Do heat events pose a greater health risk for individuals with type 2 diabetes?

Interaction between Extreme Temperature Events and Fine Particulate Matter on Cardiometabolic Multimorbidity: Evidence from Four National Cohort Studies

Accumulating evidence linked extreme temperature events (ETEs) and fine particulate matter (PM2.5) to cardiometabolic multimorbidity (CMM); however, it remained unknown if and how ETEs and PM2.5 interact to trigger CMM occurrence. Merging four Chinese national cohorts with 64,140 free-CMM adults, we provided strong evidence among ETEs, PM2.5 exposure, and CMM occurrence. Performing Cox hazards regression models along with additive interaction analyses, we found that the hazards ratio (HRs) of CMM occurrence associated with heatwave and cold spell were 1.006-1.019 and 1.063-1.091, respectively. Each 10 μg/m3 increment of PM2.5 concentration was associated with 17.9% (95% confidence interval: 13.9-22.0%) increased risk of CMM. Similar adverse effects were also found among PM2.5 constituents of nitrate, organic matter, sulfate, ammonium, and black carbon. We observed a synergetic interaction of heatwave and PM2.5 pollution on CMM occurrence with relative excess risk due to the interaction of 0.999 (0.663-1.334). Our study provides novel evidence that both ETEs and PM2.5 exposure were positively associated with CMM occurrence, and the heatwave interacts synergistically with PM2.5 to trigger CMM.

Indoor overheating: A review of vulnerabilities, causes, and strategies to prevent adverse human health outcomes during extreme heat events

The likelihood of exposure to overheated indoor environments is increasing as climate change is exacerbating the frequency and severity of hot weather and extreme heat events (EHE). Consequently, vulnerable populations will face serious health risks from indoor overheating. While the relationship between EHE and human health has been assessed in relation to outdoor temperature, indoor temperature patterns can vary markedly from those measured outside. This is because the built environment and building characteristics can act as an important modifier of indoor temperatures. In this narrative review, we examine the physiological and behavioral determinants that influence a person's susceptibility to indoor overheating. Further, we explore how the built environment, neighborhood-level factors, and building characteristics can impact exposure to excess heat and we overview how strategies to mitigate building overheating can help reduce heat-related mortality in heat-vulnerable occupants. Finally, we discuss the effectiveness of commonly recommended personal cooling strategies that aim to mitigate dangerous increases in physiological strain during exposure to high indoor temperatures during hot weather or an EHE. As global temperatures continue to rise, the need for a research agenda specifically directed at reducing the likelihood and impact of indoor overheating on human health is paramount. This includes conducting EHE simulation studies to support the development of consensus-based heat mitigation solutions and public health messaging that provides equitable protection to heat-vulnerable people exposed to high indoor temperatures.

The association of indoor heat exposure with diabetes and respiratory 9-1-1 calls through emergency medical dispatch and services documentation

BACKGROUND

People with pre-existing medical conditions, who spend a large proportion of their time indoors, are at risk of emergent morbidities from elevated indoor heat exposures. In this study, indoor heat of structures wherein exposed people received Grady Emergency Services based care in Atlanta, GA, U.S., was measured from May to September 2016.

METHOD

ology: In this case-control study, analyses were conducted to investigate the effect of indoor heat on the odds of 9-1-1 calls for diabetic (n = 90 cases) and separately, for respiratory (n = 126 cases), conditions versus heat-insensitive emergencies (n = 698 controls). Generalized Additive Models considered both linear and non-linear indoor heat and health outcome associations using thin-plate regression splines.

RESULTS

Hotter and more humid indoor conditions were non-linearly associated with an increasing likelihood of receiving emergency care for complications of diabetes and severe respiratory distress. Higher heat indices were associated with increased odds of a diabetes (odds ratio for change from 30 to 31 °C: 1.12, 95% CI: 1.08-1.16) or respiratory 9-1-1 medical call versus control (odds ratio for change from 34 to 35 °C: 1.18, 95% CI: 1.09-1.28) call. Both diabetic and respiratory distress patients were more likely to be African-American and/or have comorbidities.

CONCLUSIONS

In this study, the statistical association of indoor heat exposure with emergency morbidities (diabetic, respiratory) was demonstrated. The study also showcased the value and utility of data gathered by emergency medical dispatch and services from inaccessible private indoor sources (i.e., domiciles) for environmental health.

American Medical Society for Sports Medicine Position Statement on the Care of the Athlete and Athletic Person With Diabetes

ABSTRACT

The American Medical Society for Sports Medicine (AMSSM) developed this position statement to assist physicians and other health professionals in managing athletes and active people with diabetes. The AMSSM selected the author panel through an application process to identify members with clinical and academic expertise in the care of active patients with diabetes. This article reviews the current knowledge and gaps regarding the benefits and risks of various types of exercise and management issues for athletes and physically active people with diabetes, including nutrition and rehabilitation issues. Resistance exercises seem to be beneficial for patients with type 1 diabetes, and the new medications for patients with type 2 diabetes generally do not need adjustment with exercise. In preparing this statement, the authors conducted an evidence review and received open comment from the AMSSM Board of Directors before finalizing the recommendations.

Iranian National Clinical Practice Guideline for Exercise in Patients with Diabetes

CONTEXT

Growing evidence highlights the importance of physical activity as a critical element for the prevention and control of diabetes. However, there is no clinical practice guideline focusing on the different aspects of exercise in patients with diabetes, especially for the Iranian population.

OBJECTIVE

We aimed to prepare and adopt a clinical practice guideline to provide well-defined, simple, and concise responses to certain questions related to physical activity and exercise in all patients with diabetes, including type 1, 2, and gestational diabetes mellitus (GDM).

EVIDENCE ACQUISITION

A multidisciplinary team of experts in various fields (sports medicine specialists, endocrinologists, and cardiologists) developed the guideline. This group did the task in four stages: (1) identifying and refining the subject area using 17 clinical questions; (2) appraising evidence through a systematic review of the literature; (3) extracting recommendations from evidence and grading them as A, B, C, or D based on the quality, quantity, and consistency of existing evidence; and (4) subjecting the guideline to external review and finally selecting the recommendations with high scores of appropriateness and agreement. The final version was evaluated and approved by the National Deputy for Curative Affairs - Ministry of Health and Medical Education and has also been endorsed by the Iran Endocrine Society (IES) and Iranian Association of Sports and Exercise Medicine (IASEM).

RESULTS

The guideline consists of 52 recommendations addressing 17 important questions concerning different aspects of exercise prescription in Iranian patients with diabetes.

CONCLUSIONS

The guideline provides evidence-based information that may help physicians to prescribe exercise for Iranian patients with diabetes safely and effectively.

Global warming, heat-related illnesses, and the dermatologist

Global warming, provoked by the greenhouse effect of high levels of atmospheric gases (most notably carbon dioxide and methane), directly threatens human health and survival. Individuals vary in their capacity to tolerate episodes of extreme heat. Because skin is the organ tasked with heat dissipation, it is important for dermatologists to be versed in the physiology of cutaneous heat dissipation and cognizant of clinical settings in which the skin’s thermoregulatory responses may be impaired. When the external temperature is lower than that of the skin, the skin releases internal heat through direct thermal exchange with the environment, a process that is aided by an expansion of cutaneous blood flow and eccrine sweating. Cooling through the evaporation of sweat is effective even when the external temperature exceeds that of skin. Many factors, including environmental and physiological (e.g., age and sex), and pathological (e.g., preexisting illnesses, disorders of eccrine function, and medications) considerations, affect the skin’s capacity to thermoregulate. Identification of individuals at increased risk for heat-related morbidity and mortality will become increasingly important in the care of patients.

Impacts of climate change on the public health of the Mediterranean Basin population - Current situation, projections, preparedness and adaptation

The Mediterranean Basin is undergoing a warming trend with longer and warmer summers, an increase in the frequency and the severity of heat waves, changes in precipitation patterns and a reduction in rainfall amounts. In this unique populated region, which is characterized by significant gaps in the socio-economic levels particularly between the North (Europe) and South (Africa), parallel with population growth and migration, increased water demand and forest fires risk - the vulnerability of the Mediterranean population to human health risks increases significantly. Indeed, climatic changes impact the health of the Mediterranean population directly through extreme heat, drought or storms, or indirectly by changes in water availability, food provision and quality, air pollution and other stressors. The main health effects are related to extreme weather events (including extreme temperatures and floods), changes in the distribution of climate-sensitive diseases and changes in environmental and social conditions. The poorer countries, particularly in North Africa and the Levant, are at highest risk. Climate change affects the vulnerable sectors of the region, including an increasingly older population, with a larger percentage of those with chronic diseases, as well as poor people, which are therefore more susceptible to the effects of extreme temperatures. For those populations, a better surveillance and control systems are especially needed. In view of the climatic projections and the vulnerability of Mediterranean countries, climate change mitigation and adaptation become ever more imperative. It is important that prevention Health Action Plans will be implemented, particularly in those countries that currently have no prevention plans. Most adaptation measures are "win-win situation" from a health perspective, including reducing air pollution or providing shading solutions. Additionally, Mediterranean countries need to enhance cross-border collaboration, as adaptation to many of the health risks requires collaboration across borders and also across the different parts of the basin.

Wilderness Medical Society Clinical Practice Guidelines for Diabetes Management

The Wilderness Medical Society convened an expert panel in 2018 to develop a set of evidence-based guidelines for the treatment of type 1 and 2 diabetes, as well as the recognition, prevention, and treatment of complications of diabetes in wilderness athletes. We present a review of the classifications, pathophysiology, and evidence-based guidelines for planning and preventive measures, as well as best practice recommendations for both routine and urgent therapeutic management of diabetes and glycemic complications. These recommendations are graded based on the quality of supporting evidence and balance between the benefits and risks or burdens for each recommendation.

The effect of time spent outdoors during summer on daily blood glucose and steps in women with type 2 diabetes

This study investigated changes in glycemic control following a small increase in time spent outdoors. Women participants with type 2 diabetes (N = 46) wore an iBUTTON temperature monitor and a pedometer for 1 week and recorded their morning fasting blood glucose (FBG) daily. They went about their normal activities for 2 days (baseline) and were asked to add 30 min of time outdoors during Days 3-7 (intervention). Linear mixed effects models were used to test whether morning FBG values were different on days following intervention versus baseline days, and whether steps and/or heat exposure changed. Results were stratified by indicators of good versus poor glycemic control prior to initiation of the study. On average, blood glucose was reduced by 6.1 mg/dL (95% CI - 11.5, - 0.6) on mornings after intervention days after adjusting for age, BMI, and ambient weather conditions. Participants in the poor glycemic control group (n = 16) experienced a 15.8 mg/dL decrease (95% CI - 27.1, - 4.5) in morning FBG on days following the intervention compared to a 1.6 mg/dL decrease (95%CI - 7.7, 4.5) for participants in the good glycemic control group (n = 30). Including daily steps or heat exposure did not attenuate the association between intervention and morning FBG. The present study suggests spending an additional 30 min outdoors may improve glycemic control; however, further examination with a larger sample over a longer duration and determination of mediators of this relationship is warranted.

Association between Heat Exposure and Hospitalization for Diabetes in Brazil during 2000-2015: A Nationwide Case-Crossover Study

BACKGROUND

Exposure to excessive heat, which will continue to increase with climate change, is associated with increased morbidity due to a range of noncommunicable diseases (NCDs). Whether this is true for diabetes is unknown.

OBJECTIVES

We aimed to quantify the relationship between heat exposure and risk of hospitalization due to diabetes in Brazil.

METHODS

Data on hospitalizations and weather conditions were collected from 1,814 cities during the hot seasons from 2000 to 2015. A time-stratified case-crossover design was used to quantify the association between hospitalization for diabetes and heat exposure. Region-specific odds ratios (ORs) were used to calculate the attributable fractions (AFs).

RESULTS

A total of 553,351 hospitalizations associated with diabetes were recorded during 2000-2015. Every 5°C increase in daily mean temperature was associated with 6% [OR=1.06; 95% confidence interval (CI): 1.04, 1.07] increase in hospitalization due to diabetes with lag 0-3 d. The association was greatest (OR=1.18; 95% CI: 1.13, 1.23) in those ≥80y of age, but did not vary by sex, and was generally consistent by region and type of diabetes. Assuming a causal association, we estimated that 7.3% (95% CI: 3.5, 10.9) of all hospitalizations due to diabetes in the hot season could be attributed to heat exposure during the study period.

DISCUSSION

Short-term heat exposure may increase the burden of diabetes-related hospitalization, especially among the very elderly. As global temperatures continue to rise, this burden is likely to increase. https://doi.org/10.1289/EHP5688.

Heatwaves and diabetes in Brisbane, Australia: a population-based retrospective cohort study

Background

Available data on the effects of heatwaves on hospitalizations for diabetes and the post-discharge status of diabetics are scarce. This study aimed to assess the effects of heatwaves on hospitalizations and post-discharge deaths for diabetes, and to identify the individual- and community-level characteristics [i.e. age, gender, Socio-economic Indexes for Areas (SEIFA), and normalized difference vegetation index (NDVI)] that modified heatwave effects.

Methods

Health data were extracted from a cohort study which included patients in Brisbane, Australia, who were hospitalized due to diabetes from 1st January 2005 to 31st December 2013, and died within 2 months after they were discharged. Data on community-level modifiers, including SEIFA and NDVI (i.e. urban vegetation), were obtained from Australian Bureau of Statistics and Australian Bureau of Meteorology, respectively. Case-crossover design was used to quantify the effects of heatwaves on hospitalizations and post-discharge deaths due to diabetes. Four heatwave definitions incorporating both intensity (i.e. 90th, 95th, 97th and 99th percentiles of mean temperature distribution) and duration (2 days), as well as excess heat factor (EHF), were used. A case-only design was adopted to identify the modifiers of heatwave effects.

Results

There were 10 542 hospitalizations for diabetes, and 513 patients died due to diabetes within 2 months after discharge. During low-intensity heatwave days (i.e. 90th percentile & 2 days), we did not observe a significant increase in hospitalizations for diabetes [9% at lag 0; 95% confidence interval (CI): –3%, 23%; P = 0.146], but we observed a significant increase in post-discharge deaths (46% at lag 2; 95% CI: 3%, 107%; P = 0.036). During middle-intensity heatwave days (i.e. 95th percentile & 2 days), hospitalizations for diabetes increased by 19% at lag 0 (95% CI: 2%, 39%; P = 0.026), and post-discharge deaths increased by 64% at lag 0 (95% CI: 6%, 154%; P = 0.027). During high-intensity heatwave days (i.e. 97th percentile & 2 days), hospitalizations for diabetes increased by 37% at lag 1 (95% CI: 11%, 69%; P = 0.004) and post-discharge deaths increased by 137% at lag 1 (95% CI: 39%, 303%; P = 0.002). When heatwave intensity increased to 99th percentile, we did not observe a significant increase in hospitalizations (–1% at lag 0; 95% CI: –38%, 59%; P = 0.870) or post-discharge deaths (79% at lag 0; 95% CI: –39%, 431%; P = 0.301). When we used EHF to define heatwaves, we observed significant increases of hospitalizations (7%; 95% CI: 1%, 15%; P = 0.039) and post-discharge deaths (68%, 95% CI: 10%, 158%; P = 0.017) during heatwave days, compared with non-heatwave days. Children and male diabetics were particularly vulnerable to heatwave effects, but we did not find any significant modification effect of SEIFA or NDVI on the associations of heatwaves with hospitalizations and post-discharge deaths due to diabetes.

Conclusion

Heatwaves may lead to hospitalizations of diabetics and their premature deaths. Heat-related diabetes burden in children may increase as climate warms and with increasing obesity rates in adolescents.

Assessing heatwave impacts on cause-specific emergency department visits in urban and rural communities of Queensland, Australia

BACKGROUND

Heatwave impact on morbidity of people in rural areas has rarely been assessed in prior studies, and recently published literature has documented heatwave impact on a wide spectrum of diseases, for example, ear and eye diseases.

OBJECTIVES

To examine the associations between heatwaves and cause-specific emergency department visits (EDVs) across eight communities in both urban and rural regions throughout Queensland, Australia.

METHODS

Daily data on EDVs, air pollution and climatic conditions during the 1st January 2013 to the 31st December 2015 were obtained from relevant government agencies. Heatwave was defined as ≥ 95th percentile of the mean temperature for three or more consecutive days in each community. A quasi-Poisson generalized additive model with a distributed lag non-linear model was used to assess the heatwave impacts on EDVs. Random effect meta-analysis was performed to investigate the effects of heatwaves on cause-specific EDVs across the urban and rural regions as well as the whole Queensland. The causes of EDVs investigated in this study were infectious and parasitic diseases (ICD code: A00-B99), endocrine, nutritional and metabolic diseases (E00-E90), mental and behavioural disorders (F00-F99), diseases of the nervous system (G00-G99), diseases of the ear and mastoid process (H60-H95), diseases of the circulatory system (I00-I99), diseases of the respiratory system (J00-J99), diseases of the skin and subcutaneous tissue (L00-L99), diseases of the musculoskeletal system and connective tissue (M00-M99), diseases of the genitourinary system (N00-N99), and injury, poisoning and certain other consequences of external causes (S00-T98).

RESULTS

The meta-analysis results showed that there were significant effects of heatwaves on total EDVs and a wide-spectrum of cause-specific EDVs. For example, EDVs for endocrine, nutritional and metabolic diseases (RR: 1.18, 95% CI: 1.04-1.34), diseases of the nervous system (RR: 1.09, 95% CI: 1.02-1.17), and diseases of the genitourinary system (RR: 1.05, 95% CI: 1.00-1.09) increased substantially during heatwave days. The effect of heatwaves on total EDVs was similar for rural (RR: 1.04, 95% CI: 1.01-1.07) and urban regions (RR: 1.04, 95% CI: 1.00-1.07).

CONCLUSIONS

A wide range of diseases were sensitive to heatwave impacts. Residents in urban and rural areas were all vulnerable to heatwave impacts, calling for heat adaptation measures to be undertaken in Queensland, Australia.

Vulnerability to heatwaves and implications for public health interventions - A scoping review

BACKGROUND

Heatwaves form a serious public health threat, especially for vulnerable groups. Interventions such as active outreach programs, exposure reduction measures and monitoring and mapping of at-risk groups are increasingly implemented across the world but little is known about their effect.

OBJECTIVES

To assess how vulnerable groups are identified and reached in heat health interventions, to understand the effectiveness and efficiency of those interventions, and to identify research gaps in existing literature.

METHODS

We performed a literature search in relevant scientific literature databases and searched with a four element search model for articles published from 1995 onward. We extracted data on intervention measures, target group and evaluation of effectiveness and efficiency.

RESULTS

We identified 23 eligible studies. Patterns exist in type of interventions 1) to detect and 2) to influence extrinsic and intrinsic risk and protective factors. Results showed several intervention barriers related to the variety and intersection of these factors, as well as the self-perception of vulnerable groups, and misconceptions and unfavorable attitudes towards intervention benefits. While modest indications for the evidence on the effectiveness of interventions were found, efficiency remains unclear.

DISCUSSION

Interventions entailed logical combinations of measures, subsumed as packages. Evidence for effective and efficient intervention is limited by the difficulty to determine effects and because single measures are mutually dependent. Interventions prioritized promoting behavioral change and were based on behavioral assumptions that remain untested and mechanisms not worked out explicitly.

CONCLUSIONS

Multifaceted efforts are needed to tailor interventions, compiled in heat health warning systems and action plans for exposure reduction and protection of vulnerable populations, to fit the social, economic and geographical context. Besides adequately addressing relevant risk and protective factors, the challenge is to integrate perspectives of vulnerable groups. Future research should focus on intervention barriers and improving the methods of effectiveness and efficiency evaluation.

Towards establishing evidence-based guidelines on maximum indoor temperatures during hot weather in temperate continental climates

Rising environmental temperatures represent a major threat to human health. The activation of heat advisories using evidence-based thresholds for high-risk outdoor ambient temperatures have been shown to be an effective strategy to save lives during hot weather. However, although the relationship between weather and human health has been widely defined by outdoor temperature, corresponding increases in indoor temperature during heat events can also be harmful to health especially in vulnerable populations. In this review, we discuss our current understanding of the relationship between outdoor temperature and human health and examine how human health can also be adversely influenced by high indoor temperatures during heat events. Our assessment of the existing literature revealed a high degree of variability in what can be considered an acceptable indoor temperature because there are differences in how different groups of people may respond physiologically and behaviorally to the same living environment. Finally, we demonstrate that both non-physiological (e.g., geographical location, urban density, building design) and physiological (e.g., sex, age, fitness, state of health) factors must be considered when defining an indoor temperature threshold for preserving human health in a warming global climate.

Development of a Diabetes Mellitus Knowledge Resource for Clinical Decision Support Assisting Primary Care Physicians With Work-Related Issues

OBJECTIVE

The aim of this study was to describe the process by which a group of subject matter experts (SMEs) in the area of occupational health and primary care developed a clinical decision support (CDS) tool addressing work-related issues, which are important in the care of patients with diabetes mellitus (DM). The CDS is intended for primary care clinicians caring for employed adults with DM.

METHODS

The SME's selected guidelines for the management of DM in working adults, reviewed pertinent literature, and developed specific recommendations for action in the clinical setting.

RESULTS

Multiple factors at work may adversely affect DM management. Clinicians can support working patients through education and care strategies to improve control.

CONCLUSION

Improved recognition of factors at work that can have an impact on DM care provides opportunities for improved management of DM among working adults.

The effect of ambient temperature on type-2-diabetes: case-crossover analysis of 4+ million GP consultations across England

BACKGROUND

Given the double jeopardy of global increases in rates of obesity and climate change, it is increasingly important to recognise the dangers posed to diabetic patients during periods of extreme weather. We aimed to characterise the associations between ambient temperature and general medical practitioner consultations made by a cohort of type-2 diabetic patients. Evidence on the effects of temperature variation in the primary care setting is currently limited.

METHODS

Case-crossover analysis of 4,474,943 consultations in England during 2012-2014, linked to localised temperature at place of residence for each patient. Conditional logistic regression was used to assess associations between each temperature-related consultation and control days matched on day-of-week.

RESULTS

There was an increased odds of seeking medical consultation associated with high temperatures: Odds ratio (OR) = 1.097 (95% confidence interval = 1.041, 1.156) per 1 °C increase above 22 °C. Odds during low temperatures below 0 °C were also significantly raised: OR = 1.024 (1.019, 1.030). Heat-related consultations were particularly high among diabetics with cardiovascular comorbidities: OR = 1.171 (1.031, 1.331), but there was no heightened risk with renal failure or neuropathy comorbidities. Surprisingly, lower odds of heat-related consultation were associated with the use of diuretics, anticholinergics, antipsychotics or antidepressants compared to non-use, especially among those with cardiovascular comorbidities, although differences were not statistically significant.

CONCLUSIONS

Type-2 diabetic patients are at increased odds of medical consultation during days of temperature extremes, especially during hot weather. The common assumption that certain medication use heightens the risk of heat illness was not borne-out by our study on diabetics in a primary care setting and such advice may need to be reconsidered in heat protection plans.

The impact of maternal factors on the association between temperature and preterm delivery

BACKGROUND

Few studies have examined maternal modifiers of temperature and adverse birth outcomes because of lack of data. We assessed the relationship between apparent temperature, preterm delivery (PTD) and maternal demographics, medical and mental health conditions, and behaviors.

METHODS

A time-stratified case-crossover analysis was conducted using 14,466 women who had a PTD (20 to less than 37 gestational weeks) from 1995 to 2009 using medical records from a large health maintenance organization in Northern California. Effect modifiers considered by stratification included several maternal factors: age, race/ethnicity, depression, hypertension, diabetes, smoking, alcohol use, pre-pregnancy body mass index, and Medicaid status. Apparent temperature data for women who had a monitor located within 20km of their residential zip codes were included. All analyses were stratified by warm (May 1 through October 31) and cold (November 1 through April 30) seasons.

RESULTS

For every 10°F (5.6°C) increase in average cumulative weekly apparent temperature (lag06), a greater risk was observed for births occurring during the warm season (11.63%; 95% CI: 4.08, 19.72%) compared to the cold season (6.18%; -2.96, 16.18%), especially for mothers who were younger, Black, Hispanic, underweight, smoked or consumed alcohol during pregnancy, or had pre-existing /gestational hypertension, diabetes, or pre-eclampsia.

CONCLUSIONS

Our findings suggest that warmer apparent temperatures exacerbate the risk of PTD, particularly for subgroups of more vulnerable women.

Obese type 2 diabetics have a blunted hypotensive response to acute hyperthermia therapy that does not affect the perception of thermal stress or physiological strain compared to healthy adults

PURPOSE

The objective of this study was to test the hypothesis that a hyperthermia-hypotensive challenge via whole body hot water immersion would alter the perception of hyperthermia and physiological strain in obese type 2 diabetics (T2DM) compared to healthy non-obese (HC) individuals. Additionally, we hypothesize that the mechanisms would be attributed to impaired blood pressure adjustments and afferent signals (via changes in internal and mean skin temperatures).

METHODS

In random order, eleven obese T2DM (50±12y, 45±7% fat mass, 7.5±1.8% HbA1c) and nine similar aged (41±14y, P>0.05) HC non-obese (33±8% fat mass, P<0.01) non-diabetic (5.3±0.4% HbA1c, P<0.01) underwent a 60min bout of whole body passive hyperthermia followed by 60min of recovery or a 2h resting control condition. The perception of thermal sensation (TS, scale range: 1-13), calculated physiological strain (PSI), internal (Tre, rectal) and mean skin (Tsk) temperatures, heart rate (HR) and blood pressures (BP) were the primary dependent variables.

RESULTS

Hyperthermia similarly increased Tre by 1.4±0.4°C, Tsk by 6.5±0.8°C and HR by 34±8bpm in both groups (P>0.5). Hyperthermia reduced diastolic BP (27% in T2DM and 33% in HC, P<0.05) and mean arterial BP (reduced by 15% in T2DM and by 19% in HC) relative to control conditions (P<0.05). The reduction of mean arterial BP area under the curve was attenuated in T2DM (12%) compared to HC (30%) (group×condition, P<0.01). TS and PSI during hyperthermia were not different between groups. Pearson product correlation reported strong correlations (r=0.69-0.89) with Tre and Tsk with TS in both populations. The linear stepwise regression analysis revealed similar relative contributions for Tre (~60%) and Tsk (~40%) on TS for both groups.

CONCLUSIONS

These data indicate that obese T2DM with moderate metabolic control have an attenuated hyperthermia-hypotensive response that does not affect TS and PSI. This also may suggest behavioral thermoregulation is intact in this study group.

Cerebral Vascular Control and Metabolism in Heat Stress

This review provides an in-depth update on the impact of heat stress on cerebrovascular functioning. The regulation of cerebral temperature, blood flow, and metabolism are discussed. We further provide an overview of vascular permeability, the neurocognitive changes, and the key clinical implications and pathologies known to confound cerebral functioning during hyperthermia. A reduction in cerebral blood flow (CBF), derived primarily from a respiratory-induced alkalosis, underscores the cerebrovascular changes to hyperthermia. Arterial pressures may also become compromised because of reduced peripheral resistance secondary to skin vasodilatation. Therefore, when hyperthermia is combined with conditions that increase cardiovascular strain, for example, orthostasis or dehydration, the inability to preserve cerebral perfusion pressure further reduces CBF. A reduced cerebral perfusion pressure is in turn the primary mechanism for impaired tolerance to orthostatic challenges. Any reduction in CBF attenuates the brain's convective heat loss, while the hyperthermic-induced increase in metabolic rate increases the cerebral heat gain. This paradoxical uncoupling of CBF to metabolism increases brain temperature, and potentiates a condition whereby cerebral oxygenation may be compromised. With levels of experimentally viable passive hyperthermia (up to 39.5-40.0 °C core temperature), the associated reduction in CBF (∼ 30%) and increase in cerebral metabolic demand (∼ 10%) is likely compensated by increases in cerebral oxygen extraction. However, severe increases in whole-body and brain temperature may increase blood-brain barrier permeability, potentially leading to cerebral vasogenic edema. The cerebrovascular challenges associated with hyperthermia are of paramount importance for populations with compromised thermoregulatory control--for example, spinal cord injury, elderly, and those with preexisting cardiovascular diseases.

Body temperature regulation in diabetes

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

Predictive Factors for Hospitalization of Patients with Heat Illness in Yamaguchi, Japan

The objective of the study was to investigate the predictive factors for the hospitalization of patients who presented with mild to moderate heat illness at an emergency department. We conducted a retrospective survey of hospitals with an emergency department in Yamaguchi Prefecture, Japan. The survey questionnaire entries included patient age, sex, use of an ambulance, vital signs, blood examination conducted at the emergency department, the length of hospitalization, and outcome. We analyzed the predictive factors for hospitalization in patients with heat illness. A total of 127 patients were analyzed. Of these, 49 (37%) were admitted, with 59% discharged on the day following admission. In univariate analysis, the following inpatient characteristics were predictive for hospitalization: old age, low Glasgow Coma Scale score, elevated body temperature, increased serum C-reactive protein, and increased blood urea nitrogen. In logistic regression multivariate analysis, the following were predictive factors for hospitalization: age of ≥ 65 years (odds ratio (OR) 4.91; 95% confidence interval (CI) 1.42–17.00), body temperature (OR 1.97; 95% CI 1.14–3.41), Glasgow Coma Scale (OR 0.40; 95% CI 0.16–0.98), and creatinine (OR 2.92; 95% CI 1.23–6.94). The results suggest that the elderly with hyperthermia, disturbance of consciousness, and elevated serum creatinine have an increased risk for hospitalization with heat illness.

Lifestyle intervention: nutrition therapy and physical activity

Diabetes now affects more than 29 million Americans, and more than 9 million of these people do not know they have diabetes. In adults, type 2 diabetes accounts for about 90% to 95% of all diagnosed cases of diabetes and is the focus of this article. Lifestyle intervention is part of the initial treatment as well as the ongoing management of type 2 diabetes. Lifestyle intervention encompasses a healthful eating plan, physical activity, and often medication to assist in achievement of glucose, lipid, and blood pressure goals. Patient education and self-care practices are also important aspects of disease management.

Thermometry, calorimetry, and mean body temperature during heat stress

Heat balance in humans is maintained at near constant levels through the adjustment of physiological mechanisms that attain a balance between the heat produced within the body and the heat lost to the environment. Heat balance is easily disturbed during changes in metabolic heat production due to physical activity and/or exposure to a warmer environment. Under such conditions, elevations of skin blood flow and sweating occur via a hypothalamic negative feedback loop to maintain an enhanced rate of dry and evaporative heat loss. Body heat storage and changes in core temperature are a direct result of a thermal imbalance between the rate of heat production and the rate of total heat dissipation to the surrounding environment. The derivation of the change in body heat content is of fundamental importance to the physiologist assessing the exposure of the human body to environmental conditions that result in thermal imbalance. It is generally accepted that the concurrent measurement of the total heat generated by the body and the total heat dissipated to the ambient environment is the most accurate means whereby the change in body heat content can be attained. However, in the absence of calorimetric methods, thermometry is often used to estimate the change in body heat content. This review examines heat exchange during challenges to heat balance associated with progressive elevations in environmental heat load and metabolic rate during exercise. Further, we evaluate the physiological responses associated with heat stress and discuss the thermal and nonthermal influences on the body's ability to dissipate heat from a heat balance perspective.