Is Physiological Equivalent Temperature (PET) a superior screening tool for heat stress risk than Wet-Bulb Globe Temperature (WBGT) index? Eight years of data from the Gothenburg half marathon.

BACKGROUND: The Wet-Bulb Globe Temperature (WBGT) index is a common tool to screen for heat stress for sporting events. However, the index has a number of limitations. Rational indices, such as the physiological equivalent temperature (PET) and Universal Thermal Climate Index (UTCI), are potential alternatives. AIM: To identify the thermal index that best predicts ambulance-required assistances and collapses during a city half marathon. METHODS: Eight years (2010-2017) of meteorological and ambulance transport data, including medical records, from Gothenburg's half-marathon were used to analyse associations between WBGT, PET and UTCI and the rates of ambulance-required assistances and collapses. All associations were evaluated by Monte-Carlo simulations and leave-one-out-cross-validation. RESULTS: The PET index showed the strongest correlation with both the rate of ambulance-required assistances (R2=0.72, p=0.008) and collapses (R2=0.71, p=0.008), followed by the UTCI (R2=0.64, p=0.017; R2=0.64, p=0.017) whereas the WBGT index showed substantially poorer correlations (R2=0.56, p=0.031; R2=0.56, p=0.033). PET stages of stress, match the rates of collapses better that the WBGT flag colour warning. Compared with the PET, the WBGT underestimates heat stress, especially at high radiant heat load. The rate of collapses increases with increasing heat stress; large increase from the day before the race seems to have an impact of the rate of collapses. CONCLUSION: We contend that the PET is a better predictor of collapses during a half marathon than the WBGT. We call for further investigation of PET as a screening tool alongside WBGT.

Health status, heat preparation strategies and medical events among elite cyclists who competed in the heat at the 2016 UCI Road World Cycling Championships in Qatar.

PURPOSE: Assess the health status and heat preparation strategies of athletes competing in a World Cycling Championships held in hot ambient conditions (37°C, 25% relative humidity, wet-bulb-globe-temperature 27°C) and monitor the medical events arising during competition. METHODS: 69 cyclists (~9% of the world championships participants) completed a pre-competition questionnaire. Illnesses and injuries encountered by the Athlete Medical Centre (AMC) were extracted from the race reports. RESULTS: 22% of respondents reported illness symptoms in the 10 days preceding the Championships. 57% of respondents had previously experienced heat-related symptoms (cramping most commonly) while 17% had previously been diagnosed with exertional heat illness. 61% of the respondents had undergone some form of heat exposure prior to the Championships, with 38% acclimating for 5 to 30 days. In addition, several respondents declared to live in warm countries and all arrived in Qatar ~5 days prior to their event. 96% of the respondents used a pre-cooling strategy for the time trials and 74% did so before the road race (p<0.001), with ice vests being the most common. The AMC assessed 46 injuries and 26 illnesses in total, with three cyclists diagnosed with heat exhaustion. CONCLUSIONS: The prevalence of previous heat illness in elite cyclists calls for team and event organisation doctors to be trained on heat illness management, including early diagnosis and rapid on-site cooling. Some cyclists had been exposed to the heat prior to the Championships, but few had a dedicated plan, calling for additional education on the importance of heat acclimation. Pre-cooling was widely adopted.

The impact of heatwaves on emergency department visits in Brisbane, Australia: a time series study.

INTRODUCTION: The acute health effects of heatwaves in a subtropical climate and their impact on emergency departments (ED) are not well known. The purpose of this study is to examine overt heat-related presentations to EDs associated with heatwaves in Brisbane. METHODS: Data were obtained for the summer seasons (December to February) from 2000-2012. Heatwave events were defined as two or more successive days with daily maximum temperature ≥34°C (HWD1) or ≥37°C (HWD2). Poisson generalised additive model was used to assess the effect of heatwaves on heat-related visits (International Classification of Diseases (ICD) 10 codes T67 and X30; ICD 9 codes 992 and E900.0). RESULTS: Overall, 628 cases presented for heat-related illnesses. The presentations significantly increased on heatwave days based on HWD1 (relative risk (RR) = 4.9, 95% confidence interval (CI): 3.8, 6.3) and HWD2 (RR = 18.5, 95% CI: 12.0, 28.4). The RRs in different age groups ranged between 3-9.2 (HWD1) and 7.5-37.5 (HWD2). High acuity visits significantly increased based on HWD1 (RR = 4.7, 95% CI: 2.3, 9.6) and HWD2 (RR = 81.7, 95% CI: 21.5, 310.0). Average length of stay in ED significantly increased by >1 hour (HWD1) and >2 hours (HWD2). CONCLUSIONS: Heatwaves significantly increase ED visits and workload even in a subtropical climate. The degree of impact is directly related to the extent of temperature increases and varies by socio-demographic characteristics of the patients. Heatwave action plans should be tailored according to the population needs and level of vulnerability. EDs should have plans to increase their surge capacity during heatwaves.

Heat exhaustion and heat stroke among active component members of the U.S. Armed Forces, 2019-2023.

The most serious types of heat illnesses, heat exhaustion and heat stroke, are occupational hazards associated with many of the military's training and operational environments. These illnesses can typically be prevented by appropriate situational awareness, risk management strategies, along with effective countermeasures. In 2023, the crude incidence of heat stroke and heat exhaustion were 31.7 and 172.7 cases per 100,000 person-years, respectively. The rates of incident heat stroke declined during the 2019 to 2023 surveillance period, but rates of incident heat exhaustion increased over the same period. In 2023, higher rates of heat stroke were observed among male service members compared to their female counterparts, and female service members experienced higher rates of heat exhaustion compared to male personnel. Heat illness rates were also higher among those younger than age 20, Marine Corps and Army service members, non-Hispanic Black service members, and recruits. Leaders, training cadres, and supporting medical and safety personnel must inform their subordinate and supported service members of heat illness risks, preventive measures, early signs and symptoms of illness, and appropriate interventions.

Heat Exhaustion and Heat Stroke Among Active Component Members of the U.S. Armed Forces, 2018-2022.

The most serious types of heat illness, heat exhaustion and heat stroke, are occupational hazards of the military's training and operational environments. These conditions can be mitigated with appropriate situational aware-ness and effective countermeasures. In 2022, the crude incidence rates of heat stroke and heat exhaustion among active component service members were 32.1 and 147.7 per 100,000 person-years, respectively. The rates of incident heat stroke and heat exhaustion generally declined during the 2018 to 2022 surveillance period. In 2022, those at highest risk were men, those younger than age 20, Marine Corps and Army members, recruit trainees, and those in combat-specific occupations. Leaders, training cadres, and supporting medical personnel must inform their supervised and supported service members of heat illness risks, preventive measures, early signs and symptoms, and first-responder actions.

Heat- and cold-induced injuries in athletes: evaluation and management.

Both extreme heat and cold can be challenging for athletes during training and competition. One role of the team physician is to educate coaches and athletes on the risks of exposure to these conditions and how to best prevent and manage their adverse effects. Heat illness varies in degree from mild to severe, with the most severe forms being potentially fatal. Cold exposure can result in systemic effects and peripheral injury to the extremities.

Exertional heat illness at Fort Benning, GA: Unique insights from the Army Heat Center.

The Army Heat Center at Fort Benning, GA was established to identify and disseminate best practices for the prevention, field care, evacuation, hospital care, and return to duty of exertional heat casualties. During the 2017-2021 surveillance period, there were 1,911 heat casualties treated at Ft. Benning's Martin Army Community Hospital. Most patients were junior enlisted and officer personnel who were engaged in initial entry training. Heat exhaustion, heat injury, heat stroke, and hyponatremia accounted for 52.6%, 18.4%, 18.2%, and 2.0% of total heat illnesses, respectively. The annual proportion of heat casualties that were due to heat exhaustion rose steadily during the surveillance period, reaching 77.7% in 2021, while the incidence of heat injury and heat stroke did not increase during this period. Data are presented on the occurrence of clusters of heat illness, the association of cases of heat stroke with arduous physical activities, and the seasonal variation in incidence of heat illnesses. It is important that unit leaders and trainers understand the risk factors for heat illness among those being trained and that early first aid measures be employed in the field (especially rapid cooling).

Heat-related illnesses during the 2003 heat wave in an emergency service.

INTRODUCTION: This study describes patients admitted to an urban emergency service in France during the 2003 heat wave. Patients with heat-related illnesses were studied and comparison was made between those who died and survivors. METHODS: A retrospective study of about 760 records concerning 726 patients aged over 65 years admitted during August 2003 to a French emergency department. RESULTS: After review of the medical records, 42 patients had heat-related illnesses. Heat-related illnesses were not diagnosed by the treating physician in any of the patients. The patients were more likely to live in institutional care and used more psychotropic medications. Hyperthermia and acute cognitive impairment were the main reasons for admission to the emergency department. The patients had a higher heart rate and body temperature and more dyspnoea and central nervous system dysfunction than those without heat-related illnesses. Twelve patients (28.6%) with heat-related illnesses died in the emergency unit or after admission to hospital. Temperature, heart rate and plasma creatinine levels were higher in those who died than in survivors with heat-related illnesses. CONCLUSION: Heat-related illnesses are a group of underestimated and underdiagnosed conditions with high morbidity and mortality rates.

[Community-based prevention of climate-associated health risks]. / Prävention klimabedingter Gesundheitsrisiken in der Kommune.

BACKGROUND: Climate changes and their impact on public health services are presenting officials with new challenges. The Klimzug Nordhessen project provides a framework for the development of suitable adaptation strategies to deal with climate changes. PROJECT: The demographic and climatic circumstances in the region in and surrounding Kassel require a focus on the prevention of heat-caused morbidity and mortality among adults 75 or more years old. The Klimzug Nordhessen project assesses the feasibility of heat monitoring for city and county regions and collects data about the temperature-related comfort of older people. The main focus of the project is the development of prevention strategies for older people who live at home in climatic and demographic high-risk regions. CONCLUSIONS: In the face of inadequate data, the current cooperation between science and practice seems to be an appropriate base for the development of verifiable empirical methods and instruments as well as evidence-based prevention strategies at the communal level.

Update: Heat illness, active component, U.S. Armed Forces, 2018.

In 2018, there were 578 incident diagnoses of heat stroke and 2,214 incident diagnoses of heat exhaustion among active component service members. The overall crude incidence rates of heat stroke and heat exhaustion diagnoses were 0.45 cases and 1.71 cases per 1,000 person-years, respectively. In 2018, subgroup-specific rates of incident heat stroke diagnoses were highest among males and service members less than 20 years old, Asian/Pacific Islanders, Marine Corps and Army members, recruit trainees, and those in combatspecific occupations. Subgroup-specific incidence rates of heat exhaustion diagnoses in 2018 were notably higher among service members less than 20 years old, Asian/Pacific Islanders, Army and Marine Corps members, recruit trainees, and service members in combat-specific occupations. During 2014- 2018, a total of 325 heat illnesses were documented among service members in Iraq and Afghanistan; 8.6% (n=28) were diagnosed as heat stroke. Commanders, small unit leaders, training cadre, and supporting medical personnel must ensure that the military members whom they supervise and support are informed about the risks, preventive countermeasures, early signs and symptoms, and first-responder actions related to heat illnesses.

A real-time heat strain risk classifier using heart rate and skin temperature.

Heat injury is a real concern to workers engaged in physically demanding tasks in high heat strain environments. Several real-time physiological monitoring systems exist that can provide indices of heat strain, e.g. physiological strain index (PSI), and provide alerts to medical personnel. However, these systems depend on core temperature measurement using expensive, ingestible thermometer pills. Seeking a better solution, we suggest the use of a model which can identify the probability that individuals are 'at risk' from heat injury using non-invasive measures. The intent is for the system to identify individuals who need monitoring more closely or who should apply heat strain mitigation strategies. We generated a model that can identify 'at risk' (PSI 7.5) workers from measures of heart rate and chest skin temperature. The model was built using data from six previously published exercise studies in which some subjects wore chemical protective equipment. The model has an overall classification error rate of 10% with one false negative error (2.7%), and outperforms an earlier model and a least squares regression model with classification errors of 21% and 14%, respectively. Additionally, the model allows the classification criteria to be adjusted based on the task and acceptable level of risk. We conclude that the model could be a valuable part of a multi-faceted heat strain management system.

[The importance of atmospheric heat waves for health service in already altered people]. / Klimatische Hitzewellen und deren Konsequenzen für die gesundheitliche Betreuung vorgeschädigter Personen.

The paper deals with the problems of heat exhaustion and heat stroke related to exercise or elevation of environmental temperature. After recommending a classification of heat disorders, the different clinical symptoms are presented. Old people and people with preexisting diseases are particularly affected and in danger. Therapeutic measures have to consider different mechanisms of an alteration of liquid and salt balance.

Pattern and determinants of hospitalization during heat waves: an ecologic study.

BACKGROUND: Numerous studies have investigated mortality during a heatwave, while few have quantified heat associated morbidity. Our aim was to investigate the relationship between hospital admissions and intensity, duration and timing of heatwave across the summer months. METHODS: The study area (Veneto Region, Italy) holds 4577408 inhabitants (on January 1st, 2003), and is subdivided in seven provinces with 60 hospitals and about 20000 beds for acute care. Five consecutive heatwaves (three or more consecutive days with Humidex above 40 degrees C) occurred during summer 2002 and 2003 in the region. From the regional computerized archive of hospital discharge records, we extracted the daily count of hospital admissions for people aged >or=75, from June 1 through August 31 in 2002 and 2003. Among people aged over 74 years, daily hospital admissions for disorders of fluid and electrolyte balance, acute renal failure, and heat stroke (grouped in a single nosologic entity, heat diseases, HD), respiratory diseases (RD), circulatory diseases (CD), and a reference category chosen a priori (fractures of the femur, FF) were independently analyzed by Generalized Estimating Equations. RESULTS: Heatwave duration, not intensity, increased the risk of hospital admissions for HD and RD by, respectively, 16% (p < .0001) and 5% (p < .0001) with each additional day of heatwave duration. At least four consecutive hot humid days were required to observe a major increase in hospital admissions, the excesses being more than twofold for HD (p < .0001) and about 50% for RD (p < .0001). Hospital admissions for HD peaked equally at the first heatwave (early June) and last heatwave (August) in 2004 as did RD. No correlation was found for FF or CD admissions. CONCLUSION: The first four days of an heatwave had only minor effects, thus supporting heat health systems where alerts are based on duration of hot humid days. Although the finding is based on a single late summer heatwave, adaptations to extreme temperature in late summer seem to be unlikely.

International Classification of Disease Coding of Exertional Heat Illness in U.S. Army Soldiers.

INTRODUCTION: The severity of exertional heat illnesses (EHI) ranges from relatively minor heat exhaustion to potentially life-threatening heat stroke. Epidemiological surveillance of the types of and trends in EHI incidence depends on application of the appropriate International Classification of Disease, 9th Revision (ICD-9) diagnostic code. However, data examining whether the appropriate EHI ICD-9 code is selected are lacking. The purpose of this study was to determine whether the appropriate ICD-9 code is selected in a cohort of EHI casualties. MATERIALS AND METHODS: Chart reviews of 290 EHI casualties that occurred in U.S. Army soldiers from 2009 to 2012 were conducted. The ICD-9 diagnostic code was extracted, as were the initial and peak values for aspartate transaminase, alanine transaminase, creatine kinase, and creatinine. Diagnostic criteria for heat injury and heat stroke include evidence of organ and/or tissue damage; 2 out of 3 of the following must have been met to be considered heat injury (ICD-9 code 992.8) or heat stroke (ICD-9 code 992.0): aspartate transaminase/ alanine transaminase fold increase >3, creatine kinase fold increase >5, and/or creatinine ≥1.5mg/dL. Contingency tables were constructed from which sensitivity, specificity, and positive and negative predictive value were calculated. RESULTS: The 290 cases in this cohort represent ∼29% of all EHI at Fort Benning and ∼6% of all EHI Army-wide during the study period. There were 80 cases that met the laboratory diagnostic criteria for heat injury/stroke, however of those, 28 cases were diagnosed as an EHI other than heat injury/stroke (sensitivity = 0.65). 210 cases did not meet the laboratory diagnostic criteria, but 66 of those were incorrectly diagnosed as heat injury or heat stroke (specificity = 0.69). Positive and negative predictive values were 0.44 and 0.84, respectively. In total, the incorrect ICD-9 code was applied to 94 of 290 total cases. CONCLUSIONS: Our data suggest that caution is warranted when examining epidemiological surveillance data on EHI severity, as there was disagreement between the laboratory data and the selected ICD-9 code in ∼1/3 of all cases in this cohort. Of note is the lack of an ICD-9 or -10 code for heat injury; we recommend coding for heat exhaustion as the primary diagnosis and additional codes to capture the accompanying muscle, tissue, and/or organ damage.

Frequency of Extreme Heat Event as a Surrogate Exposure Metric for Examining the Human Health Effects of Climate Change.

Epidemiological investigation of the impact of climate change on human health, particularly chronic diseases, is hindered by the lack of exposure metrics that can be used as a marker of climate change that are compatible with health data. Here, we present a surrogate exposure metric created using a 30-year baseline (1960-1989) that allows users to quantify long-term changes in exposure to frequency of extreme heat events with near unabridged spatial coverage in a scale that is compatible with national/state health outcome data. We evaluate the exposure metric by decade, seasonality, area of the country, and its ability to capture long-term changes in weather (climate), including natural climate modes. Our findings show that this generic exposure metric is potentially useful to monitor trends in the frequency of extreme heat events across varying regions because it captures long-term changes; is sensitive to the natural climate modes (ENSO events); responds well to spatial variability, and; is amenable to spatial/temporal aggregation, making it useful for epidemiological studies.

Responding to heatwave intensity: Excess Heat Factor is a superior predictor of health service utilisation and a trigger for heatwave plans.

OBJECTIVE: To determine which measures of heatwave have the greatest predictive power for increases in health service utilisation in Perth, Western Australia. METHODS: Three heatwave formulas were compared, using Poisson or zero-inflated Poisson regression, against the number of presentations to emergency departments from all causes, and the number of inpatient admissions from heat-related causes. The period from July 2006 to June 2013 was included. A series of standardised thresholds were calculated to allow comparison between formulas, in the absence of a gold standard definition of heatwaves. RESULTS: Of the three heatwave formulas, Excess Heat Factor (EHF) produced the most clear dose-response relationship with Emergency Department presentations. The EHF generally predicted periods that resulted in a similar or higher rate of health service utilisation, as compared to the two other formulas, for the thresholds examined. CONCLUSIONS: The EHF formula, which considers a period of acclimatisation as well as the maximum and minimum temperature, best predicted periods of greatest health service demand. The strength of the dose-response relationship reinforces the validity of the measure as a predictor of hazardous heatwave intensity. IMPLICATIONS: The findings suggest that the EHF formula is well suited for use as a means of activating heatwave plans and identifies the required level of response to extreme heatwave events as well as moderate heatwave events that produce excess health service demand.

A Spatial Framework to Map Heat Health Risks at Multiple Scales.

In the last few decades extreme heat events have led to substantial excess mortality, most dramatically in Central Europe in 2003, in Russia in 2010, and even in typically cool locations such as Vancouver, Canada, in 2009. Heat-related morbidity and mortality is expected to increase over the coming centuries as the result of climate-driven global increases in the severity and frequency of extreme heat events. Spatial information on heat exposure and population vulnerability may be combined to map the areas of highest risk and focus mitigation efforts there. However, a mismatch in spatial resolution between heat exposure and vulnerability data can cause spatial scale issues such as the Modifiable Areal Unit Problem (MAUP). We used a raster-based model to integrate heat exposure and vulnerability data in a multi-criteria decision analysis, and compared it to the traditional vector-based model. We then used the Getis-Ord G(i) index to generate spatially smoothed heat risk hotspot maps from fine to coarse spatial scales. The raster-based model allowed production of maps at spatial resolution, more description of local-scale heat risk variability, and identification of heat-risk areas not identified with the vector-based approach. Spatial smoothing with the Getis-Ord G(i) index produced heat risk hotspots from local to regional spatial scale. The approach is a framework for reducing spatial scale issues in future heat risk mapping, and for identifying heat risk hotspots at spatial scales ranging from the block-level to the municipality level.

Epidemic classical heat stroke: clinical characteristics and course of 28 patients.

Patients with classical heat stroke are different in many ways from those with exertional injury; contrasts included difference in demographic factors, prior general health, in-hospital complications and laboratory abnormalities (lactate, liver enzymes, pH, electrolytes). Severe hyperkalemia, acute renal failure, rhabdomyolysis and disseminated intravascular coagulation often dominate the course of patients with exertional heat stroke but are uncommon in those with classical heat stroke (Table 4). While lactic acidosis is the rule in exertional injury, it is somewhat unusual in patients with classical heat stroke and when above 3 mmoles/L predicts a poor outcome or death. In spite of the advanced age and multiple medical problems of the patients with classical heat stroke, careful attention to early and aggressive cooling and scrutiny for potential complications can result in salvage of most patients.

Elevated pyrogenic cytokines in heatstroke.

STUDY OBJECTIVES: Heatstroke, characterized by hyperthermia and neurologic abnormalities, can cause shock, adult respiratory distress syndrome, and multiorgan failure culminating in death. The mediation of metabolic changes and tissue damage is not fully understood. Recent evidence suggests the involvement of endotoxin, tumor necrosis factor alpha (TNF-alpha), and interleukin 1 alpha (IL-1 alpha) and we hypothesized that other pyrogenic cytokines may be implicated. DESIGN: Prospective analysis. SETTING: Heatstroke Center in Makkah (Mecca), Saudi Arabia. MEASUREMENTS AND RESULTS: We measured plasma IL-1 beta, IL-6, and interferon gamma (INF-gamma) concentrations by enzyme-linked immunosorbent assay in 28 heatstroke patients at the time of hospital admission (precooling) and after complete cooling (postcooling), and in 10 normal control subjects. We measured C-reactive protein (CRP) as a marker of acute phase response and calculated severity of illness using the simplified acute physiology score. Twenty-five male and 3 female subjects had mean (+/- SEM) rectal temperature of 41.2 +/- 0.2 degrees C. IL-6, IL-1 beta, and INF-gamma concentrations were elevated in 100 percent, 39 percent, and 50 percent of patients to (mean +/- SEM) 220 +/- 44 pg/ml, 42 +/- 14 pg/ml, and 1,180 +/- 879 pg/ml, respectively (normal control values: < 3.5 pg/ml, < 4.5 pg/ml, < 20 pg/ml). The CRP value was elevated in 72 percent of patients to 152 +/- 40 mg/L (control value: 0 to 17 mg/L). The IL-6 concentrations correlated with severity of illness (r = 0.516, p = 0.03); two patients with the highest concentrations died. There was no significant correlation between circulating levels of IL-6, IL-1 beta, INF-gamma, and temperature, or between IL-6, IL-1 beta, and CRP. Postcooling, IL-6, and IL-1 beta were still above normal control values; INF-gamma could be detected in one patient only. CONCLUSION: Our findings of elevated circulating IL-6, IL-1 beta, and INF-gamma in the presence of acute phase response, and correlation with severity of illness, suggest that these cytokines have a role in the pathogenesis of heatstroke, which could lead to new therapeutic strategies.