Heat Stroke Research Articles

Impact of the Estrous Cycle on Loss of Consciousness and Survival in Exertional Heat Stroke in Mice.

Exertional heat stroke (EHS) is the most severe manifestation of heat-related illness. We previously observed, in a mouse model of EHS, that the time to loss of consciousness (LOC) was longer in females compared to males. Ovariectomy abolished this sex difference and decreased the variability in time to reach LOC in our model. Here, we tested the hypothesis that the estrous cycle (EC) phase, the rodent equivalent of the menstrual cycle in humans, would influence the time to LOC in our mouse EHS model. Adult C57BL/6 female mice were implanted with telemetry sensors to measure core temperature (TCORE). Following familiarization and cytological determination of the EC, mice exercised in a forced wheel running device inside an environmental chamber set at 37.5 °C and 40% relative humidity until reaching LOC. Estrus (E) was identified by the predominant presence of cornified epithelial cells, while Diestrus (D) was identified by predominant presence of leukocytes. In comparison with mice in E group (n = 44), mice in D (n = 30) reached LOC ~18% faster (D: 169.5 ± 42.8 min; E: 192.9 ± 36.1 min; p = 0.01), despite a lower maximal running speed (Smax; E: 7.4 ± 1.1 m/min; D: 6.6 ± 1.2 m/min, p = 0.004). However, mice in E mice demonstrated a higher mortality rate post-EHS compared to mice in D. The EC influences mortality and the tolerance to EHS in mice.

Heat stroke-induced hepatic lipid dysregulation: histological and lipidomic insights.

Global warming has increased summer temperatures, leading to a rise in heat stroke-related deaths in Japan. Heat stroke disrupts the body's adaptation to high temperatures, often resulting in severe complications, including liver damage and even death. However, despite the increasing incidence, pathological autopsies remain rare, and the histological changes associated with heat stroke are poorly understood. In this study, we investigated the pathogenesis of heat stroke using a mouse model. Mice were exposed to 45°C for 30min and dissected immediately or 24, 48, and 72h post-exposure. Histological analysis revealed significant lipid accumulation in hepatocytes surrounding the central vein at 24, 48, and 72h. At 24h, hepatocytes also exhibited features of early degeneration, including cytoplasmic lysis and chromatin condensation. Lipidomics analysis of liver tissue collected 24h post-exposure demonstrated a marked increase in 27-hydroxycholesterol levels. These results indicate that heat stress rapidly disrupts hepatic lipid homeostasis, causing cellular damage and metabolic remodeling. The observed lipid accumulation, including elevated 27-hydroxycholesterol, may play dual roles in mediating inflammation and serving as a protective response. Our findings provide new insight into the pathogenesis of heat stroke-induced liver injury and suggest potential molecular targets for early diagnosis and intervention.

The Physiology Behind the Epidemiology of Heat-Related Health Impacts.

A direct consequence of climate change is the intensification of hot weather and extreme heat events that are epidemiologically associated with a greater risk of heat-related illnesses and other adverse health outcomes, often resulting in subsequent hospital admissions and mortality. The health risks associated with hot weather directly arise from the body's physiological responses (i.e., heat strain) to heat exposure. The magnitude of heat strain experienced, and the extent of heat strain required to cause an adverse health outcome can be modulated by personal characteristics and the adoption of protective behaviors. This review presents the pathophysiological mechanisms responsible for the epidemiological association between heat exposure and a greater risk of heat illnesses (e.g., heat exhaustion, heatstroke), adverse cardiovascular events, and acute kidney injury or failure. These mechanisms are framed within the larger context that defines heat-related health risks, and we provide examples and perspectives of how physiologists are uniquely positioned to contribute to risk-reduction and adaptation efforts to protect humans against the adverse health impacts of heat, while maintaining optimum well-being and performance.

Therapeutic potential of butyrate against heat Stress-Induced intestinal damage, systemic inflammation, and multiple organ Dysfunction: Insights from in vitro and in vivo experiments.

Therapeutic potential of butyrate against heat Stress-Induced intestinal damage, systemic inflammation, and multiple organ Dysfunction: Insights from in vitro and in vivo experiments.

Pathogenesis and therapeutic strategy of heat stroke-induced acute kidney injury.

Pathogenesis and therapeutic strategy of heat stroke-induced acute kidney injury.

Squash in Los Angeles: Heat Strain and Performance Considerations at the 2028 Olympic Games.

The Los Angeles 2028 Olympics will mark the debut of squash, a high-intensity sport characterized by repeated efforts, posing potential thermoregulatory challenges. The demanding nature of squash results in substantial metabolic heat production, with consequential heat strain exacerbated by the indoor environment of squash courts, where low to moderate evaporative potential limits effective cooling. Players often experience increased body-heat storage and thermal strain, with muscle cramps (an early warning sign of more severe heat-related illnesses) commonly observed during tournaments. Despite these challenges, there are limited data on the thermoregulatory responses of elite squash players during match play. We discuss the thermoregulatory challenges faced by squash players and highlight key areas for research. Additionally, practical guidelines are provided for practitioners preparing squash players for the Los Angeles 2028 Olympics. Preliminary findings from international squash tournaments reveal that elite players endure significant physiological strain, with core temperatures rising to 39.0 °C to 40.1 °C, despite matches being played in mild wet-bulb globe temperatures of 19.4 °C (0.9 °C). Sustained heart rates exceeding 90% of maximal heart rate further compound this thermal strain. However, research on how thermal strain affects squash-specific fitness, recovery, and stroke mechanics are lacking. Such information is crucial for evaluating the need and effectiveness of tailored mitigation strategies such as heat training/exposures and precooling and midcooling during warm-up and match play. Systematic research into the thermal demands of squash and their impact on fitness and skills is needed. These insights can inform evidence-based strategies to safeguard athlete well-being and optimize performance at Los Angeles 2028.

Qingshu Yiqi decoction ameliorates exertional heat stroke-induced intestinal barrier injury via NF-κB/MLC pathway and gut microbiota.

Qingshu Yiqi decoction ameliorates exertional heat stroke-induced intestinal barrier injury via NF-κB/MLC pathway and gut microbiota.

Night for Day

ABSTRACT Dystopian frameworks portend the future. With climatic upheavals increasing, dystopia is now. Because of escalating urban heat and heat-related illness and death, this essay speculates a future that switches daily activities into the coolness of night. A utopian/Noctopian vision is posited with community-engaged design combined with technologically enabled, adaptive lighting. For example, in Noctopia, the library is open at midnight; luminous benches provide safe respite. Late-night closings thrive in midweek, especially along the transit corridor. A night market is open around the corner. Posters are up for a midnight concert at the local park, with provisions for audio headsets to coexist with the residential district. This manifesto posits a kind of revolutionary adaptation – a switch up of night for day. Here, we contemplate: Is it possible to transform negative impressions of darkness by designing optimistic spaces after sunset?

Heat-Related Illnesses.

Climate change is anticipated to continue to adversely affect public health, with heat stress the predominant threat. Accordingly, heat-related illness is predicted to increase as extremely hot days become more frequent. Heat stroke, the most serious heat-related illness, is a medical emergency that may be fatal if it is not promptly recognized, addressed with early and rapid cooling, and accompanied by multidisciplinary supportive care as clinically indicated. Heat stroke is a preventable illness that occurs in 2 distinct forms-classic and exertional-that have distinct demographic profiles and clinical courses but similar management paradigms.

Feeling the heat: associations among daily ambient temperatures, extreme heat days and risk mortality in Australian dogs from New South Wales (1997-2017).

Global warming is expected to drive increases in daily temperatures and extreme heatwaves which are in turn expected to lead to increases in heat-related illness (HRI) morbidity and mortality in humans and animals, including dogs. The most severe form of HRI is heat stroke which is potentially fatal in dogs. The temperature range that increases the risk of mortality in dogs, and the impact of heatwaves, is not known. Twenty years of veterinary data from New South Wales (1997-2017) were analysed to explore potential associations between rates of mortality in dogs and both daily ambient maximum temperatures and extreme heat days. Extreme heat days were defined as any day that was over the 95th percentile (32°C) of daily maximum temperature in the study region across the study period. Results show that mortality increased as daily maximum temperature exceeded 25°C. There was a broadly linear increase of 0.6% (95% CI: 0.1% to 1%) in the risk of mortality for each 1°C increase in daily maximum temperature above 25°C. There was a 9.5% increased risk (95% CI: 4.3% to 15%) of mortality on extreme heat days compared with nonextreme heat days. Controlling for the effects of temperature, risk of mortality on public holidays increased 1.5 times (155%, 95% CI: 137% to 173%) compared with nonpublic holidays, and Sundays had nearly double the risk of mortality compared with all other days of the week. New Year's Day had the highest reported rate of mortality, followed by Christmas Day. This information should be used to inform veterinary public health policies in general and to inform key messaging about reducing the risk of death in dogs due to high ambient temperatures.

The health impact of climate change on the women in reproductive age: a study of coastal communities in Satkhira, Bangladesh

BackgroundClimate change and health issues pose a global threat, particularly in developing countries like Bangladesh. Within the socio-economic structure in coastal regions, women played a crucial role in contributing livelihood and living resources, while new climatic ecology creates chaotic relationships between environment and human health. The emerging adverse climatic ecology is directly and indirectly affecting them in the sphere of their both outdoor and indoor activism. This study explores the health impacts of climate change on the women of reproductive age (ages between 14 and 49 from the Bangladeshi perspective) living in coastal communities, i.e., Satkhira, Bangladesh.MethodsTo choose study locations, this study conducted a literature survey to find out the most vulnerable coastal region of Bangladesh. The study has selected the five most vulnerable unions of Shyamnagar upazila in Satkhira district. This study adopted a multi-method approach combining in-depth interviews and KIIs. Based on this methodological guide, this study interviewed 25 women and 5 married men, while their responses have further been supplemented and validated by KIIs with health workers and medical officers.ResultsFindings show that climate change posture to new climatic ecology facilitating adverse situations that lead to the intrusion of saline water within communities, lack of fresh and drinkable water, women exposure to waterborne diseases resulting from both salinity and scarcity of fresh usable water, skin disorders, gynaecological and reproductive illnesses, and vector-borne diseases. Women also bear an encountered burden in their struggle to acquire water and good health, including limited hygiene facilities and maternal care. This dilemma is even worsened during the summer season, which exposes women to heat waves, resulting in physical complications such as anaemia, pregnancy risks, heat stroke, dehydration, hypertension and psychological complications like anxiety, stress and depression.ConclusionBreaches in awareness and prevention practices were outlined from the study, as there is a need to realize integrated solutions to address the environmental and health challenges of the populations. Further, there is an absolute need to continue improving access to safe water, healthcare services, and education as a way to build resilience in affected communities.

Xuebijing Promotes HMGB1-Mediated Autophagy to Alleviate Oxidative Stress and Inflammation in Heat Stroke-Induced Brain Damage.

Heat stroke (HS) is a life-threatening condition with complex underlying mechanisms, posing challenges for pharmacological treatment. Xuebijing (XBJ) can effectively relieve HS-induced brain injury, but its molecular mechanism is not well-established. This study was conducted to investigate the mechanisms underlying the protective role of XBJ in HS-induced brain injury. HS-induced mice and cell models were established to elucidate the protective effects and underlying mechanisms of XBJ on HS-induced brain injury in vivo and in vitro. HMGB1 knockout (HMGB1-/-) mice and HMGB1 silencing in primary neuronal cells were used to study the effects of XBJ on HMGB1 in HS. Assessments included survival rate, neuronal damage score, and pathological changes. Various techniques such as Western blot, Transmission Electron Microscope (TEM), immunofluorescence staining, RT-qPCR, commercial kits, TUNEL assay, CCK-8, EdU, flow cytometry, and Co-IP assay were employed to assess autophagy, reactive oxygen species (ROS) levels, oxidative stress, inflammation, neuronal apoptosis, and protein complexes. Data revealed that XBJ ameliorated brain damage and neuron apoptosis in HS-exposed mice and promoted autophagy while inhibiting oxidative stress and inflammatory responses, both in vivo and in vitro. Additionally, XBJ alleviated neuronal brain damage, neuron apoptosis, oxidative stress, and inflammatory responses in HS via inducing autophagy. Furthermore, XBJ promoted the cytoplasmic translocation of HMGB1 from the nucleus and competed with Bcl-2 for binding to Beclin1. Moreover, HMGB1-/- mice and HMGB1 silencing in primary neuronal cells displayed reduced autophagy and enhanced inflammatory responses, both in vivo and in vitro. XBJ protects against HS-induced brain injury via a mechanism involving the autophagy-inflammation pathway mediated by HMGB1.

Faecal microbiome, gastrointestinal integrity, inflammation and thermoregulation in recent exertional heat illness patients and matched controls.

The gastrointestinal (GI) microbiota and GI barrier integrity are hypothesised to contribute to exertional heat illness (EHI) aetiology. We compared the faecal microbiome, GI barrier integrity, inflammation and thermoregulation of 29 recent (∼4 months) EHI patients (a group with elevated EHI risk) and 29 control individuals without prior EHI history, matched for variables influencing thermoregulation and GI microbiota. Participants completed an exercise heat tolerance assessment (HTA), with faecal microbiome assessed by 16S rRNA gene amplicon sequencing of stool samples and blood biomarkers of GI barrier integrity and inflammation measured pre- and post-HTA. With the exception of the Simpson index (patient=0.97±0.01vs. control=0.98±0.00, P=0.030), there were no between-groups differences in faecal microbiome composition (α-diversity, β-diversity, relative abundance, differential abundance), GI barrier integrity, inflammation or terminal thermoregulatory indices. Individuals were subsequently classified as heat tolerant (n=46) or intolerant (n=12) on the basis of the HTA. Heat intolerant individuals demonstrated lower sudomotor response (intolerant=0.53 (0.17) vs. tolerant=0.62 (0.20) Lm-2h-1, P=0.011) despite greater thermoregulatory strain (e.g., terminal Trec: intolerant=39.20±0.31vs. tolerant=38.80±0.31°C, P<0.001), lower Firmicutes:Bacteroidota ratio (intolerant=3.7 (0.6) vs. tolerant=4.5 (2.0), P=0.019) and higher plasma [sCD14] (P=0.014), but other aspects of faecal microbiome, GI integrity or inflammation did not differ from heat tolerant individuals. In conclusion, the faecal microbiome composition and the GI barrier integrity and inflammatory responses to exercise heat-stress showed limited differences between recent EHI patients and matched controls, or between individuals classified as heat intolerant or heat tolerant and are unlikely to explain elevated EHI risk in recent EHI patients, or heat intolerance.

Heat exhaustion and heat stroke among active component members of the U.S. Armed Forces, 2020-2024.

In 2024, the crude incidence rates of heat stroke and heat exhaustion were 36.4 and 183.9 cases per 100,000 person-years, respectively. After a period of decline in rates of incident heat stroke from 2020 through 2023, during the 2024 surveillance period an increase was observed. When considering only heat exhaustion, incident rates increased each year during the 5-year surveillance period, from 2020 through 2024. In 2024, higher rates of heat stroke were observed among male service members, when compared to their female counterparts, as well as among non-Hispanic White service members compared to service members of other races and ethnicities. Female service members and non-Hispanic Black service members experienced higher rates of heat exhaustion than their male counterparts and service members of other races and ethnicities, respectively. Heat illness rates were also higher among those younger than age 20 years, Marine Corps and Army service members, and recruit trainees. To mitigate the personal and organizational impacts of heat illness, leaders, training cadres, and supporting medical and safety personnel must inform both their subordinate and supported service members of heat illness risks, preventive measures, early signs and symptoms of illness, and appropriate interventions. In 2024, the crude annual incidence rate of heat stroke increased 16.5%, following a 4-year decrease of 10.8% from 2020 to 2023. All services, apart from the Space Force and Coast Guard, had a higher rate of heat stroke in 2024 than in 2023. The crude annual incidence rate of heat exhaustion increased 52.3% from 2020 to 2024, with incremental increases annually. Increased rates of heat exhaustion in 2024 from 2023 were observed in the Army, Marine Corps, and Coast Guard.

Comparison of Rectal and Gastrointestinal Core Temperatures During Heat Tolerance Testing

Background and Objectives: Military capability may be reduced in hot environments with individuals at risk of exertional heat stroke (EHS). Heat tolerance testing (HTT) can be used to indicate readiness to return to duty following EHS. HTT traditionally relies on rectal core temperature (Tre) assessment via a rectal probe. This study investigated the use of gastrointestinal core temperature (Tgi) as an alternative to Tre during HTT. A secondary aim was to compare physiological factors between heat-tolerant and heat-intolerant trials. Materials and Methods: Australian Defence Force personnel undergoing HTT following known or suspected heat stroke volunteered (n = 23 cases participating in 26 trials) along with 14 controls with no known heat illness history. Confusion matrices enabled comparison of HTT outcome based on Tgi and Tre. The validity of Tgi compared to Tre during HTT was assessed using correlation and bias. Comparisons between heat-tolerant and intolerant trials were performed using non-parametric tests. Results: Although Tgi correlated closely with Tre (Spearman’s rank correlation = 0.893; median bias 0.2 °C) there was no consistent pattern in the differences between measures. Importantly, the two measures only agreed on heat tolerance outcome in 80% of trials with Tgi failing to detect heat intolerance identified by Tre in 6 of 8 trials. If Tgi was relied upon for diagnostic outcome, return to duty may occur before full recovery. None of the assessed covariates were related to the difference between Tre and Tgi. In addition, resting heart rate and systolic blood pressure were significantly lower and body surface area to mass ratio significantly higher in heat-tolerant compared to intolerant trials. Conclusions: It is not recommended to rely on Tgi instead of Tre during HTT. Resting heart rate and systolic blood pressure findings point to the importance of aerobic exercise in conveying heat tolerance along with body composition.

Clinical Profile and Outcomes of Patients with Heat Stroke: An Observational Study from a Tertiary Care Center in Eastern India

Abstract Background: Heat stroke is a growing public health concern exacerbated by rising temperatures and prolonged heat waves. This study examines the clinical profile, prognostic markers, and outcomes of heat stroke patients presenting to a tertiary care center in India and compares findings with previous global studies. Objective: The objective of this study was to analyze the clinical profile, prognostic markers, and outcomes of heat stroke patients presenting to a tertiary care center in India and to compare findings with previous global studies. Materials and Methods: A retrospective study was conducted between March and July 2024 at a tertiary care center in Eastern India. Data on demographics, clinical parameters, laboratory values, and outcomes were collected and analyzed using appropriate statistical methods. Results: During the study period, 43 patients were admitted with heat stroke, the mean age (in years) was 57, and 67% were male. The overall mortality rate was 21%. Significant predictors of mortality included hypotension (systolic blood pressure &lt;100 mmHg, P = 0.040), tachypnea (respiratory rate &gt;20/min, P = 0.001), Glasgow Coma Scale score &lt;9 (P &lt; 0.001), elevated creatinine, and multi-organ dysfunction syndrome involving the renal system and central nervous system (P &lt; 0.01). Younger, active individuals were disproportionately affected due to occupational exposure to high ambient temperatures. Conclusion: Our findings highlight key clinical and biochemical predictors of poor outcomes in heat stroke. Indian patients, being younger and functionally active, may face increased exposure to high ambient temperatures.

Pre-hospital cooling in community-acquired heat stroke (CAHS): evidence, challenges, and strategies

BackgroundHeat stroke (HS) is a critical medical emergency characterized by severe hyperthermia and central nervous system dysfunction, occurring predominantly in conditions of high ambient temperatures or through physical exertion. With rising global temperatures, the incidence and severity of HS are expected to increase, presenting substantial public health challenges.ObjectivesThis review synthesizes current evidence on cooling methods for HS, addresses challenges in managing community-acquired heat stroke (CAHS), and proposes strategies to enhance pre-hospital and emergency department (ED) care.MethodsWe evaluated existing literature on cooling strategies, focusing on different subtypes of HS (classic and exertional) and the efficacy of rapid cooling techniques. In addition, we reviewed epidemiological data and proposed a subclassification of HS into supervised and community-acquired heat stroke to better understand healthcare accessibility impacts.ResultsWater, particularly cold water immersion, is recognized as the most effective medium for cooling HS due to its superior thermal properties. Rapid cooling (> 0.15 °C/min) is crucial for survival, significantly reducing case fatality rates and medical complications. Supervised HS, often managed promptly at athletic or military events, shows near-zero fatality rates with immediate cooling. In contrast, CAHS presents unique challenges due to delayed medical intervention and lack of immediate cooling resources. Current strategies to improve CAHS management include public education, dispatcher-guided first aid, and pre-hospital cooling techniques such as internal cooling with cold saline and gastric lavage.ConclusionsEffective HS management hinges on rapid cooling, with water immersion being the gold standard. To mitigate the rising burden of HS, particularly in community settings, there is a need for enhanced public awareness, training for emergency responders, and improved pre-hospital equipment. Future strategies should focus on integrating cooling interventions into emergency response protocols and ensuring timely access to cooling resources in both pre-hospital and ED settings.

Study of the Present and Future Scenario Heatwaves and Heat Stress for the Few Important States of India

India is highly vulnerable to climate change and is going to increase its average annual temperature over the next few decades. The impact of heatwaves and related mortality is a concern for the country. In this paper, we aim to study the heatwaves and heat stress-related Heat Index vulnerability using heat index temperature. In this analysis, a heat index temperature is calculated based on temperature and relative humidity for six different states (Delhi, West Bengal, Punjab, Uttar Pradesh, Andhra Pradesh, and Madhya Pradesh) of India to determine the heat stress vulnerability for which heat cramps and heat strokes are possible. Our analysis shows that most of the heatwaves and severe heatwaves occurred during 2010 for all the states. The heatwaves are observed only in the summer months. All the states of our study reached the Extreme Caution category of the Heat Index showing the Danger to Extreme Danger category during April to June. Future projection scenarios show an increase in heat stress-related vulnerability. SSP2-4.5 scenario showed that Delhi, Punjab, and West Bengal reached an Extreme Danger state during June for which death due to heat strokes is possible under continued exposure to heatwaves. The HI related vulnerability of SSP5-8.5 is like SSP2-4.5 except for Andhra Pradesh which shows an Extreme Danger state in May and June during which heat strokes are possible under continued exposure to heatwaves. This study provides spatial variability of heat stress and Heat Index vulnerability which may help adopt future strategies for heat-related policy implication.

Heat-Related Illness Among US Patients Experiencing Homelessness

This cross-sectional study compares heat-related emergency department visits and hospitalizations among persons experiencing homelessness and nonhomeless populations.

Influence of the South Asian High and Western Pacific Subtropical High Pressure Systems on the Risk of Heat Stroke in Japan

Weather patterns substantially influence extreme weathers in Japan. Extreme high temperature events can cause serious health problems, including heat stroke. Therefore, understanding weather patterns, along with their impacts on human health, is critically important for developing effective public health measures. This study examines the impact of weather patterns on heat stroke risk, focusing on a two-tiered high-pressure system (DH: double high) consisting of a lower tropospheric western Pacific subtropical high (WPSH) and an overlapping upper tropospheric South Asian high (SAH), which is thought to cause high-temperature events in Japan. In this study, the self-organizing map technique was utilized to investigate the relationship between pressure patterns and the number of heat stroke patients in four populous cities. The study period covers July and August from 2008 to 2021. The results show that the average number of heat stroke patients in these cities is higher on DH days than on WPSH days in which SAH is absent. The probability of an extremely high daily number of heat stroke patients is more than twice as high on DH days compared to WPSH days. Notably, this result remains true even when WPSH and DH days are compared within the same air temperature range. This is attributable to the higher humidity and stronger solar radiation under DH conditions, which enhances the risk of heat stroke. Large-scale circulation anomalies similar to the Pacific–Japan teleconnection are found on DH days, suggesting that both high humidity and cloudless conditions are among the large-scale features controlled by this teleconnection. Early countermeasures to mitigate heat stroke risk, including advisories for outdoor activities, should be taken when DH-like weather patterns are predicted.