters physiological, perceptual, and behavioral responses to heat stress remains poorly understood. Therefore, we conducted a systematic scoping review to understand how alcohol consumption affects thermoregulatory responses to the heat.

METHODS

We searched five databases employing the following eligibility criteria, studies must have: 1) involved the oral consumption of ethanol, 2) employed a randomized or crossover-control study design with a control trial consisting of a volume-matched, non-alcoholic beverage, 3) been conducted in healthy adult humans, 4) reported thermophysiological, perceptual, hydration status markers, and/or behavioral outcomes, 5) been published in English, 6) been conducted in air or water at temperatures of > 28°C, 7) involved passive rest or exercise, and 8) been published before October 4th, 2023.

RESULTS

After removing duplicates, 7256 titles were screened, 29 papers were assessed for eligibility and 8 papers were included in the final review. Across the 8 studies, there were a total of 93 participants (93 male/0 female), the average time of heat exposure was 70 min and average alcohol dose was 0.68 g·kg1. There were 23 unique outcome variables analyzed from the studies. The physiological marker most influenced by alcohol was core temperature (lowered with alcohol consumption in 3/4 studies). Additionally, skin blood flow was increased with alcohol consumption in the one study that measured it. Typical markers of dehydration, such as increased urine volume (1/3 studies), mass loss (1/3 studies) and decreased plasma volume (0/2 studies) were not consistently observed in these studies, except for in the study with the highest alcohol dose.

CONCLUSION

The effect of alcohol consumption on thermoregulatory responses is understudied, and is limited by moderate doses of alcohol consumption, short durations of heat exposure, and only conducted in young-healthy males. Contrary to current heat-health advice, the available literature suggests that alcohol consumption does not seem to impair physiological responses to heat in young healthy males.

Hot topic: Mapping of the human intranasal mucosal thermal sensitivity: A clinical study on thermal threshold and trigeminal receptors

INTRODUCTION

The olfactory and trigeminal system are closely interlinked. Existing literature has primarily focused on characterizing trigeminal stimulation through mechanical and chemical stimulation, neglecting thermal stimulation thus far. The present study aimed to characterize the intranasal sensitivity to heat and the expression of trigeminal receptors (transient receptor potential channels, TRP).

METHODS

A total of 20 healthy participants (aged 21-27 years, 11 women) were screened for olfactory function and trigeminal sensitivity using several tests. Under endoscopic control, a thermal stimulator was placed in 7 intranasal locations: anterior septum, lateral vestibulum, interior nose tip, lower turbinate, middle septum, middle turbinate, and olfactory cleft to determine the thermal threshold. Nasal swabs were obtained in 3 different locations (anterior septum, middle turbinate, olfactory cleft) to analyze the expression of trigeminal receptors TRP: TRPV1, TRPV3, TRPA1, TRPM8.

RESULTS

The thermal threshold differed between locations (p = 0.018), with a trend for a higher threshold at the anterior septum (p = 0.092). There were no differences in quantitative receptor expression (p = 0.46) at the different sites. The highest overall receptor RNA expression was detected for TRPV1 over all sites (p<0.001). The expression of TRPV3 was highest at the anterior septum compared to the middle turbinate or the olfactory cleft. The thermal sensitivity correlated with olfactory sensitivity and results from tests were related to trigeminal function like intensity ratings of ammonium, a questionnaire regarding trigeminal function, nasal patency, and CO2 thresholds. However, no correlation was found between receptor expression and psychophysical measures of trigeminal function.

DISCUSSION

This study provided the first insights about intranasal thermal sensitivity and suggested the presence of topographical differences in thermal thresholds. There was no correlation between thermal sensitivity and trigeminal mRNA receptor expression. However, thermal sensitivity was found to be associated with psychophysical measures of trigeminal and olfactory function.

Early detection of altered cold perception in elderly with type 2 diabetes using a novel Quantitative Sensory Testing method

AIM

To compare the effectiveness of two methods for measuring cold detection thresholds in screening for temperature-perception deficits in elderly individuals with type 2 diabetes (T2 diabetes).

METHODS

Cold threshold measurements were performed on seven body regions of participants with diabetes without neuropathy (n = 30; mean age, 70.9 ± 6.5 years) and healthy participants (n = 73; mean age, 68 ± 5 years). Two protocols applying the Levels Method were used: the first used skin temperature as the starting point; the second used 40 °C.

RESULTS

Cold detection thresholds were significantly higher in subjects with diabetes, particularly on the foot. For CDT TSk, values were -2.22 ± 1.91 °C in non-diabetic and -3.27 ± 3.33 °C in diabetic groups (p = 0.023); for CDT 40, values were -9.82 ± 3.5 °C and -12.18 ± 4.5 °C (p = 0.003). However, after adjusting for age, the group effect on cold threshold with skin temperature as baseline disappeared. Sensory screens showed that the Area Under Curve of the method using a 40 °C baseline was 0.69 (p = 0.002).

CONCLUSION

Measuring the cold detection threshold on the foot with a 40 °C baseline is more effective than using skin temperature as a baseline for screening sensory alterations in elderly subjects with type 2 diabetes before neuropathy onset.

SIGNIFICANCE

These findings highlight the importance of selecting the appropriate cold detection threshold method for elderly individuals with type 2 diabetes. The optimal method can facilitate early identification of sensory changes, minimizing complications and improving overall well-being.

Burning Question: How Does Our Brain Process Positive and Negative Cues Associated with Thermosensation?

Whether it is the dramatic suffocating sensation from a heat wave in the summer or the positive reinforcement arising from a hot drink on a cold day; we can certainly agree that our thermal environment underlies our daily rhythms of sensation. Extensive research has focused on deciphering the central circuits responsible for conveying the impact of thermogenesis on mammalian behavior. Here, we revise the recent literature responsible for defining the behavioral correlates that arise from thermogenic fluctuations in mammals. We transition from the physiological significance of thermosensation to the circuitry responsible for the autonomic or behavioral responses associated with it. Subsequently, we delve into the positive and negative valence encoded by thermoregulatory processes. Importantly, we emphasize the crucial junctures where reward, pain, and thermoregulation intersect, unveiling a complex interplay within these neural circuits. Finally, we briefly outline fundamental questions that are pending to be addressed in the field. Fully deciphering the thermoregulatory circuitry in mammals will have far-reaching medical implications. For instance, it may lead to the identification of novel targets to overcome thermal pain or allow the maintenance of our core temperature in prolonged surgeries.

Spatial and temporal indoor temperature differences at home and perceived coldness in winter: A cross-sectional analysis of the nationwide Smart Wellness Housing survey in Japan

Residents themselves are responsible for controlling their living environment, and their perception of coldness is important to protect their health. Although previous studies examined the association between perceived coldness and indoor temperature, they did not consider the spatial-temporal differences in indoor temperatures. This study, conducted in Japan, measured indoor temperatures in 1,553 houses across several rooms (living room, changing room, and bedroom) and heights (at 1 m above the floor and near the floor) over two weeks and obtained the perceived coldness from 2,793 participants during winter. Results showed substantial temperature differences between rooms (horizontal differences): 3.8 °C between living and changing rooms, and 4.1 °C between living rooms and bedrooms. The average vertical and diel (evening-morning) temperature differences in the living room were 3.1 °C and 3.0 °C, respectively. Regional analysis revealed that the Tohoku region experienced larger horizontal and diel indoor temperature differences, primarily due to its practice of intermittent and partial heating in living rooms only, in contrast to Hokkaido's approach of heating the entire house continuously. Despite Hokkaido's comprehensive heating system, it exhibited the largest vertical temperature difference of 5.1 °C in living rooms, highlighting the insufficiency of heating alone and the necessity for enhanced thermal insulation. The multivariate logistic regression analyses showed that average temperatures and vertical temperature differences were associated with perceived coldness, while horizontal and diel differences did not show a significant association, further emphasizing the importance of improved thermal insulation. Moreover, factors like individual attributes (age and gender), and lifestyle choices (meal quantity, exercise habits, alcohol consumption, and clothing amount) were significantly associated with coldness perception. Notably, older adults were less likely to perceive coldness but more vulnerable to the health impacts of low temperatures, underscoring the necessity of not solely relying on human perception for indoor temperature management to protect cold-related health problems.

Interaction between local blood flow and tolerance to prolonged pain in the elderly

PURPOSE

We aimed to explore the link between local vasodilation and pain perception in elderly subjects, testing the hypothesis that altered local cutaneous blood flow participates in the decrease in pain tolerance with age.

METHOD

Sixty-eight young and 83 older participants performed a pain tolerance test in which they hold their hand in an airtight box in which air temperature was regulated at 65 °C until the pain became unbearable. Participants continuously estimated pain intensity. Skin temperature and local blood flow in the box-exposed hand were continuously monitored.

RESULTS

In the young group, 97% of subjects resisted pain until the end of the test, whereas only 53% in the elderly group managed to do so, indicating that pain tolerance is impaired in the elderly. Among all participants, the skin temperature associated with the first pain sensation was below the threshold for nociceptor activation (43 °C). Interestingly, blood flow in the elderly group was correlated with pain judgment, whereas no such correlation was observed in the young.

CONCLUSION

Our results suggest that the local vasodilator response induced by local heating may be involved in pain perception and may influence thermal pain tolerance with aging. These results could contribute to a better understanding of vascular deficits and the development of chronic pain in vascular pathologies.

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.

Consumption of hot protein-containing drink accelerates gastric emptying rate and is associated with higher hunger levels in older adults

Meal temperature is known to affect gastric emptying and appetite. While protein intake is recommended for older age, gastric emptying is delayed with age, resulting in loss of appetite. This study aimed to investigate whether adjusting the temperature of protein-containing drinks could improve gastric emptying and appetite in older individuals. Twenty male and female participants aged 65 years and older underwent three one-day trials in random order. Participants visited the laboratory after a 10-hour fast and consumed 200 mL of protein-containing drink dissolved in 13C-sodium acetate at 4°C, 37°C, or 60°C in a 3-minute period. Then, participants sat in a chair for 90 minutes to measure gastric emptying rate by the 13C-sodium acetate breath test and subjective appetite by a visual analog scale. The results showed that 37°C and 60°C drinks had faster gastric emptying at 5 and 10 min after ingestion than did the 4°C drink (trial-time interaction, p = 0.014). Tmax-calc, an indicator of gastric emptying rate, tended to be faster for the 37°C and 60°C drinks than for the 4°C drink (49.7 ± 17.5 min vs. 44.1 ± 18.5 min vs. 45.3 ± 25.8 min for the 4°C, 37°C, and 60°C, respectively; p = 0.085). There were no significant differences in the change in hunger from baseline among the three different temperature drinks (p > 0.05). Only in the 60°C trial, a shorter gastric emptying time was associated with greater hunger (r=-0.554, p = 0.021). These findings suggest that hot protein-containing drinks may accelerate gastric emptying and contribute to rapid nutrient intake and increased appetite in older adults.

Thermal modulation of skin friction at the finger pad

Preliminary human studies show that reduced skin temperature minimises the risk of mechanically induced skin damage. However, the mechanisms by which cooling enhances skin tolerance to pressure and shear remain poorly understood. We hypothesized that skin cooling below thermo-neutral conditions will decrease kinetic friction at the skin-material interface. To test our hypothesis, we measured the friction coefficient of a thermally pre-conditioned index finger pad sliding at a normal load (5N) across a plate maintained at three different temperatures (38, 24, and 16 °C) in 8 healthy young adults (29±5y). To quantify the temperature distribution of the skin tissue, we used 3D surface scanning and Optical Coherence Tomography to develop an anatomically representative thermal model of the finger. Our group-level data indicated that the sliding finger with thermally affected tissues (up to 8 mm depth) experienced significantly lower frictional forces (p<0.01) at plate temperatures of 16 °C (i.e. 32% decrease) and 24 °C (i.e. 13% decrease) than at 38 °C, respectively. This phenomenon occurred consistently across participants (i.e. N = 6/8, 75%) and without large changes in skin hydration during sliding. Our complementary experimental and theoretical results provide new insights into thermal modulation of skin friction that can be employed for developing thermal technologies to maintain skin integrity under mechanical loading and shearing.

Regular physical activity across the lifespan to build resilience against rising global temperatures

Population aging, high prevalence of non-communicable diseases, physical inactivity, and rising global temperatures are some of the most pressing issues in public health of the current century. Such trends suggest that individuals increasingly less equipped to tolerate heat will be increasingly exposed to it, which from a public health perspective is alarming. Nonetheless, future impacts of extreme heat events will depend not only on the magnitude of climate change, but on our ability to adapt by becoming less sensitive and vulnerable. Although physical activity's role in mitigating climate change has received attention, its potential contribution to climate change adaptation and resilience remains largely unaddressed. Accordingly, in this viewpoint, we discuss how regular physical activity throughout life could have an important contribution to adapting to rising global temperatures, allowing to be better equipped to cope with heat-related health hazards and increasing individual and community resilience. This viewpoint constitutes a call for more research into the contribution that physical activity can have in adapting to rising global temperatures and, more broadly, to climate change.

Age-Related Difference in Cognitive Performance under Severe Whole-Body Hyperthermia Parallels Cortisol and Physical Strain Responses

Background and Objectives: To date, understanding age-related changes in cognitive processes during heat exposure still needs to be better-understood. Thus, the main aim of the current study was to evaluate the effects of whole-body hyperthermia (WBH), i.e., a ≈ 2.5 °C increase in rectal temperature (Tre) from overnight-fast baseline value, on cognitive functioning in old and young men and to explore factors, such as stress and thermophysiological strain, that could influence such changes. Materials and Methods: Ten young (19-21 years of age) and nine old (61-80 years of age) healthy men underwent an experimental trial with passive lower-body heating in hot water immersion (HWI) at 43 °C (HWI-43 °C) until Tre reached 39 °C in old adults and 39.5 °C in young adults. Cognitive performance and cortisol concentration were assessed before and after HWI, and the physiological strain index (PSI) was assessed during HWI-43 °C. Results: PSI was lower and cortisol concentration was greater after HWI-43 °C in the old group compared with the young group (p < 0.05). Surprisingly, hyperthermia improved cognitive flexibility only in old adults, whereas short-term and visual recognition memories were maintained in both age groups. Conclusions: A ≈ 2.5 °C increase in rectal temperature can improve executive function in old adults, and this increase parallels the increased cortisol concentration and the lower thermophysiological strain under severe WBH conditions.

Relationship between Cognitive Impairment and Depressive Symptoms with Somatosensory Functions in Diabetic and Non-Diabetic Older Adults and Its Impact on Quality of Life

Aging is an inevitable process that impacts the peripheral and central nervous systems and is considered one of the strongest risk factors for neurodegenerative diseases. In addition, when it also presents with diabetes mellitus, the risk of neurological damage may be further increased. This current study aimed to explore the relationships between peripheral sensory system decline and cognitive functions, the symptoms of depression, and quality of life (QoL) as metrics of central nervous system impairment in institutionalized older adults. A total of 95 individuals participated in this case-control study, which included diabetics and non-diabetics. The superficial sensory pathway was assessed in terms of thermal sensation, nociception, and non-discriminative touch, and the deep sensory pathway was evaluated by assessing vibration and light touch-pressure sensations. To assess function at the intellectual level, the Mini-Mental State Examination (MMSE) and Trail Making Test (TMT) cognitive functional tests were used, while the symptoms of depression and QoL were explored by employing the Yesavage Geriatric Depression Scale and EuroQol 5D questionnaire (EQ-5D), respectively. In the overall population analyses, altered thermal sensation was significantly associated with cognitive impairment (CI; p < 0.05). In turn, bivariate analyses and a binary logistic regression showed that the symptoms of depression and QoL were significantly related to altered vibratory sensation when assessed using a medical tuning fork (p < 0.05). In the group of diabetic patients, those with CI also had significantly lower thermal sensation (p < 0.05) and non-discriminative touch sensation, although this was only a trend (p = 0.055). Diabetics with depression had a significantly worse non-discriminative touch (p < 0.05) and vibratory sensation when tested with a tuning fork (p < 0.05). In addition, poorer QoL was associated with reduced sensitivity to heat (p < 0.05), light touch pressure (p < 0.05), and vibrations when assessed either with a tuning fork (p < 0.05) or a biothesiometer (p < 0.05). In contrast, no relationships were found between sensory functions and cognitive assessments in non-diabetic patients. These findings indicate that superficial sensitivity damage was related to CI, while deep sensation alterations were related to depression and poor QoL, with diabetes apparently further strengthening these relationships.

The Contribution of TRPA1 to Corneal Thermosensitivity and Blink Regulation in Young and Aged Mice

The role of TRPA1 in the thermosensitivity of the corneal cold thermoreceptor nerve endings was studied in young and aged mice. The contribution of the TRPA1-dependent activity to basal tearing and thermally-evoked blink was also explored. The corneal cold thermoreceptors' activity was recorded extracellularly in young (5-month-old) and aged (18-month-old) C57BL/6WT (WT) and TRPA1-/- knockout (TRPA1-KO) mice at basal temperature (34 °C) and during cooling (15 °C) and heating (45 °C) ramps. The blink response to cold and heat stimulation of the ocular surface and the basal tearing rate were also measured in young animals using orbicularis oculi muscle electromyography (OOemg) and phenol red threads, respectively. The background activity at 34 °C and the cooling- and heating-evoked responses of the cold thermoreceptors were similar in WT and TRPA1-KO animals, no matter the age. Similar to the aged WT mice, in the young and aged TRPA1-KO mice, most of the cold thermoreceptors presented low frequency background activity, a low cooling threshold, and a sluggish response to heating. The amplitude and duration of the OOemg signals correlated with the magnitude of the induced thermal change in the WT but not in the TRPA1-KO mice. The basal tearing was similar in the TRPA1-KO and WT mice. The electrophysiological data suggest that the TRPA1-dependent nerve activity, which declines with age, contributes to detecting the warming of the ocular surface and also to integrating the thermally-evoked reflex blink.

Preterm-born individuals: a vulnerable population at risk of cardiovascular morbidity and mortality during thermal extremes?

NEW FINDINGS

What is the topic of this review? Thermal extremes disproportionately affect populations with cardiovascular conditions. Preterm birth, across all gestational age ranges below 37 weeks, has been identified as a non-modifiable risk factor for cardiovascular disease. The hypothesis is presented that individuals born preterm are at an increased risk of cardiovascular morbidity and mortality during thermal extremes. What advances does it highlight? Cardiovascular stress tests performed in preterm-born populations, from infancy through adulthood, highlight a progression of cardiovascular dysfunction accelerating through adolescence and adulthood. This dysfunction has many similarities with populations known to be at risk in thermal extremes.

ABSTRACT

Preterm-born individuals are a uniquely vulnerable population. Preterm exposure to the extrauterine environment and the (mal)adaptations that occur during the transitional period can result in alterations to their macro- and micro-physiological state. The physiological adaptations that increase survival in the short term may place those born preterm on a trajectory of lifelong dysfunction and later-life decompensation. Cardiovascular compensation in children and adolescents, which masks this trajectory of dysfunction, is overcome under stress, such that the functional cardiovascular capacity is reduced and recovery impaired following physiological stress. This has implications for their response to thermal stress. As the Anthropocene introduces greater changes in our environment, thermal extremes will impact vulnerable populations as yet unidentified in the climate change context. Here, we present the hypothesis that individuals born preterm are a vulnerable population at an increased risk of cardiovascular morbidity and mortality during thermal extremes.

Mortality Risk of Hot Nights: A Nationwide Population-Based Retrospective Study in Japan

BACKGROUND

The health effects of heat are well documented; however, limited information is available regarding the health risks of hot nights. Hot nights have become more common, increasing at a faster rate than hot days, making it urgent to understand the characteristics of the hot night risk.

OBJECTIVES

We estimated the effects of hot nights on the cause- and location-specific mortality in a nationwide assessment over 43 y (1973-2015) using a unified analytical framework in the 47 prefectures of Japan.

METHODS

Hot nights were defined as days with a) minimum temperature ≥ 25 ° C (HN 25 ) and b) minimum temperature ≥ 95 th percentile (HN 95 th ) for the prefecture. We conducted a time-series analysis using a two-stage approach during the hot night occurrence season (April-November). For each prefecture, we estimated associations between hot nights and mortality controlling for potential confounders including daily mean temperature. We then used a random-effects meta-analytic model to estimate the pooled cumulative association.

RESULTS

Overall, 24,721,226 deaths were included in this study. Nationally, all-cause mortality increased by 9%-10% [HN 25 relative risk ( RR ) = 1.09 , 95% confidence interval (CI): 1.08, 1.10; HN 95 th RR = 1.10 , 95% CI: 1.09, 1.11] during hot nights in comparison with nonhot nights. All 11 cause-specific mortalities were strongly associated with hot nights, and the corresponding associations appeared to be acute and lasted a few weeks, depending on the cause of death. The strength of the association between hot nights and mortality varied among prefectures. We found a higher mortality risk from hot nights in early summer in comparison with the late summer in all regions.

CONCLUSIONS

Our findings support the evidence of mortality impacts from hot nights in excess of that explicable by daily mean temperature and have implications useful for establishing public health policy and research efforts estimating the health effects of climate change. https://doi.org/10.1289/EHP11444.

A Multi-Pollutant and Meteorological Analysis of Cardiorespiratory Mortality among the Elderly in São Paulo, Brazil-An Artificial Neural Networks Approach

Traditionally, studies that associate air pollution with health effects relate individual pollutants to outcomes such as mortality or hospital admissions. However, models capable of analyzing the effects resulting from the atmosphere mixture are demanded. In this study, multilayer perceptron neural networks were evaluated to associate PM₁₀, NO₂, and SO₂ concentrations, temperature, wind speed, and relative air humidity with cardiorespiratory mortality among the elderly in São Paulo, Brazil. Daily data from 2007 to 2019 were considered and different numbers of neurons on the hidden layer, algorithms, and a combination of activation functions were tested. The best-fitted artificial neural network (ANN) resulted in a MAPE equal to 13.46%. When individual season data were analyzed, the MAPE decreased to 11%. The most influential variables in cardiorespiratory mortality among the elderly were PM₁₀ and NO₂ concentrations. The relative humidity variable is more important during the dry season, and temperature is more important during the rainy season. The models were not subjected to the multicollinearity issue as with classical regression models. The use of ANNs to relate air quality to health outcomes is still very incipient, and this work highlights that it is a powerful tool that should be further explored.

Heatwave and urinary hospital admissions in China: Disease burden and associated economic loss, 2014 to 2019

BACKGROUND

Many studies have shown that heatwaves are associated with an increased prevalence of urinary diseases. However, few national studies have been undertaken in China, and none have considered the associated economic losses. Such information would be useful for health authorities and medical service providers to improve their policy-making and medical resource allocation decisions.

OBJECTIVES

To explore the association between heatwaves and hospital admissions for urinary diseases and assess the related medical costs and indirect economic losses in China from 2014 to 2019.

METHODS

Daily meteorological and hospital admission data from 2014 to 2019 were collected from 23 study sites with different climatic characteristics in China. We assessed the heatwave-hospitalization associations and evaluated the location-specific attributable fractions (AFs) of urinary-related hospital admissions due to heatwaves by using a time-stratified case-crossover method with a distributed lag nonlinear model. We then pooled the AFs in a meta-analysis and estimated the national excess disease burden and associated economic losses. We also performed stratified analyses by sex, age, climate zone, and urinary disease subtype.

RESULTS

A significant association between heatwaves and urinary-related hospital admissions was found with a relative risk of 1.090 (95 % confidence interval (CI): 1.050, 1.132). The pooled AF was 8.27 % (95%CI: 4.77 %, 11.63 %), indicating that heatwaves during the warm season (May to September) caused 248,364 urinary-related hospital admissions per year, with 2.42 (95%CI: 1.35, 3.45) billion CNY in economic losses, including 2.23 (95%CI: 1.29, 3.14) billion in direct losses and 0.19 (95%CI, 0.06, 0.31) billion in indirect losses, males, people aged 15-64 years, residents of temperate continental climate zones, and patients with urolithiasis were at higher risk.

CONCLUSION

Tailored community health campaigns should be developed and implemented to reduce the adverse health effects and economic losses of heatwave-related urinary diseases, especially in the context of climate change.

Community-Based Trial Educational Heat Disorder Program in Local Salons for Older Adults

We investigated whether a combined program for heat disorder prevention can improve the behaviors and knowledge of heat disorder prevention in older adults participating in salons. This non-randomized parallel-group comparison study includes 59 participants from two salons. The intervention group met on alternate weeks on a salon day to watch an educational DVD and conduct hands-on education (Wet-Bulb Globe Temperature (WBGT) measurements inside and outside the meeting place). The intervention group conducted calls every other week except salon week to prevent action for heat disorder prevention information based on a leaflet and monitored WBGT in their bedrooms daily at bedtime. We assessed changes in recognition of heat disorders and prevention behavior between baseline, one and a half months after intervention, and post-season (approximately two months after baseline), using the Wilcoxon signed rank test. Recognition of heat disorder scores and preventive behavior improved from pre- to post-season in the intervention group. It was suggested that the approach toward older adults participating in salons could improve their recognition and behavior in preventing heat disorders.

Effects of indoor summer dehumidification and winter humidification on the physiological and subjective responses of the elderly

The purpose of this study was to clarify the physiological and subjective responses of the elderly to dehumidification in a humid summer and humidification in a dry winter compared with the young. Sixteen elderly and sixteen young subjects participated in the dehumidification experiment (DE) and 13 elderly and 15 young subjects participated in the humidification experiment (HE). The air temperature in the climate chamber was set at 28 °C, and humidity was decreased from 70% relative humidity (RH) to 50% RH for 90 min in the DE. The air temperature was set at 25 °C, and the humidity was increased from 30% RH to 50% RH for 90 min in the HE. Skin temperature, body weight, transepidermal water loss (TEWL), skin hydration state, saccharin clearance time (SCT), and blinking frequency were measured during exposure; whereby we evaluated humidity sensation, thermal sensation, and thermal comfort. Dehumidification caused a significant decrease in skin temperature in both age groups owing to greater insensible perspiration. Humidification significantly shortened the SCT in both age groups. TEWL increased significantly in the DE and decreased in the HE. For the physiological responses (skin temperature, skin physiology, SCT, and blinking frequency) to dehumidification and humidification, no distinct differences between the age groups were observed. However, subjective responses suggested that the elderly were less sensitive to humidity differences than the young in both the DE and HE.

Segmental bioelectrical impedance analysis for Korean older population with cold pattern

OBJECTIVE

This study examined the association of whole-body composition and segmental bioimpedance variables with cold pattern (CP) in different sexes.

METHODS

We assigned 667 older individuals to a CP group (n = 488) and a non-CP group (n = 179) by using an eight-item self-administered questionnaire. Seven body composition variables and three pairs of segmental bioimpedance variables for the upper and lower extremities, which were obtained from a segmental multifrequency bioimpedance analyzer, were employed to investigate their association with CP. Participants' characteristics were first described. Then we compared the selected body composition and bioimpedance variables between the CP and non-CP groups. Finally, their association with CP was investigated using univariate and multivariate regression analyses. All analyses were performed separately for women and men.

RESULTS

Both women and men exhibited a comparable mean age in the CP and non-CP groups; however, women with CP had significantly lower blood pressures, whereas men with CP showed a higher proportion of osteoarthritis than those without CP. Compared with the non-CP group, individuals with CP exhibited significantly smaller body sizes indicated by shorter height and smaller weight, lower body mass index, and smaller volume-to-body surface area ratio in both sexes. After controlling for age, height, weight, and other covariates, we found significant reductions in body lean mass such as fat-free mass and body cell mass, basal metabolic rate per unit mass, total body water, and intra-to-extracellular water ratio in the CP group. With regard to segmental bioimpedance analysis, the resistance ratios and phase angles in the upper and lower extremities yield significant associations with CP incidence, as demonstrated by the odds ratio (95% confidence interval) of 1.72 (1.16-2.57), 1.69 (1.18-2.48), 0.60 (0.40-0.89), and 0.57 (0.39-0.82), respectively. However, these results did not emerge in men.

CONCLUSION

Abnormal cellular water distribution and deterioration in body cell mass and/or cell strength are associated with CP prevalence, regardless of age, height, weight. These findings are similar in the upper and lower extremities and are more pronounced in women. The abovementioned patterns may be considered effective indicators for identifying CP in the older adult population.

Multidimensional Environmental Factors and Sleep Health for Aging Adults: A Focused Narrative Review

The timing, amount, and quality of sleep are critical for an individual's health and quality of life. This paper provides a focused narrative review of the existing literature around multidimensional environments and sleep health for aging adults. Five electronic databases, Scopus, Web of Science, PubMed/Medline; EBSCOhost, PsycINFO (ProQuest), and Google Scholar yielded 54,502 total records. After removing duplicates, non-peer reviewed academic articles, and nonrelevant articles, 70 were included for review. We were able to categorize environmental factors into housing security, home environment, and neighborhood environment, and, within each environmental category, specific elements/aspects are discussed. This paper provides a comprehensive map connecting identified levels of influence (individual, home/house, and neighborhood-level) in which subfactors are listed under each level of influence/category with the related literature list. Our review highlights that multidimensional environmental factors can affect aging adults' sleep health and eventually their physical, mental, and cognitive health and that sleep disparities exist in racial minorities in socioeconomically disadvantaged communities in which cumulative environmental stressors coexist. Based on this focused narrative review on the multidimensional sleep environments for aging adults, knowledge gaps are identified, and future research directions are suggested.

Alpha-Lipoic Acid Supplementation Restores Early Age-Related Sensory and Endothelial Dysfunction in the Skin

Many changes characterize skin aging, and the resulting dysfunctions still constitute a real challenge for our society. The aim of this study was to compare the skin aging of two rat strains, Wistar and Brown Norway (BN), considered as "poorly aging" and "healthy aging" models, respectively, and to assess the effect of alpha-lipoic acid (LPA), especially on skin microcirculation. To this purpose, various skin characteristics were studied at 6, 12, and 24 months and compared to the results of LPA treatment performed at 12 or 24 months. Skin aging occurred in both strains, but we showed an early occurrence of different age-related disorders in the Wistar strain compared to BN strain, especially regarding weight gain, glycemia dysregulation, basal skin perfusion, endothelial function, and skin resistance to low pressure. LPA treatment tended to improve skin resistance to low pressure in BN but not in Wistar despite the improvement of basal skin perfusion, endothelial function, and skin sensory sensitivity. Overall, this study confirmed the healthier aging of BN compared to Wistar strain and the positive effect of LPA on both general state and skin microcirculation.

Investigating the Adaptive Thermal Comfort of the Elderly in Rural Mutual Aid Homes in Central Inner Mongolia

In the present study, questionnaires and field measurements were carried out to investigate the thermal sensation, thermal preference, and adaptive behavior of 216 elderly people living in rural mutual aid homes in central Inner Mongolia from 15 December 2020 to 31 December 2020. The main objective of this article was to understand the thermal comfort of the elderly at different ages and provide a reference for the design and construction of mutual aid homes from the perspective of adaptive thermal comfort. The obtained results showed that the average clothing thermal resistance of the elderly is 1.36 clo, and the thermal neutral temperature is 20.52 °C. Moreover, the 80% acceptable temperature range of the elderly is 15.48–25.56 °C, and the thermal expectation temperature is 21.09 °C. Then, an adaptive thermal comfort model was established for the elderly in rural mutual aid hospitals in the region. It was found that the thermal resistance, thermal neutral temperature, and thermal sensitivity of the clothing of the elderly of different ages are significantly different. The difference is especially more pronounced for the elderly over 80 years. Therefore, the differences in the thermal comfort needs of the elderly of different ages should be considered in the construction of rural mutual aid homes. This article is expected to provide a reference for the design of rural mutual aid homes and the update of heating systems.

Aging Hearts in a Hotter, More Turbulent World: The Impacts of Climate Change on the Cardiovascular Health of Older Adults

PURPOSE OF REVIEW

Climate change has manifested itself in multiple environmental hazards to human health. Older adults and those living with cardiovascular diseases are particularly susceptible to poor outcomes due to unique social, economic, and physiologic vulnerabilities. This review aims to summarize those vulnerabilities and the resultant impacts of climate-mediated disasters on the heart health of the aging population.

RECENT FINDINGS

Analyses incorporating a wide variety of environmental data sources have identified increases in cardiovascular risk factors, hospitalizations, and mortality from intensified air pollution, wildfires, heat waves, extreme weather events, rising sea levels, and pandemic disease. Older adults, especially those of low socioeconomic status or belonging to ethnic minority groups, bear a disproportionate health burden from these hazards. The worldwide trends responsible for global warming continue to worsen climate change-mediated natural disasters. As such, additional investigation will be necessary to develop personal and policy-level interventions to protect the cardiovascular wellbeing of our aging population.

Cold evoked potentials elicited by rapid cooling of the skin in young and elderly healthy individuals

Cold-evoked potentials (CEPs) constitute a novel electrophysiological tool to assess cold-specific alterations in somatosensory function. As an important step towards the clinical implementation of CEPs as a diagnostic tool, we evaluated the feasibility and reliability of CEPs in response to rapid cooling of the skin (-300 °C/s) and different stimulation sites in young and elderly healthy individuals. Time-locked electroencephalographic responses were recorded from at vertex in fifteen young (20-40 years) and sixteen elderly (50-70 years), individuals in response to 15 rapid cold stimuli (-300 °C/s) applied to the skin of the hand dorsum, palm, and foot dorsum. High CEP proportions were shown for young individuals at all sites (hand dorsum/palm: 100% and foot: 79%) and elderly individuals after stimulation of the hand dorsum (81%) and palm (63%), but not the foot (44%). Depending on the age group and stimulation site, test-retest reliability was "poor" to "substantial" for N2P2 amplitudes and N2 latencies. Rapid cooling of the skin enables the recording of reliable CEPs in young individuals. In elderly individuals, CEP recordings were only robust after stimulation of the hand, but particularly challenging after stimulation of the foot. Further improvements in stimulation paradigms are warranted to introduce CEPs for clinical diagnostics.

Thermal sensation index for elderly people living in Brazil

With the aging of the human body, some physiological changes occur, compromising thermoregulatory mechanisms, negatively influencing the individual's thermal sensation. Given this fact, the present study aimed to build a predictive model to determine the thermal sensation index for elderly people (TSIEP) in a hot climate region, considering their sensitivity in the perception of climate change in the city of Campina Grande, in the semi-arid region of Paraíba/Brazil. For this purpose, an observational study was carried out from April to December 2016 with elderly people inside their homes. The responses of the sample units (elderly people) to the categories of thermal sensation (hot, comfortable, and cold) were transformed into probit estimates, and, using the multivariate modeling statistical technique (canonical correlation), the TSIEP was determined. Finally, TSIEP showed that the thermal sensation of elderly people residing in Campina Grande tends to be more sensitive to cold and less sensitive to heat.

A Case Study of a Nursing Home in Nagano, Japan: Field Survey on Thermal Comfort and Building Energy Simulation for Future Climate Change

With an increase in the aging population in many countries worldwide, much attention is being paid to the study of thermal comfort for the elderly. Because the elderly spend most of their time indoors, the demand for air conditioning is expected to increase, and it is important to study the thermal comfort of the elderly and appropriate operation plans for air conditioning. In this study, we conducted a field survey of thermal comfort and building energy simulation for an air-conditioned nursing home in Nagano, Japan. The field survey was conducted between June 2020 and June 2021. Over 80% of the subjects were satisfied with the indoor thermal environment. The thermal neutral temperature of the elderly was 25.9 °C in summer and 23.8 °C in winter. Future weather data was used to predict the future heating and cooling loads of the nursing home. The results showed that the total heat load may not change significantly, as the decrease in heating load compensates for the increase in cooling load. This study will serve as a useful reference for a wide range of stakeholders, including managers and designers of nursing homes.

The Thermal Environment of Housing and Its Implications for the Health of Older People in South Australia: A Mixed-Methods Study

Older people are often over-represented in morbidity and mortality statistics associated with hot and cold weather, despite remaining mostly indoors. The study “Improving thermal environment of housing for older Australians” focused on assessing the relationships between the indoor environment, building characteristics, thermal comfort and perceived health/wellbeing of older South Australians over a study period that included the warmest summer on record. Our findings showed that indoor temperatures in some of the houses reached above 35 °C. With concerns about energy costs, occupants often use adaptive behaviours to achieve thermal comfort instead of using cooling (or heating), although feeling less satisfied with the thermal environment and perceiving health/wellbeing to worsen at above 28 °C (and below 15 °C). Symptoms experienced during hot weather included tiredness, shortness of breath, sleeplessness and dizziness, with coughs and colds, painful joints, shortness of breath and influenza experienced during cold weather. To express the influence of temperature and humidity on perceived health/wellbeing, a Temperature Humidity Health Index (THHI) was developed for this cohort. A health/wellbeing perception of “very good” is achieved between an 18.4 °C and 24.3 °C indoor operative temperature and a 55% relative humidity. The evidence from this research is used to inform guidelines about maintaining home environments to be conducive to the health/wellbeing of older people.

Dysfunctional TRPM8 signalling in the vascular response to environmental cold in ageing

Ageing is associated with increased vulnerability to environmental cold exposure. Previously, we identified the role of the cold-sensitive transient receptor potential (TRP) A1, M8 receptors as vascular cold sensors in mouse skin. We hypothesised that this dynamic cold-sensor system may become dysfunctional in ageing. We show that behavioural and vascular responses to skin local environmental cooling are impaired with even moderate ageing, with reduced TRPM8 gene/protein expression especially. Pharmacological blockade of the residual TRPA1/TRPM8 component substantially diminished the response in aged, compared with young mice. This implies the reliance of the already reduced cold-induced vascular response in ageing mice on remaining TRP receptor activity. Moreover, sympathetic-induced vasoconstriction was reduced with downregulation of the α_2c adrenoceptor expression in ageing. The cold-induced vascular response is important for sensing cold and retaining body heat and health. These findings reveal that cold sensors, essential for this neurovascular pathway, decline as ageing onsets.

Ageing reduces skin wetness sensitivity across the body

NEW FINDINGS

What is the central question of this study? Ageing impairs the skin's thermal and tactile sensitivity: does ageing also induce loss of skin wetness sensitivity? What is the main finding and its importance? Older adults show an average 15% loss of skin wetness sensitivity, with this sensory deficit being mediated by a combination of reductions in skin's tactile sensing and hydration status. These findings increase knowledge of wetness sensing mechanisms across the lifespan.

ABSTRACT

Humans use sensory integration mechanisms to sense skin wetness based on thermal and mechanical cues. Ageing impairs the skin's thermal and tactile sensitivity, yet we lack evidence on whether wetness sensing also changes with ageing. We mapped local skin wetness and temperature sensitivity in response to cold-, neutral- and warm-wet stimuli applied to the forehead, neck, lower back, dorsal foot, index finger and thumb, in 10 Younger (22.4 ± 1.1 years) and 10 Older (58.2 ± 5.1 years) males. We measured local skin temperature and conductance (i.e., a marker of hydration status) at the tested sites, to establish the role of skin's thermal and mechanical parameters in ageing-induced changes in wetness sensing. Irrespective of body site, Older reported overall lower wetness perceptions than Younger across all wet-stimulus temperatures (mean difference: -14.6 mm; 95% CI: -4.3, -24.9; P = 0.008; ∼15% difference). When considering regional wetness sensitivity, the effect of ageing was more pronounced in response to the cold-wet stimulus over the lover back (mean difference Older vs. Younger: -36.8 mm; 95% CI: -68.4, -5.2; P = 0.014; ∼37% difference) and dorsal foot (mean difference: -37.1 mm; 95% CI: -68.7, -5.5; P = 0.013; ∼37% difference). We found no differences between age groups on overall thermal sensations (P = 0.744) nor local skin temperature (P = 0.372); however, we found that Older presented overall lower skin conductance than Younger (mean difference: -1.56 μS; 95% CI: -0.49, -2.62; P = 0.005), which corresponded to an ∼78% reduction in skin hydration. We conclude that skin wetness sensing decreases with ageing primarily due to age-induced changes in skin mechanics and tactile sensitivity.

The role of outdoor microclimatic features at long-term care facilities in advancing the health of its residents: An integrative review and future strategies

Projections show that Earth's climate will continue to warm concurrent with increases in the percentage of the world's elderly population. With an understanding that the body's resilience to the heat degrades as it ages, these coupled phenomena point to serious concerns of heat-related mortality in growing elderly populations. As many of the people in this age cohort choose to live in managed long-term care facilities, it's imperative that outdoor spaces of these communities be made thermally comfortable so that connections with nature and the promotion of non-sedentary activities are maintained. Studies have shown that simply being outside has a positive impact on a broad range of the psychosocial well-being of older adults. However, these spaces must be designed to afford accessibility, safety, and aesthetically pleasing experiences so that they are taken full advantage of. Here, we employ an integrative review to link ideas from the disciplines of climate science, health and physiology, and landscape architecture to explain the connections between heat, increased morbidity and mortality in aging adults, existing gaps in thermal comfort models, and key strategies in the development of useable, comfortable outdoor spaces for older adults. Integrative reviews allow for new frameworks or perspectives on a subject to be introduced. Uncovering the synergy of these three knowledge bases can contribute to guiding microclimatic research, design practitioners, and care providers as they seek safe, comfortable and inviting outdoor spaces for aging adults.

Attributable risks of hospitalizations for urologic diseases due to heat exposure in Queensland, Australia, 1995-2016

BACKGROUND

Heat exposure is a risk factor for urologic diseases. However, there are limited existing studies that have examined the relationship between high temperatures and urologic disease. The aim of this study was to examine the associations between heat exposure and hospitalizations for urologic diseases in Queensland, Australia, during the hot seasons of 1995-2016 and to quantify the attributable risks.

METHODS

We obtained 238 427 hospitalized cases with urologic diseases from Queensland Health between 1 December 1995 and 31 December 2016. Meteorological data were collected from the Scientific Information for Land Owners-a publicly accessible database of Australian climate data that provides daily data sets for a range of climate variables. A time-stratified, case-crossover design fitted with the conditional quasi-Poisson regression model was used to estimate the associations between temperature and hospitalizations for urologic diseases at the postcode level during each hot season (December-March). Attributable rates of hospitalizations for urologic disease due to heat exposure were calculated. Stratified analyses were performed by age, sex, climate zone, socio-economic factors and cause-specific urologic diseases.

RESULTS

We found that a 1°C increase in temperature was associated with a 3.3% [95% confidence interval (CI): 2.9%, 3.7%] increase in hospitalization for the selected urologic diseases during the hot season. Hospitalizations for renal failure showed the strongest increase 5.88% (95% CI: 5.25%, 6.51%) among the specific causes of hospital admissions considered. Males and the elderly (≥60 years old) showed stronger associations with heat exposure than females and younger groups. The sex- and age-specific associations with heat exposure were similar across specific causes of urologic diseases. Overall, nearly one-fifth of hospitalizations for urologic diseases were attributable to heat exposure in Queensland.

CONCLUSIONS

Heat exposure is associated with increased hospitalizations for urologic disease in Queensland during the hot season. This finding reinforces the pressing need for dedicated public health-promotion campaigns that target susceptible populations, especially for those more predisposed to renal failure. Given that short-term climate projections identify an increase in the frequency, duration and intensity of heatwaves, this public health advisory will be of increasing urgency in coming years.

Age Differences in Multimodal Quantitative Sensory Testing and Associations With Brain Volume

BACKGROUND AND OBJECTIVES

Somatosensory function is critical for successful aging. Prior studies have shown declines in somatosensory function with age; however, this may be affected by testing site, modality, and biobehavioral factors. While somatosensory function declines are associated with peripheral nervous system degradation, little is known regarding correlates with the central nervous system and brain structure in particular. The objectives of this study were to examine age-related declines in somatosensory function using innocuous and noxious stimuli, across 2 anatomical testing sites, with considerations for affect and cognitive function, and associations between somatosensory function and brain structure in older adults.

RESEARCH DESIGN AND METHODS

A cross-sectional analysis included 84 "younger" (n = 22, age range: 19-24 years) and "older" (n = 62, age range: 60-94 years) healthy adults who participated in the Neuromodulatory Examination of Pain and Mobility Across the Lifespan study. Participants were assessed on measures of somatosensory function (quantitative sensory testing), at 2 sites (metatarsal and thenar) using standardized procedures, and completed cognitive and psychological function measures and structural magnetic resonance imaging.

RESULTS

Significant age × test site interaction effects were observed for warmth detection (p = .018,η p 2 = 0.10) and heat pain thresholds (p = .014,η p 2 = 0.12). Main age effects were observed for mechanical, vibratory, cold, and warmth detection thresholds (ps < .05), with older adults displaying a loss of sensory function. Significant associations between somatosensory function and brain gray matter structure emerged in the right occipital region, the right temporal region, and the left pericallosum.

DISCUSSION AND IMPLICATIONS

Our findings indicate healthy older adults display alterations in sensory responses to innocuous and noxious stimuli compared to younger adults and, furthermore, these alterations are uniquely affected by anatomical site. These findings suggest a nonuniform decline in somatosensation in older adults, which may represent peripheral and central nervous system alterations part of aging processes.

Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies

A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances, and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat by examining the benefits of heat acclimation, cooling strategies, and hyperhydration. Finally, contemporary controversies are summarized and future research directions are provided.

[A delayed diagnosis of thyroid storm in an elderly patient: A case report]

A 70-year-old woman was hospitalized for diarrhea, vomiting, loss of appetite, fatigue, and dyspnea on exertion for the past 3 weeks and treated with intravenous fluid for dehydration. She was receiving prednisolone for polymyositis. She did not have a history of thyroid disease. On day 4 of hospitalization, the patient was diagnosed with congestive heart failure and tachycardiac atrial fibrillation, and treatment with a diuretic agent was initiated. On day 7 of hospitalization, a clinical laboratory evaluation revealed that the level of free thyroxine was 9.95 ng/dL, free triiodothyronine was >30 pg/mL, and thyroid-stimulating hormone was <0.01 μU/mL, and the patient was initially diagnosed with thyrotoxicosis because of Graves' disease. She showed restlessness and had a fever of 39 °C, tachycardia of ≥140 beats/min, pulmonary edema, and frequent diarrhea, all of which were consistent with the symptoms of thyroid storm. Her general condition gradually improved with comprehensive treatment of thyroid storm comprising thiamazole, potassium iodide, hydrocortisone, and landiolol. A reassessment revealed that the patient had already had thyrotoxicosis and thyroid storm on admission. Thyroid storm is a potentially fatal disease that must be urgently addressed; however, its symptoms are difficult to distinguish from those caused by other diseases. Furthermore, elderly individuals may not exhibit typical symptoms of thyroid storm, so the diagnosis is difficult. In this case, the diagnosis was delayed because of the absence of typical symptoms of thyroid storm and the influence of a pre-existing medical condition and medication.

Can within-subject comparisons of thermal thresholds be used for diagnostic purposes?

OBJECTIVE

Quantitative thermal testing (QTT) is a psychophysical assessment method of small nerve fibers that relies on reference material to assess function. Normal limits for within-subject comparisons of thermal thresholds are scarce, and their association with age, height and sex is not fully elucidated. The aim of this study was to investigate the normal limits for distal-proximal- and contralateral homologous comparisons of thermal thresholds with QTT, and their association with age, sex or height.

METHODS

Fifty healthy volunteers ages 20-79 participated in the experiment. Cold detection thresholds (CDT), warm detection thresholds (WDT), heat pain thresholds (HPT), and cold pain thresholds (CPT) were measured bilaterally at the thenar eminence, anterior thigh, distal medial leg and foot dorsum. Sample normal limits were calculated as (mean) ± 2 SD.

RESULTS

Forty-eight subjects were included in the analysis. CPT was excluded from all analyses due to a large floor-effect. Sample normal limits for side-differences ranged from 1.8 to 7.2 °C for CDT, 2.4-6.8 °C for WDT and 3.2-4.0 °C for HPT, depending on anatomical site. For distal-proximal comparisons, sample normal limits ranged from 4.0 to 8.7 °C for CDT, 6.0-14.0 °C for WDT and 4.2-9.0 °C for HPT, depending on the pairs compared. Age was associated with side-differences for CDT in the thenar eminences (p < 0.001) and distal medial legs (p < 0.002), and with 11 of 18 distal-proximal comparisons (p < 0.01).

CONCLUSIONS

The normal limits for distal-proximal- and contralateral homologous thermal thresholds were wide, and thus of limited use in a clinical setting, although the reported values may be somewhat inflated by low sample-size and consequent age-pooling. Age, but not sex or height, was associated with contralateral differences in CDT in the thenar eminences and distal medial legs, and with most distal-proximal differences.

SIGNIFICANCE

Due to wide normal limits, we advise caution when utilizing relative comparisons of thermal thresholds for diagnostic purposes.

Bilateral skin temperature drop and warm sensibility decrease following modulation of body part ownership through mirror-box illusion

The implicit and explicit awareness of owning a body and its parts is a constant accompaniment in our everyday life and our interaction with the outside world. The way in which we build and maintain a coherent sense of body ownership is not fully understood. It has been postulated that the integration between exteroceptive, interoceptive, and proprioceptive signals may play a fundamental role in the sense of body ownership. For instance, studies on healthy subjects and brain-damaged patients have suggested that alterations in the sense of body ownership are coupled with autonomic signal changes, such as thermoregulatory reactions. However, the available evidence is conflicting, possibly due to shortcomings in the experimental paradigm that previous studies have adopted. In this study, we explore the relationship between body ownership, thermoregulation, and thermal sensitivity through a novel application of the mirror-box illusion paradigm, overcoming some of the limitations of previous studies. We find a bilateral decrease in hand skin temperature, together with reduced thermal sensitivity for warm thermal stimuli following the induction of the illusion of ownership towards the participant's reflected hand. These findings demonstrate the importance of the orchestration of exteroceptive (e.g., visual), autonomic (e.g., body temperature) and proprioceptive (e.g., position and movement of the body) signals in maintaining a coherent sense of body ownership.

Physiological factors characterizing heat-vulnerable older adults: A narrative review

More frequent and intense periods of extreme heat (heatwaves) represent the most direct challenge to human health posed by climate change. Older adults are particularly vulnerable, especially those with common age-associated chronic health conditions (e.g., cardiovascular disease, hypertension, obesity, type 2 diabetes, chronic kidney disease). In parallel, the global population is aging and age-associated disease rates are on the rise. Impairments in the physiological responses tasked with maintaining homeostasis during heat exposure have long been thought to contribute to increased risk of health disorders in older adults during heatwaves. As such, a comprehensive overview of the provisional links between age-related physiological dysfunction and elevated risk of heat-related injury in older adults would be of great value to healthcare officials and policy makers concerned with protecting heat-vulnerable sectors of the population from the adverse health impacts of heatwaves. In this narrative review, we therefore summarize our current understanding of the physiological mechanisms by which aging impairs the regulation of body temperature, hemodynamic stability and hydration status. We then examine how these impairments may contribute to acute pathophysiological events common during heatwaves (e.g., heatstroke, major adverse cardiovascular events, acute kidney injury) and discuss how age-associated chronic health conditions may exacerbate those impairments. Finally, we briefly consider the importance of physiological research in the development of climate-health programs aimed at protecting heat-vulnerable individuals.

Model-based approach for analyzing prevalence of nuclear cataracts in elderly residents

Recent epidemiological studies have hypothesized that the prevalence of cortical cataracts is closely related to ultraviolet radiation. However, the prevalence of nuclear cataracts is higher in elderly people in tropical areas than in temperate areas. The dominant factors inducing nuclear cataracts have been widely debated. In this study, the temperature increase in the lens due to exposure to ambient conditions was computationally quantified in subjects of 50-60 years of age in tropical and temperate areas, accounting for differences in thermoregulation. A thermoregulatory response model was extended to consider elderly people in tropical areas. The time course of lens temperature for different weather conditions in five cities in Asia was computed. The temperature was higher around the mid and posterior part of the lens, which coincides with the position of the nuclear cataract. The duration of higher temperatures in the lens varied, although the daily maximum temperatures were comparable. A strong correlation (adjusted R² > 0.85) was observed between the prevalence of nuclear cataract and the computed cumulative thermal dose in the lens. We propose the use of a cumulative thermal dose to assess the prevalence of nuclear cataracts. Cumulative wet-bulb globe temperature, a new metric computed from weather data, would be useful for practical assessment in different cities.

Heat Wave and Elderly Mortality: Historical Analysis and Future Projection for Metropolitan Region of São Paulo, Brazil

The Metropolitan Region of Sao Paulo (MRSP) is one of the main regions of Brazil that in recent years has shown an increase in the number of days with heat waves, mainly affecting the health of the most sensitive populations, such as the elderly. In this study, we identified the heat waves in the MRSP using three different definitions regarding the maximum daily temperature threshold. To analyze the impact of heat waves on elderly mortality, we used distributed lag nonlinear models (dlnm) and we quantified the heat wave-related excess mortality of elderly people from 1985 to 2005 and made projections for the near future (2030 to 2050) and the distant future (2079–2099) under the climate change scenarios RCP4.5 and RCP8.5 (RCP: Representative Concentration Paths). An important aspect of this research is that for the projections we take into account two assumptions: non-adaptation and adaptation to the future climate. Our projections show that the heat wave-related excess of elderly mortality will increase in the future, being highest when we consider no adaptation, mainly from cardiovascular diseases in women (up to 587 deaths per 100,000 inhabitants per year). This study can be used for public policies to implement preventive and adaptive measures in the MRSP.

Effects of cold exposure discontinuation on finger cold-induced vasodilation of older retired Korean female divers 'Haenyeos'

The purpose of the present study was to investigate the effects of cold exposure discontinuation on local cold tolerance of older retired female haenyeos in Korea. A total of 30 older women participated in this study: older retired haenyeos (89 ± 4 y in age, N = 10), active haenyeos (current divers) (75 ± 4 y, N = 10), and age-matched non-divers (75 ± 6 y, N = 10). Our criterion for local cold tolerance was cold-induced vasodilation (CIVD) of the finger. Active haenyeos showed greater local cold tolerance in terms of higher minimum temperature of the left finger during immersion and recovery than the other two groups (P < 0.05). Furthermore, active haenyeos showed higher skin temperatures of the right finger and left foot as well (P < 0.05). Older retired haenyeos displayed the second best minimum finger temperature both during immersion and during recovery (15 min and 20 min), whereas their local cold tolerance was evaluated as inferior to active haenyeos and the age-matched non-divers in CIVD frequency, finger pain sensation, thermal comfort, and finger temperature during the earlier period of recovery (5 min and 10 min). These results suggested that older retired haenyeos' cold tolerance in their extremities disappeared in terms of finger temperature in their initial recovery periods, but that they might still retain cold adaptation in terms of minimum finger temperature or later recovery responses, even though the attributes were not marked as much as those of active haenyeos.

Characterization of pain syndromes in patients with neuromyelitis optica

BACKGROUND

Pain is common and refractory in spinal cord injury (SCI). Currently, most studies evaluated pain in male-predominant traumatic-SCI. Also, concomitant secondary pain syndromes and its temporal evolution were seldom reported.

METHODS

We aimed to prospectively describe the main and secondary pain and its associated factors in inflammatory-SCI evaluating neuromyelitis optica (NMO) patients. In-remission NMO patients underwent neurological, imaging and autoantibody evaluations. Questionnaires detailing main and secondary pains, functional state, mood, catastrophizing, quality of life (QoL) and "non-motor symptoms" were used at two time points.

RESULTS

Pain was present in 53 (73.6%) of the 72 patients included. At-level neuropathic pain was the most common main pain syndrome, affecting 32 subjects (60.4% of those with pain). Over 70% (n = 38) of this cohort reported two pain syndromes. Those without pain were significantly younger (26.1 ± 12.7 y.o. in those without pain and 40.1 ± 12.5, 37.2 ± 11.4 y.o. in those whose main pain was neuropathic and non-neuropathic, respectively, p = .001), and no differences in the inflammatory status were observed between groups. On follow-up, one-fifth (n = 11) had a different main pain syndrome from the first visit. Pain impacted QoL as much as disability and motor strength.

CONCLUSION

Pain is a prevalent and disabling non-motor symptom in NMO-SCI. Most patients experience more than one pain syndrome which can change in time even in the absence of clinical relapse. Age of the inflammatory-SCI was a major determinant of pain. Acknowledging temporal changes and multiplicity of pain syndromes in NMO-SCI may give insights into more precise designs of clinical trials and general management of pain in SCI.

SIGNIFICANCE

In this longitudinal study with NMO-related SCI, pain affected almost three-quarters of patients with NMO. Over 70% have more than one pain syndrome and at-level neuropathic pain is the most common type of pain syndrome. Patients without pain were significantly younger but had the same burden of inflammatory lesions than those with pain. During follow-up, up to one fifth of patients presented with changes in the main pain syndromes, which can occur even in the absence of clinical activity of the inflammatory disease. In this cohort, Pain affected quality of life as much as disability or motor strength.

Quantitative Sensory Testing (QST) in Drug-Naïve Patients with Parkinson's Disease

BACKGROUND

Pain is highly prevalent in patients with Parkinson's disease (PD), but underlying pathophysiological mechanisms are largely unclear. Alterations in somatosensory processing might contribute to sensory abnormalities in PD.

OBJECTIVE

This study investigated sensory processing in PD patients.

METHODS

We used the standardized "Quantitative Sensory Testing" (QST) protocol (German Research Network on Neuropathic Pain) to investigate 13 somatosensory parameters in 19 PD patients naïve to dopaminergic medication and 19 healthy controls matched for age, gender, and handedness. We tested for differences in sensory parameters between i) drug-naïve PD patients and healthy controls, ii) patients' more and less affected body side, and iii) for an association of somatosensory parameters with disease-specific factors.

RESULTS

We did not observe any significant group differences in somatosensory parameters between PD patients and healthy subjects. In PD patients, QST mean z-scores did not differ between the predominantly and the less affected body side, PD patients with and without PD-specific chronic pain or between different PD subtypes. Age, but not PD disease severity, was associated with a greater loss of function in thermal and mechanical detection thresholds.

CONCLUSIONS

Somatosensory processing, as assessed with the well-established QST protocol, was normal in drug-naïve PD patients. Thus, somatosensory abnormalities previously reported in medicated PD patients might rather be a result of dopaminergic medication, or may occur later in the course of the disease or with increasing age.

Personal Cold Protection Behaviour and Its Associated Factors in 2016/17 Cold Days in Hong Kong: A Two-Year Cohort Telephone Survey Study

Background: Despite larger health burdens attributed to cold than heat, few studies have examined personal cold protection behaviours (PCPB). This study examined PCPB during cold waves and identified the associated factors in a subtropical city for those without central heating system. Methods: A cohort telephone survey was conducted in Hong Kong during a colder cold wave (2016) and a warmer cold wave (2017) among adults (≥15). Socio-demographic information, risk perception, self-reported adverse health effects and patterns of PCPB during cold waves were collected. Associated factors of PCPB in 2017 were identified using multiple logistic regression. Results: The cohort included 429 subjects. PCPB uptake rates were higher during the colder cold wave (p < 0.0005) except for ensuring indoor ventilation. Of the vulnerable groups, 63.7% had low self-perceived health risks. High risk perception, experience of adverse health effects during the 2016 cold wave, females and older groups were positive associated factors of PCPB in 2017 (p < 0.05). Conclusions: PCPB changed with self-risk perception. However vulnerable groups commonly underestimated their own risk. Indoor ventilation may be a concern during cold days in settings that are less prepared for cold weather. Targeted awareness-raising promotion for vulnerable groups and practical strategies for ensuring indoor ventilation are needed.

Developing Guidelines for Thermal Comfort and Energy Saving during Hot Season of Multipurpose Senior Centers in Thailand

In Thailand, many government buildings and facilities are adapted to serve as Multipurpose Senior Centers (MSCs). However, most of them have been used without taking into account of thermal comfort of occupants. The present research aimed to develop guidelines for improving suitable indoor environment for the Thai elderly in hot season and analyze energy use of the 3 case-study MSCs. Both field study and climate-controlled chamber study were conducted. The obtained data were analyzed to develop the equation for predicting the thermal sensation, which would be inputted in the scSTREAM program for analysis purposes. The energy use was evaluated using the DOE-2 program. The results suggested that during 8:00 a.m.–12:00 p.m., natural ventilation should be used together with orbit fans to produce an actual air velocity of 0.64–0.73 m/s. From 12:00 p.m. to 4:00 p.m., air conditioners should set at 26.00–26.50 °C with an actual air velocity of 0.06–0.22 m/s. The results also showed that the developed guidelines could improve the level of thermal comfort from “slightly cool” to “neutral” and reduce energy use in hot season by 16.56% due to the reduction of cooling load and fan operation of air conditioning systems. Moreover, energy consumption in MSCs are also affected by the building parameters. These findings can be applied as guidelines for improving a large number of MSCs in Thailand.

Oral L-Tyrosine Supplementation Improves Core Temperature Maintenance in Older Adults

INTRODUCTION

During cold exposure, an increase in sympathetic nerve activity evokes vasoconstriction (VC) of cutaneous vessels to minimize heat loss. In older adults, this reflex VC response is impaired thereby increasing their susceptibility to excess heat loss and hypothermia. Because L-tyrosine, the amino acid substrate necessary for catecholamine production, has been shown to augment reflex VC in age skin, we hypothesize that oral ingestion of L-tyrosine will attenuate the decline in core temperature (Tc) during whole-body cooling in older adults.

METHODS

In a randomized, double-blind design, nine young (25 ± 3 yr) and nine older (72 ± 8 yr) participants ingested either 150 mg·kg of L-tyrosine or placebo before commencing 90 min of whole-body cooling to decrease skin temperature to approximately 29.5°C. Esophageal temperature and forearm laser Doppler flux (LDF) were measured continuously throughout the protocol to provide an index of Tc and skin blood flow, respectively. The change in esophageal temperature (ΔTES) was the difference in temperature at the end of cooling subtracted from baseline. Cutaneous vascular conductance (CVC) was calculated as CVC = LDF/mean arterial pressure and expressed as a percent change from baseline (%ΔCVCBASELINE).

RESULTS

Oral tyrosine ingestion augmented the cutaneous VC response to cooling in older adults (placebo, 14.4 ± 2.0; tyrosine, 32.7% ± 1.7% ΔCVCBASELINE; P < 0.05). Additionally, tyrosine improved Tc maintenance throughout cooling in older adults (placebo, -0.29 ± 0.07; tyrosine, -0.07 ± 0.07 ΔTES; P < 0.05). Both the cutaneous VC and Tc during cooling were similar between young and older adults supplemented with tyrosine (P > 0.05).

CONCLUSIONS

These results indicate that L-tyrosine supplementation improves Tc maintenance in response to acute cold exposure in an older population.

Quantitative sensory testing to evaluate and compare the results after epidural injection and simple discectomy, in patients with radiculopathy secondary to lumbar disc herniation

The objective assessment of the radiculopathy secondary to lumbar disc herniation is essential to optimize treatment. The quantitative sensory test (QST) is a useful tool to evaluate somatosensory nerves. The aim of our study is quantifying by QST the alterations of patients treated by epidural injections (EI) or surgical lumbar decompression (LD). A prospective, cohort study has done in Hospital Universitario Rio Hortega, Valladolid, Spain, between January 2014 and December 2016.The study includes 74 patients (40 men) who underwent EI (50) or LD (24) with lumbar disc herniation and treated by EI or LD. Participants underwent a brief battery of QST at baseline and after 1, 3 and 6 months of follow-up. QST threshold were measured in three series of five warm and cold stimuli (cold detection threshold, warm detection threshold, cold pain threshold, heat pain threshold) bilateral. Additionally, pain assessment (Visual Analogue Scale) and neurological examination was performed. Thermal thresholds were analysed and compared. In the EI group, warm detection threshold (WDT) measurements were significantly lower after 3 and 6 months of follow-up (40.44 ± 3.42°C vs. 38.30 ± 3.73°C and 37.48 ± 4.58°C respectively, p = 0.031 and p = 0.043). LD group showed lower WDT measurements at 1, 3 and 6 months of follow up (40.20 ± 2.97°C vs., 37.98 ± 2.04°C, 37.43 ± 3.80°C and 36.55 ± 2.77°C respectively, p = 0.049, p = 0.032 and p = 0.024) and lower heat pain threshold (HPT) levels after 3 and 6 months of follow-up (48.75 ± 1.37°C vs. 43.26 ± 0.60°C and 42.06 ± 1.37°C respectively, p = 0.037 and p = 0.021). QST explorations were compared between both groups. At 1-month follow-up only the WDT parameter was different, higher in EI group (40.98 ± 4.04°C vs. 37.98 ± 2.04°C, p = 0.043). There were no differences in any parameter measured by QST after 3 and 6-months follow-up between both groups. Epidural injection should be considered the first-step of treatment.