1
|
Crank PJ, O'Lenick CR, Baniassadi A, Sailor DJ, Wilhelmi O, Hayden M. Sociodemographic Determinants of Extreme Heat and Ozone Risk Among Older Adults in 3 Sun Belt Cities. J Gerontol A Biol Sci Med Sci 2024; 79:glae164. [PMID: 39073887 DOI: 10.1093/gerona/glae164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Indexed: 07/31/2024] Open
Abstract
BACKGROUND Vulnerable populations across the United States are frequently exposed to extreme heat, which is becoming more intense due to a combination of climate change and urban-induced warming. Extreme heat can be particularly detrimental to the health and well-being of older citizens when it is combined with ozone. Although population-based studies have demonstrated associations between ozone, extreme heat, and human health, few studies focused on the role of social and behavioral factors that increase indoor risk and exposure among older adults. METHODS We conducted a household survey that aimed to understand how older adults are affected by extreme heat and ozone pollution inside and outside of their homes across Houston, Phoenix, and Los Angeles. We examine contributing factors to the risk of self-reported health effects using a generalized linear mixed-effects regression model of telephone survey data of 909 older adults in 2017. RESULTS We found an increased occurrence of self-reported symptoms for extreme heat with preexisting respiratory health conditions and a lack of air conditioning access; self-reported ozone symptoms were more likely with preexisting respiratory health conditions. The risk of heat-related symptoms was slightly higher in Los Angeles than Houston and Phoenix. We found several demographic, housing, and behavioral characteristics that influenced the risk of heat- and ozone-related symptoms. CONCLUSIONS The increased risk among older adults based on specific social and behavioral factors identified in this study can inform public health policy and help cities tailor their heat and ozone response plans to the specific needs of this vulnerable population.
Collapse
Affiliation(s)
- Peter J Crank
- Department of Geography and Environmental Management, University of Waterloo, Waterloo, Ontario, Canada
| | - Cassandra R O'Lenick
- Center for Environmental Medicine, Asthma and Lung Biology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Amir Baniassadi
- Department of Medicine, Harvard Medical School, Boston, Massachusetts, USA
- Marcus Institute for Aging Research, Hebrew SeniorLife, Boston, Massachusetts, USA
| | - David J Sailor
- Urban Climate Research Center, Arizona State University, Tempe, Arizona, USA
- School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, Arizona, USA
| | - Olga Wilhelmi
- NSF National Center for Atmospheric Research, Boulder, Colorado, USA
| | - Mary Hayden
- Lyda Hill Institute for Human Resilience, University of Colorado-Colorado Springs, Colorado Springs, Colorado, USA
| |
Collapse
|
2
|
Kenny GP, Tetzlaff EJ, Journeay WS, Henderson SB, O’Connor FK. Indoor overheating: A review of vulnerabilities, causes, and strategies to prevent adverse human health outcomes during extreme heat events. Temperature (Austin) 2024; 11:203-246. [PMID: 39193048 PMCID: PMC11346563 DOI: 10.1080/23328940.2024.2361223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 05/07/2024] [Accepted: 05/20/2024] [Indexed: 08/29/2024] Open
Abstract
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.
Collapse
Affiliation(s)
- Glen P. Kenny
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
- Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | - Emily J. Tetzlaff
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
| | - W. Shane Journeay
- Departments of Medicine and Community Health and Epidemiology, Dalhousie Medicine New Brunswick and Dalhousie University, Saint John, NB, Canada
- Department of Medicine, Division of Physical Medicine and Rehabilitation, University of Toronto, Toronto, ON, Canada
- Department of Rehabilitative Care, Providence Healthcare-Unity Health Toronto, Toronto, ON, Canada
| | - Sarah B. Henderson
- Environmental Health Services, British Columbia Centre for Disease Control, Vancouver, BC, Canada
- National Collaborating Centre for Environmental Health, Vancouver, BC, Canada
| | - Fergus K. O’Connor
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
| |
Collapse
|
3
|
Meade RD, Notley SR, Kirby NV, Kenny GP. A critical review of the effectiveness of electric fans as a personal cooling intervention in hot weather and heatwaves. Lancet Planet Health 2024; 8:e256-e269. [PMID: 38580427 DOI: 10.1016/s2542-5196(24)00030-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 01/26/2024] [Accepted: 02/22/2024] [Indexed: 04/07/2024]
Abstract
Health agencies worldwide have historically cautioned that electric fans accelerate body-heat gain during hot weather and heatwaves (typically in air temperatures ≥35°C). However, guidance published since 2021 has suggested that fans can still cool the body in air temperatures up to 40°C by facilitating sweat evaporation, and therefore are an inexpensive yet sustainable alternative to air conditioning. In a critical analysis of the reports cited to support this claim, we found that although fan use improves sweat evaporation, these benefits are of insufficient magnitude to exert meaningful reductions in body core temperature in air temperatures exceeding 35°C. Health agencies should continue to advise against fan use in air temperatures higher than 35°C, especially for people with compromised sweating capacity (eg, adults aged 65 years or older). Improving access to ambient cooling strategies (eg, air conditioning or evaporative coolers) and minimising their economic and environmental costs through policy initiatives, efficient cooling technology, and combined use of low-cost personal interventions (eg, skin wetting or fan use) are crucial for climate adaptation.
Collapse
Affiliation(s)
- Robert D Meade
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada; Harvard T H Chan School of Public Health, Harvard University, Boston, MA, USA
| | - Sean R Notley
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
| | - Nathalie V Kirby
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
| | - Glen P Kenny
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada; Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.
| |
Collapse
|
4
|
Meade RD, Akerman AP, Notley SR, Kirby NV, Sigal RJ, Kenny GP. Effects of Daylong Exposure to Indoor Overheating on Thermal and Cardiovascular Strain in Older Adults: A Randomized Crossover Trial. ENVIRONMENTAL HEALTH PERSPECTIVES 2024; 132:27003. [PMID: 38329752 PMCID: PMC10852046 DOI: 10.1289/ehp13159] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 11/29/2023] [Accepted: 12/22/2023] [Indexed: 02/09/2024]
Abstract
BACKGROUND Health agencies recommend that homes of heat-vulnerable occupants (e.g., older adults) be maintained below 24-28°C to prevent heat-related mortality and morbidity. However, there is limited experimental evidence to support these recommendations. OBJECTIVE To aid in the development of evidence-based guidance on safe indoor temperatures for temperate continental climates, we evaluated surrogate physiological outcomes linked with heat-related mortality and morbidity in older adults during simulated indoor overheating. METHODS Sixteen older adults [six women; median age: 72 y, interquartile range (IQR): 70-73 y; body mass index: 24.6 ( IQR : 22.1 - 27.0 ) kg / m 2 ] from the Ottawa, Ontario, Canada, region (warm summer continental climate) completed four randomized, 8-h exposures to conditions experienced indoors during hot weather in continental climates (e.g., Ontario, Canada; 64 participant exposures). Ambient conditions simulated an air-conditioned environment (22°C; control), proposed indoor temperature upper limits (26°C), and temperatures experienced in homes without air-conditioning (31°C and 36°C). Core temperature (rectal) was monitored as the primary outcome; based on previous recommendations, between-condition differences > 0.3 ° C were considered clinically meaningful. RESULTS Compared with 22°C, core temperature was elevated to a meaningful extent in 31°C [+ 0 . 7 ° C ; 95% confidence interval (CI): 0.5, 0.8] and 36°C (+ 0 . 9 ° C ; 95% CI: 0.8, 1.1), but not 26°C (+ 0 . 2 ° C , 95% CI: 0.0, 0.3). Increasing ambient temperatures were also associated with elevated heart rate and reduced arterial blood pressure and heart rate variability at rest, as well as progressive impairments in cardiac and blood pressure responses to standing from supine. DISCUSSION Core temperature and cardiovascular strain were not appreciably altered following 8-h exposure to 26°C but increased progressively in conditions above this threshold. These data support proposals for the establishment of a 26°C indoor temperature upper limit for protecting vulnerable occupants residing in temperate continental climates from indoor overheating. https://doi.org/10.1289/EHP13159.
Collapse
Affiliation(s)
- Robert D. Meade
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
- Harvard T.H. Chan School of Public Health, Harvard University, Boston, Massachusetts, USA
| | - Ashley P. Akerman
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Sean R. Notley
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Nathalie V. Kirby
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
| | - Ronald J. Sigal
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
- Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Cardiac Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
| | - Glen P. Kenny
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada
- Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
| |
Collapse
|
5
|
Bach AJE, Cunningham SJK, Morris NR, Xu Z, Rutherford S, Binnewies S, Meade RD. Experimental research in environmentally induced hyperthermic older persons: A systematic quantitative literature review mapping the available evidence. Temperature (Austin) 2024; 11:4-26. [PMID: 38567267 PMCID: PMC7615797 DOI: 10.1080/23328940.2023.2242062] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 07/21/2023] [Indexed: 04/04/2024] Open
Abstract
The heat-related health burden is expected to persist and worsen in the coming years due to an aging global population and climate change. Defining the breadth and depth of our understanding of age-related changes in thermoregulation can identify underlying causes and strategies to protect vulnerable individuals from heat. We conducted the first systematic quantitative literature review to provide context to the historical experimental research of healthy older adults - compared to younger adults or unhealthy age matched cases - during exogenous heat strain, focusing on factors that influence thermoregulatory function (e.g. co-morbidities). We identified 4,455 articles, with 147 meeting eligibility criteria. Most studies were conducted in the US (39%), Canada (29%), or Japan (12%), with 71% of the 3,411 participants being male. About 71% of the studies compared younger and older adults, while 34% compared two groups of older adults with and without factors influencing thermoregulation. Key factors included age combined with another factor (23%), underlying biological mechanisms (18%), age independently (15%), influencing health conditions (15%), adaptation potential (12%), environmental conditions (9%), and therapeutic/pharmacological interventions (7%). Our results suggest that controlled experimental research should focus on the age-related changes in thermoregulation in the very old, females, those with overlooked chronic heat-sensitive health conditions (e.g. pulmonary, renal, mental disorders), the impact of multimorbidity, prolonged and cumulative effects of extreme heat, evidence-based policy of control measures (e.g. personal cooling strategies), pharmaceutical interactions, and interventions stimulating protective physiological adaptation. These controlled studies will inform the directions and use of limited resources in ecologically valid fieldwork studies.
Collapse
Affiliation(s)
- Aaron J. E. Bach
- School of Medicine and Dentistry, Griffith University, Gold Coast, QLD, Australia
- Cities Research Institute, Griffith University, Gold Coast, QLD, Australia
| | - Sarah J. K. Cunningham
- School of Medicine and Dentistry, Griffith University, Gold Coast, QLD, Australia
- Cities Research Institute, Griffith University, Gold Coast, QLD, Australia
| | - Norman R. Morris
- School of Health Sciences and Social Work, Griffith University, Gold Coast, QLD, Australia
- Metro North Hospital and Health Service, The Prince Charles Hospital. Allied Health Research Collaborative, Brisbane, QLD, Australia
- Menzies Health Institute Queensland, Griffith University, Gold Coast, QLD, Australia
| | - Zhiwei Xu
- School of Medicine and Dentistry, Griffith University, Gold Coast, QLD, Australia
- Cities Research Institute, Griffith University, Gold Coast, QLD, Australia
| | - Shannon Rutherford
- School of Medicine and Dentistry, Griffith University, Gold Coast, QLD, Australia
- Cities Research Institute, Griffith University, Gold Coast, QLD, Australia
| | - Sebastian Binnewies
- School of Information and Communication Technology, Griffith University, Gold Coast, QLD, Australia
| | - Robert D. Meade
- Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, ON, Canada
- Harvard T.H. Chan School of Public Health, Harvard University, Boston, MA, USA
| |
Collapse
|
6
|
Chen CH, Lin WY, Lee KY, Sun WJ, Huang LY, Guo YLL. Adaptation behaviors modify the effects of body fat on heat-related symptoms among Taiwanese elderly. Int J Hyg Environ Health 2024; 255:114296. [PMID: 37979230 DOI: 10.1016/j.ijheh.2023.114296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 11/07/2023] [Accepted: 11/09/2023] [Indexed: 11/20/2023]
Abstract
BACKGROUND The aging process increases body fat and susceptibility to heat-related illnesses. The relationship between body composition and symptoms associated with exposure to extreme heat among the elderly is unclear. Additionally, the influence of individual adaptive behaviors in mitigating these risks has not been adequately explored. OBJECTIVES This study aimed to evaluate the association between body composition and heat-related symptoms as well as the potential modifying effects of heat adaptation behavior. METHODS The body composition of elderly individuals was measured using bioelectrical impedance analysis. Face-to-face interviews were conducted a year later to determine the heat-related symptoms and adaptive behaviors practiced for the extremely hot days of the previous year. The association between body composition indices and the presence of more than two symptoms was assessed using logistic regression analysis, while stratified analysis and interaction term in models were used to evaluate the effect modifications of adaptive behaviors. RESULTS Of the 859 participants, 16% reported more than two heat-related symptoms. Increased body fat mass index (fat mass in kg/squared height in meters) was associated with an elevated risk of more heat-related symptoms (odds ratio 1.11, 95% confidence interval 1.02-1.20). Each combination of staying indoors, using an umbrella and hat, and using air conditioning at noon reduced the risk association between body fat and symptoms. For females, a combination of reducing physical activity and staying indoors provided similar protective effect. Surprisingly, bathing more frequently in hot weather with heated instead of non-heated water augmented the risk correlation. Neither fan usage nor window opening displayed protective effects. CONCLUSIONS Elevated body fat levels, indicative of obesity, corresponded with an increased risk of heat-related symptoms. Integrating multiple adaptive behaviors can diminish the negative health impact of body fat on heat-induced symptoms. However, certain commonly adopted practices might not confer expected benefits.
Collapse
Affiliation(s)
- Chi-Hsien Chen
- Department of Environmental and Occupational Medicine, National Taiwan University (NTU) College of Medicine and NTU Hospital, Taipei, Taiwan
| | - Wen-Yi Lin
- Department of Occupational Medicine, Health Management Center, Kaohsiung Municipal Siaogang Hospital, Kaohsiung Medical University, Taiwan; Research Center for Environmental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Kang-Yun Lee
- Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan; Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Wen-Jung Sun
- Department of Community Medicine, Center of R/D in Community Based Palliative Care, Holistic Mental Health Center, Taipei City Hospital, Taipei, Taiwan; Family Medicine Division, Taipei City Hospital Zhongxing Branch, Taipei, Taiwan
| | - Li-Ying Huang
- School of Medicine, College of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan; Division of Endocrinology and Metabolism, Department of Internal Medicine, and Department of Medical Education, Fu Jen Catholic University Hospital, New Taipei City, Taiwan
| | - Yue-Liang Leon Guo
- Department of Environmental and Occupational Medicine, National Taiwan University (NTU) College of Medicine and NTU Hospital, Taipei, Taiwan; National Institute of Environmental Sciences, National Health Research Institutes, Miaoli County, Taiwan; Institute of Environmental and Occupational Health Sciences, National Taiwan University, Taipei, 100, Taiwan.
| |
Collapse
|
7
|
Deshayes TA, Pancrate T, Goulet EDB. Effect of electric fan use in isolation or combined with ice slurry/cold water ingestion and lower-leg immersion in young men during intermittent physical activity in hot-humid conditions. Appl Physiol Nutr Metab 2023; 48:851-862. [PMID: 37698186 DOI: 10.1139/apnm-2023-0013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/13/2023]
Abstract
Using a randomized crossover protocol, 10 young men completed four 180 min exposures (38 °C, 60% relative humidity), alternating between 30 min of walking and 30 min of sitting where fluid or ice slurry were served. Participants underwent four trials: (i) 5 mL·kg body mass-1 of 20 °C water (CON); (ii) 5 mL·kg body mass-1 of 20 °C water + fan at 4 m·s-1 (FAN); (iii) fan + 3 mL·kg body mass-1 of ice slurry + 2 mL·kg body mass-1 of 4 °C water (FAN + ISCW); and (iv) FAN + ISCW + lower-leg immersion in 20 °C water (FAN + ISCW + LLI). Sweat and body mass losses were higher with FAN than CON, FAN + ISCW, and FAN + ISCW + LLI. Mean and peak changes in Δrectal temperature, heart rate, and perceived heat and thirst from baseline were not statistically and practically different between FAN and CON. FAN + ISCW + LLI decreased sweat loss compared with FAN + ISCW and mean and peak changes in Δrectal temperature, heart rate, and perceived thirst compared with CON. FAN + ISCW + LLI also attenuated the changes in Δrectal temperature (peak) and thirst (mean and peak) compared with FAN. In conclusion, FAN slightly exacerbates fluid loss but does not attenuate the changes in Δrectal temperature, heart rate, and perceived heat and thirst during intermittent physical activity in hot-humid conditions. However, coupling ISCW or ISCW + LLI with the use of a fan attenuates the increase in these outcomes compared with no intervention and to a greater extent for rectal temperature and thirst when fan is coupled with ISCW + LLI than when it is used in isolation.
Collapse
Affiliation(s)
- Thomas A Deshayes
- Faculty of physical activity sciences, University of Sherbrooke, Sherbrooke, QC J1K 2R1, Canada
- Research Center on Aging, University of Sherbrooke, Sherbrooke, QC J1H 4C4, Canada
| | - Timothée Pancrate
- Faculty of physical activity sciences, University of Sherbrooke, Sherbrooke, QC J1K 2R1, Canada
| | - Eric D B Goulet
- Faculty of physical activity sciences, University of Sherbrooke, Sherbrooke, QC J1K 2R1, Canada
- Research Center on Aging, University of Sherbrooke, Sherbrooke, QC J1H 4C4, Canada
| |
Collapse
|
8
|
Parsons LA, Lo F, Ward A, Shindell D, Raman SR. Higher Temperatures in Socially Vulnerable US Communities Increasingly Limit Safe Use of Electric Fans for Cooling. GEOHEALTH 2023; 7:e2023GH000809. [PMID: 37577109 PMCID: PMC10413955 DOI: 10.1029/2023gh000809] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 05/09/2023] [Accepted: 07/09/2023] [Indexed: 08/15/2023]
Abstract
As the globe warms, people will increasingly need affordable, safe methods to stay cool and minimize the worst health impacts of heat exposure. One of the cheapest cooling methods is electric fans. Recent research has recommended ambient air temperature thresholds for safe fan use in adults. Here we use hourly weather reanalysis data (1950-2021) to examine the temporal and spatial evolution of ambient climate conditions in the continental United States (CONUS) considered safe for fan use, focusing on high social vulnerability index (SVI) regions. We find that although most hours in the day are safe for fan use, there are regions that experience hundreds to thousands of hours per year that are too hot for safe fan use. Over the last several decades, the number of hours considered unsafe for fan use has increased across most of the CONUS (on average by ∼70%), with hotspots across the US West and South, suggesting that many individuals will increasingly need alternative cooling strategies. People living in high-SVI locations are 1.5-2 times more likely to experience hotter climate conditions than the overall US population. High-SVI locations also experience higher rates of warming that are approaching and exceeding important safety thresholds that relate to climate adaptation. These results highlight the need to direct additional resources to these communities for heat adaptive strategies.
Collapse
Affiliation(s)
- L. A. Parsons
- Nicholas School of the EnvironmentDuke UniversityDurhamNCUSA
- Global ScienceThe Nature ConservancyDurhamNCUSA
| | - F. Lo
- Environmental Defense FundNew York CityNYUSA
| | - A. Ward
- Nicholas Institute for Energy, Environment, and SustainabilityDuke UniversityDurhamNCUSA
| | - D. Shindell
- Nicholas School of the EnvironmentDuke UniversityDurhamNCUSA
| | - S. R. Raman
- Population Health SciencesDuke UniversityDurhamNCUSA
| |
Collapse
|
9
|
McKenna ZJ, Foster J, Atkins WC, Belval LN, Watso JC, Jarrard CP, Orth BD, Crandall CG. Age alters the thermoregulatory responses to extreme heat exposure with accompanying activities of daily living. J Appl Physiol (1985) 2023; 135:445-455. [PMID: 37410904 PMCID: PMC10538984 DOI: 10.1152/japplphysiol.00285.2023] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 06/15/2023] [Accepted: 06/27/2023] [Indexed: 07/08/2023] Open
Abstract
Older adults are at greater risk for heat-related morbidity and mortality, due in part to age-related reductions in heat dissipating capabilities. Previous studies investigating the impact of age on responses to heat stress used approaches that lack activities of daily living and therefore may not accurately depict the thermal/physiological strain that would occur during actual heatwaves. We sought to compare the responses of young (18-39 yr) and older (≥65 yr) adults exposed to two extreme heat simulations. Healthy young (n = 20) and older (n = 20) participants underwent two 3-h extreme heat exposures on different days: 1) DRY (47°C and 15% humidity) and 2) HUMID (41°C and 40% humidity). To mimic heat generation comparable with activities of daily living, participants performed 5-min bouts of light physical activity dispersed throughout the heat exposure. Measurements included core and skin temperatures, heart rate, blood pressure, local and whole body sweat rate, forearm blood flow, and perceptual responses. Δ core temperature (Young: 0.68 ± 0.27°C vs. Older: 1.37 ± 0.42°C; P < 0.001) and ending core temperature (Young: 37.81 ± 0.26°C vs. Older: 38.15 ± 0.43°C; P = 0.005) were greater in the older cohort during the DRY condition. Δ core temperature (Young: 0.58 ± 0.25°C vs. Older: 1.02 ± 0.32°C; P < 0.001), but not ending core temperature (Young: 37.67 ± 0.34°C vs. Older: 37.83 ± 0.35°C; P = 0.151), was higher in the older cohort during the HUMID condition. We demonstrated that older adults have diminished thermoregulatory responses to heat stress with accompanying activities of daily living. These findings corroborate previous reports and confirm epidemiological data showing that older adults are at a greater risk for hyperthermia.NEW & NOTEWORTHY Using an experimental model of extreme heat exposure that incorporates brief periods of light physical activity to simulate activities of daily living, the extent of thermal strain reported herein more accurately represents what would occur during actual heatwave conditions. Despite matching metabolic heat generation and environmental conditions, we show that older adults have augmented core temperature responses, likely due to age-related reductions in heat dissipating mechanisms.
Collapse
Affiliation(s)
- Zachary J McKenna
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Josh Foster
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Whitley C Atkins
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Luke N Belval
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Joseph C Watso
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Caitlin P Jarrard
- Cardiovascular and Applied Physiology Laboratory, Department of Nutrition and Integrative Physiology, Florida State University, Tallahassee, Florida, United States
| | - Bonnie D Orth
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
| | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| |
Collapse
|
10
|
Tokizawa K. Effects of wetted inner clothing on thermal strain in young and older males while wearing ventilation garments. Front Physiol 2023; 14:1122504. [PMID: 36909241 PMCID: PMC9992724 DOI: 10.3389/fphys.2023.1122504] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 02/13/2023] [Indexed: 02/24/2023] Open
Abstract
The present study examined the effect of wearing a water-soaked inner t-shirt with a ventilation garment on thermal and cardiovascular strain in eight young (26 ± 4 years) and eight older (67 ± 3 years) men undertaking moderate-intensity work (metabolic rate: 200-230 W m-2) in a hot environment (37°C, 50% RH, 2.8 kPa). While intermittent walking in hot conditions for 60 min, as a control (CON), the subject wore a dry inner t-shirt (long-sleeved) without fanning of a ventilation jacket (single-layered cotton, 0.21 clo). On separate days, under a fanned ventilation jacket, the subject wore a dry inner t-shirt (DRY) or an inner t-shirt soaked with 350 mL of tap water (WET). In the young group, increases in rectal temperature from pre-exercise baseline in the WET trial (0.7°C ± 0.2°C) were lower than in the CON (1.3°C ± 0.3°C) and DRY (1.1°C ± 0.2°C) (both p < 0.05) trials during exercise in hot conditions. In the older group, the increases were also attenuated in WET (0.7°C ± 0.4°C) compared with CON (1.3°C ± 0.4°C) and DRY (1.1°C ± 0.4°C) (both p < 0.05) without differences between age groups. Heart rate and whole-body sweat loss were lowest in the WET, followed by DRY, and then CON conditions in both groups (all p < 0.05). These findings demonstrate that wearing a water-soaked inner t-shirt while using a ventilation garment is an effective and practical cooling strategy to mitigate thermal and cardiovascular strains in young and older individuals during moderate-intensity work in hot conditions.
Collapse
Affiliation(s)
- Ken Tokizawa
- National Institute of Occupational Safety and Health, Tokyo, Japan
| |
Collapse
|
11
|
Extreme Heat and Cardiovascular Health: What a Cardiovascular Health Professional Should Know. Can J Cardiol 2021; 37:1828-1836. [PMID: 34802857 DOI: 10.1016/j.cjca.2021.08.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 07/23/2021] [Accepted: 08/09/2021] [Indexed: 01/22/2023] Open
Abstract
As global temperatures continue to rise, extreme heat events are becoming more frequent and intense. Extreme heat affects cardiovascular health as it is associated with a greater risk of adverse cardiovascular events, especially for adults with preexisting cardiovascular diseases. Nonetheless, the pathophysiology underlying the association between extreme heat and cardiovascular risk remains understudied. Furthermore, specific recommendations to mitigate the effects of extreme heat on cardiovascular health remain limited to guide clinical practice within the context of a warming climate. The overall objective of this review article is to raise awareness that extreme heat poses a risk for cardiovascular health. Specifically, the review discusses why cardiovascular healthcare professionals should care about extreme heat, how extreme heat affects cardiovascular health, and recommendations to minimise the cardiovascular consequences of extreme heat. Future research directions are also provided to further our understating of the cardiovascular health consequences of extreme heat. A better awareness and understanding of the cardiovascular consequences of extreme heat will help cardiovascular health professionals assess the risk and optimise the care of their patients exposed to an increasingly warm climate.
Collapse
|
12
|
Vecellio DJ, Bardenhagen EK, Lerman B, Brown RD. The role of outdoor microclimatic features at long-term care facilities in advancing the health of its residents: An integrative review and future strategies. ENVIRONMENTAL RESEARCH 2021; 201:111583. [PMID: 34192557 DOI: 10.1016/j.envres.2021.111583] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 05/18/2021] [Accepted: 06/21/2021] [Indexed: 06/13/2023]
Abstract
Projections show that Earth's climate will continue to warm concurrent with increases in the percentage of the world's elderly population. With an understanding that the body's resilience to the heat degrades as it ages, these coupled phenomena point to serious concerns of heat-related mortality in growing elderly populations. As many of the people in this age cohort choose to live in managed long-term care facilities, it's imperative that outdoor spaces of these communities be made thermally comfortable so that connections with nature and the promotion of non-sedentary activities are maintained. Studies have shown that simply being outside has a positive impact on a broad range of the psychosocial well-being of older adults. However, these spaces must be designed to afford accessibility, safety, and aesthetically pleasing experiences so that they are taken full advantage of. Here, we employ an integrative review to link ideas from the disciplines of climate science, health and physiology, and landscape architecture to explain the connections between heat, increased morbidity and mortality in aging adults, existing gaps in thermal comfort models, and key strategies in the development of useable, comfortable outdoor spaces for older adults. Integrative reviews allow for new frameworks or perspectives on a subject to be introduced. Uncovering the synergy of these three knowledge bases can contribute to guiding microclimatic research, design practitioners, and care providers as they seek safe, comfortable and inviting outdoor spaces for aging adults.
Collapse
Affiliation(s)
- Daniel J Vecellio
- Climate Science Lab, Department of Geography, Texas A&M University, College Station, TX, USA.
| | - Eric K Bardenhagen
- Department of Plant and Soil Sciences, University of Delaware, Newark, DE, USA; Center for Health Systems & Design, Texas A&M University, College Station, TX, USA
| | - Ben Lerman
- Department of Biological Sciences, Hunter College of the City University of New York, New York, NY, USA
| | - Robert D Brown
- Department of Landscape Architecture and Urban Planning, Texas A&M University, College Station, TX, USA; Center for Health Systems & Design, Texas A&M University, College Station, TX, USA
| |
Collapse
|
13
|
Morris NB, Chaseling GK, English T, Gruss F, Maideen MFB, Capon A, Jay O. Electric fan use for cooling during hot weather: a biophysical modelling study. Lancet Planet Health 2021; 5:e368-e377. [PMID: 34119011 DOI: 10.1016/s2542-5196(21)00136-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 04/28/2021] [Accepted: 04/29/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND In hot weather, electric fans can potentially provide effective cooling for people, with lower greenhouse gas emissions and cost than air conditioning. However, international public health organisations regularly discourage fan use in temperatures higher than 35°C, despite little evidence. We aimed to determine humidity-dependent temperature thresholds at which electric fans would become detrimental in different age groups. METHODS We used biophysical modelling to determine the upper humidity-dependent temperature thresholds at which fan use would become detrimental (ie, worsen heat stress) for healthy young adults (aged 18-40 years), healthy older adults (aged ≥65 years), and older adults taking anticholinergic medication. We also obtained hourly environmental data for the period Jan 1, 2007, to Dec 31, 2019, for 108 populous cities to determine the number of days fan use would be effective for cooling, standardised to a 31-day hot weather month. We established simplified temperature thresholds for future fan use recommendations on the basis of temperatures below which fan use would never have been detrimental between Jan 1, 2007, and Dec 31, 2019, across all prevailing levels of ambient humidity. FINDINGS According to our model, fan use would have been beneficial on 30·0 (96·6%) of 31 hot weather days for healthy young adults and 29·4 (94·9%) of 31 hot weather days for both older adults and older adults taking anticholinergic medication between Jan 1, 2007, and Dec 31, 2019. Adherence to the current WHO recommendation of fan use below temperatures of 35°C only, fan use would have been recommended on 27·2 days (87·7%) of 31 hot weather days. According to our simplified thresholds for fan use (at temperatures <39·0°C for healthy young adults, <38·0°C for healthy older adults, and <37·0°C for older adults taking anticholinergic medication), fan use would have been recommended on 29·6 (95·5%) of 31 hot weather days in healthy young adults, 29·4 (94·8%) days in healthy older adults, and 28·8 (93·0%) days in older adults taking anticholinergic medication between Jan 1, 2007, and Dec 31, 2019. INTERPRETATION Electric fan use, particularly for healthy young adults, would not have worsened heat stress on the majority of study days between 2007 and 2019. Our newly proposed thresholds for fan use provide simple guidelines that improve future heatwave fan use recommendations. FUNDING None.
Collapse
Affiliation(s)
- Nathan B Morris
- Thermal Ergonomics Laboratoryxs, The University of Sydney, Sydney, NSW, Australia; Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Georgia K Chaseling
- Thermal Ergonomics Laboratoryxs, The University of Sydney, Sydney, NSW, Australia; Department of Pharmacology and Physiology, University of Montreal, Montreal, QC, Canada
| | - Timothy English
- Thermal Ergonomics Laboratoryxs, The University of Sydney, Sydney, NSW, Australia; Faculty of Medicine and Health, and Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia
| | - Fabian Gruss
- Thermal Ergonomics Laboratoryxs, The University of Sydney, Sydney, NSW, Australia
| | | | - Anthony Capon
- Sydney School of Public Health, The University of Sydney, Sydney, NSW, Australia; Monash Sustainable Development Institute, Monash University, Melbourne, VIC, Australia
| | - Ollie Jay
- Thermal Ergonomics Laboratoryxs, The University of Sydney, Sydney, NSW, Australia; Sydney School of Public Health, The University of Sydney, Sydney, NSW, Australia; Faculty of Medicine and Health, and Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia.
| |
Collapse
|
14
|
Cramer MN, Huang M, Fischer M, Moralez G, Crandall CG. Thermoregulatory Responses with Size-matched Simulated Torso or Limb Skin Grafts. Med Sci Sports Exerc 2021; 53:2190-2195. [PMID: 33935232 PMCID: PMC8440327 DOI: 10.1249/mss.0000000000002694] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Skin grafting following a burn injury attenuates/abolishes sweat production within grafted areas. It is presently unknown whether the thermoregulatory consequences of skin grafting depend on anatomical location. PURPOSE To test the hypothesis that a simulated burn injury on the torso will be no more or less detrimental to core temperature control than on the limbs during uncompensable exercise-heat stress. METHODS Nine non-burned individuals (7 males, 2 females) completed the protocol. On separate occasions, burn injuries of identical surface area (0.45 ± 0.08 m2 or 24.4% ± 4.4% of total body surface area) were simulated on the torso or the arms/legs using an absorbent, vapor-impermeable material that impedes sweat evaporation in those regions. Participants performed 60 min of treadmill walking at 5.3 km·h-1 and a 4.1% ± 0.8% grade, targeting 6 W·kg-1 of metabolic heat production in 40.1°C ± 0.2°C and 19.6% ± 0.6% relative humidity conditions. Rectal temperature, heart rate, and perceptual responses were measured. RESULTS Rectal temperature increased to a similar extent with simulated injuries on the torso and limbs (condition-by-time interaction: P = 0.86), with a final rectal temperature 0.9 ± 0.3°C above baseline in both conditions. No differences in heart rate, perceived exertion, or thermal sensation were observed between conditions (condition-by-time interactions: P ≥ 0.50). CONCLUSION During uncompensable exercise-heat stress, sized-matched simulated burn injuries on the torso or limbs evoke comparable core temperature, heart rate, and perceptual responses, suggesting that the risk of exertional heat illness in such environmental conditions is independent of injury location.
Collapse
Affiliation(s)
- Matthew N Cramer
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX, USA Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, USA Department of Nutrition, Exercise and Sports, University of Copenhagen and Department of Anaesthesiology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | | | | | | | | |
Collapse
|
15
|
Fischer M, Cramer MN, Huang MU, Belval LN, Watso JC, Cimino FA, Crandall CG. Burn Injury Does Not Exacerbate Heat Strain during Exercise while Wearing Body Armor. Med Sci Sports Exerc 2021; 52:2235-2241. [PMID: 32936596 DOI: 10.1249/mss.0000000000002375] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION Although evaporative heat loss capacity is reduced in burn-injured individuals with extensive skin grafts, the thermoregulatory strain due to a prior burn injury during exercise-heat stress may be negligible if the burn is located underneath protective clothing with low vapor permeability. PURPOSE This study aimed to test the hypothesis that heat strain during exercise in a hot-dry environment while wearing protective clothing would be similar with and without a simulated torso burn injury. METHODS Ten healthy individuals (8 men/2 women) underwent three trials wearing: uniform (combat uniform, tactical vest, and replica torso armor plates), uniform with a 20% total body surface area simulated torso burn (uniform + burn), or shorts (and sports bra) only (control). Exercise consisted of treadmill walking (5.3 km·h; 3.7% ± 0.9% grade) for 60 min at a target heat production of 6.0 W·kg in 40.0°C ± 0.1°C and 20.0% ± 0.6% relative humidity conditions. Measurements included rectal temperature, heart rate, ratings of perceived exertion (RPE), and thermal sensation. RESULTS No differences in rectal temperature (P ≥ 0.85), heart rate (P ≥ 0.99), thermal sensation (P ≥ 0.73), or RPE (P ≥ 0.13) occurred between uniform + burn and uniform trials. In the control trial, however, core temperature, heart rate, thermal sensation, and RPE were lower compared with the uniform and uniform + burn trials (P ≤ 0.04 for all). CONCLUSIONS A 20% total body surface area simulated torso burn injury does not further exacerbate heat strain when wearing a combat uniform. These findings suggest that the physiological strain associated with torso burn injuries is not different from noninjured individuals when wearing protective clothing during an acute exercise-heat stress.
Collapse
Affiliation(s)
| | | | | | - Luke N Belval
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX
| | - Joseph C Watso
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX
| | - Frank A Cimino
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX
| | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX
| |
Collapse
|
16
|
Hospers L, Smallcombe JW, Morris NB, Capon A, Jay O. Electric fans: A potential stay-at-home cooling strategy during the COVID-19 pandemic this summer? THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 747:141180. [PMID: 32768770 PMCID: PMC7381401 DOI: 10.1016/j.scitotenv.2020.141180] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/10/2020] [Accepted: 07/21/2020] [Indexed: 05/29/2023]
Abstract
Current public health guidance designed to protect individuals against extreme heat and the ongoing COVID-19 pandemic is seemingly discordant, yet during the northern hemisphere summer, we are faced with the imminent threat of their simultaneous existence. Here we examine the environmental limits of electric fan-use in the context of the United States summer as a potential stay-at-home cooling strategy that aligns with existing efforts to mitigate the spread of SARS-COV-2.
Collapse
Affiliation(s)
- Lily Hospers
- Sydney School of Health Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, Australia
| | - James W Smallcombe
- Sydney School of Health Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, Australia
| | - Nathan B Morris
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Anthony Capon
- Monash Sustainable Development Institute, Monash University, Melbourne, Australia
| | - Ollie Jay
- Sydney School of Health Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, Australia; Charles Perkins Centre, The University of Sydney, Sydney, Australia.
| |
Collapse
|
17
|
Gravel H, Chaseling GK, Barry H, Debray A, Gagnon D. Cardiovascular control during heat stress in older adults: time for an update. Am J Physiol Heart Circ Physiol 2020; 320:H411-H416. [PMID: 33275528 DOI: 10.1152/ajpheart.00536.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is generally accepted that older adults display an impaired cardiovascular response to heat stress, and it has been suggested that this impaired response contributes to their increased risk of mortality during extreme heat events. Seminal studies have shown that cutaneous vasodilation, the redistribution of blood flow from visceral organs, and the increase in cardiac output are blunted in older adults during passive heating. The blunted rise of cardiac output was initially attributed to an inability to maintain stroke volume, suggesting that cardiac systolic and/or diastolic function does not adequately respond to the constraints of heat stress in older adults. Recent studies evaluated potential mechanisms underlying these seminal findings and their results challenge some of these initial observations. Notably, stroke volume is maintained during heat exposure in older adults and studies have provided evidence for preserved cardiac systolic and diastolic functions in this population. Nonetheless, a blunted increase in cardiac output during heat exposure remains a consistent observation in older adults, although it is now attributed to a blunted increase in heart rate. Recent studies have also evaluated the possibility that the attenuated capacity of aged skin to vasodilate contributes to a blunted increase in cardiac output during heat stress. The objective of this Mini-Review is to highlight these recent advances and challenge the long-standing view that the control of stroke volume during heat exposure is compromised in older adults. By doing so, our intent is to stimulate future studies to evaluate several unanswered questions in this area of research.
Collapse
Affiliation(s)
- Hugo Gravel
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montreal, Quebec, Canada.,Research Centre, Montreal Heart Institute, Montreal, Quebec, Canada.,Department of Pharmacology and Physiology, Université de Montréal, Montreal, Quebec, Canada
| | - Georgia K Chaseling
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montreal, Quebec, Canada.,Research Centre, Montreal Heart Institute, Montreal, Quebec, Canada.,Department of Pharmacology and Physiology, Université de Montréal, Montreal, Quebec, Canada
| | - Hadiatou Barry
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montreal, Quebec, Canada.,Research Centre, Montreal Heart Institute, Montreal, Quebec, Canada.,Department of Pharmacology and Physiology, Université de Montréal, Montreal, Quebec, Canada
| | - Amélie Debray
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montreal, Quebec, Canada.,Research Centre, Montreal Heart Institute, Montreal, Quebec, Canada.,Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
| | - Daniel Gagnon
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montreal, Quebec, Canada.,Research Centre, Montreal Heart Institute, Montreal, Quebec, Canada.,Department of Pharmacology and Physiology, Université de Montréal, Montreal, Quebec, Canada.,School of Kinesiology and Exercise Science, Université de Montréal, Montreal, Quebec, Canada
| |
Collapse
|
18
|
Daanen H, Bose-O'Reilly S, Brearley M, Flouris DA, Gerrett NM, Huynen M, Jones HM, Lee JKW, Morris N, Norton I, Nybo L, Oppermann E, Shumake-Guillemot J, Van den Hazel P. COVID-19 and thermoregulation-related problems: Practical recommendations. Temperature (Austin) 2020; 8:1-11. [PMID: 33553500 PMCID: PMC7849778 DOI: 10.1080/23328940.2020.1790971] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The COVID-19 pandemic started in the cold months of the year 2020 in the Northern hemisphere. Concerns were raised that the hot season may lead to additional problems as some typical interventions to prevent heat-related illness could potentially conflict with precautions to reduce coronavirus transmission. Therefore, an international research team organized by the Global Health Heat Information Network generated an inventory of the specific concerns about this nexus and began to address the issues. Three key thermal and covid-19 related topics were highlighted: 1) For the general public, going to public cool areas in the hot season interferes with the recommendation to stay at home to reduce the spread of the virus. Conflicting advice makes it necessary to revise national heat plans and alert policymakers of this forecasted issue. 2) For medical personnel working in hot conditions, heat strain is exacerbated due to a reduction in heat loss from wearing personal protective equipment to prevent contamination. To avoid heat-related injuries, medical personnel are recommended to precool and to minimize the increase in body core temperature using adopted work/rest schedules, specific clothing systems, and by drinking cold fluids. 3) Fever, one of the main symptoms of COVID-19, may be difficult to distinguish from heat-induced hyperthermia and a resting period may be necessary prior to measurement to avoid misinterpretation. In summary, heat in combination with the COVID-19 pandemic leads to additional problems; the impact of which can be reduced by revising heat plans and implementing special measures attentive to these compound risks.
Collapse
Affiliation(s)
- Hein Daanen
- Department of Human Movement Sciences. Faculty of Behavioral and Movement Sciences. Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Stephan Bose-O'Reilly
- Institute and Clinic for Occupational, Social and Environmental Medicine, University Hospital, LMU Munich, Germany.,Institute for Public Health, Medical Decision Making and HTA, UMIT - Private University for Health Sciences, Medical Informatics and Technology, Hall i.T., Austria.,Hospital St. Hedwig of the Order of St. John, Institute and Clinic for Occupational, Social and Environmental Medicine, University Children's Hospital Regensburg (KUNO), University of Regensburg, Regensburg, Munich, Germany
| | - Matt Brearley
- National Critical Care and Trauma Response Centre, Australia
| | - D Andreas Flouris
- FAME Laboratory, Department of Exercise Science, University of Thessaly, Greece
| | - Nicola M Gerrett
- Department of Human Movement Sciences. Faculty of Behavioral and Movement Sciences. Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Maud Huynen
- Maastricht University Institute (MSI), Maastricht University, Maastricht, The Netherlands
| | - Hunter M Jones
- University Corporation for Atmospheric Research in Service to the U.S. National Oceanic & Atmospheric Administration, Silver Spring, MD, USA
| | - Jason Kai Wei Lee
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Global Asia Institute, National University of Singapore, Singapore.,N.1 Institute for Health, National University of Singapore, Singapore
| | | | - Ian Norton
- Respond Global, Australia.,Previously World Health Organization, Switzerland
| | - Lars Nybo
- University of Copenhagen, Copenhagen, Denmark
| | - Elspeth Oppermann
- Department Für Geographie, Ludwig-Maximilians-Universität München, Germany
| | | | | |
Collapse
|
19
|
Millyard A, Layden JD, Pyne DB, Edwards AM, Bloxham SR. Impairments to Thermoregulation in the Elderly During Heat Exposure Events. Gerontol Geriatr Med 2020; 6:2333721420932432. [PMID: 32596421 PMCID: PMC7297481 DOI: 10.1177/2333721420932432] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 05/06/2020] [Accepted: 05/14/2020] [Indexed: 12/11/2022] Open
Abstract
Heat waves represent a public health risk to elderly people, and typically result in an increased rate of hospital admissions and deaths. Studies of thermoregulation in this cohort have generally focused on single elements such as sweating capacity. Sweating capacity and skin blood flow reduce with age, reducing ability to dissipate heat. Perception of effort during heat exposure is emerging as an area that needs further investigation as the elderly appear to lack the ability to adequately perceive increased physiological strain during heat exposure. The role of the gut and endotoxemia in heat stress has received attention in young adults, while the elderly population has been neglected. This shortcoming offers another potential avenue for identifying effective integrated health interventions to reduce heat illnesses. Increasing numbers of elderly individuals in populations worldwide are likely to increase the incidence of heat wave-induced deaths if adequate interventions are not developed, evaluated, and implemented. In this narrative-style review we identify and discuss health-related interventions for reducing the impact of heat illnesses in the elderly.
Collapse
Affiliation(s)
| | | | - David B Pyne
- University of Canberra, Australian Capital Territory, Australia
| | | | | |
Collapse
|
20
|
Cramer MN, Huang M, Moralez G, Crandall CG. Keeping older individuals cool in hot and moderately humid conditions: wetted clothing with and without an electric fan. J Appl Physiol (1985) 2020; 128:604-611. [PMID: 32027545 DOI: 10.1152/japplphysiol.00786.2019] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The present study evaluated whether wearing a water-soaked t-shirt, with or without electric fan use, mitigates thermal and cardiovascular strain in older individuals exposed to hot and moderately humid conditions. Nine healthy older individuals (68 ± 4 yr; five women) completed three 120-min heat exposures (42.4 ± 0.2°C, 34.2 ± 0.9% relative humidity) on separate days while wearing a dry t-shirt (CON), a t-shirt soaked with 500 ml of tap water (WET), or a t-shirt soaked with 500 ml of tap water while facing an electric fan (2.4 ± 0.4 m/s; WET+FAN). Measurements included core and skin temperatures, evaporative mass losses, heart rate, and blood pressure. In the WET condition, elevations in core temperature were attenuated compared with DRY from 30 to 120 min and compared with WET+FAN from 30 to 90 min (P < 0.05). Evaporative mass losses (inclusive of sweat and water losses from the shirt) were greatest in WET+FAN, followed by WET, and then DRY (P < 0.01). Sweat losses were lowest in WET, followed by DRY, and then WET+FAN (P < 0.01). Heart rate was lower only at 60 min in WET versus DRY (P = 0.01). No differences in mean arterial pressure were observed (P = 0.51). In conclusion, wearing a water-soaked t-shirt without, but not with, electric fan use is an effective heat management strategy to mitigate thermal strain and lower sweat losses in older individuals exposed to hot and moderately humid conditions.NEW & NOTEWORTHY In older individuals exposed to hot and moderately humid environments, electric fan use coupled with a water-soaked t-shirt exacerbates sweat losses without mitigating heat strain compared with a dry t-shirt. However, wearing a water-soaked t-shirt without fan use reduces sweat losses and attenuates heat strain compared with a dry t-shirt and a fan/water-soaked t-shirt combination. These findings suggest wearing a water-soaked t-shirt is an effective heat-management strategy for older individuals during heat waves when air conditioning is inaccessible.
Collapse
Affiliation(s)
- Matthew N Cramer
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
| | - Mu Huang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas.,Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Gilbert Moralez
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas.,Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, Texas
| |
Collapse
|
21
|
Chaseling GK, Crandall CG, Gagnon D. Skin blood flow measurements during heat stress: technical and analytical considerations. Am J Physiol Regul Integr Comp Physiol 2019; 318:R57-R69. [PMID: 31596109 DOI: 10.1152/ajpregu.00177.2019] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
During heat stress, the skin vasculature can greatly increase conductance secondary to vasodilation. The subsequent increase in skin blood flow allows for convective heat transfer from the core to the skin and between the skin surface and the surrounding environment. Measurement of skin blood flow, therefore, provides valuable information regarding heat exchange between the body and the environment. In addition, assessment of skin blood flow can be used to study vascular control mechanisms. Most often, skin blood flow is measured by venous occlusion plethysmography, Doppler ultrasound, laser-Doppler flowmetry, and, more recently, optical coherence tomography. However, important delimitations to each of these methods, which may be dependent on the research question, must be considered when responses from these approaches are interpreted. In this brief review, we discuss these methods of skin blood flow measurement and highlight potential sources of error and limitations. We also provide recommendations to guide the interpretation of skin blood flow data.
Collapse
Affiliation(s)
- Georgia K Chaseling
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, Québec, Canada.,Département de Pharmacologie et Physiologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
| | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, and University of Texas Southwestern Medical Center, Dallas, Texas
| | - Daniel Gagnon
- Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, Québec, Canada.,Département de Pharmacologie et Physiologie, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
| |
Collapse
|
22
|
Meade RD, Notley SR, Kenny GP. Aging and human heat dissipation during exercise-heat stress: an update and future directions. CURRENT OPINION IN PHYSIOLOGY 2019. [DOI: 10.1016/j.cophys.2019.07.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
|
23
|
Hosokawa Y, Casa DJ, Trtanj JM, Belval LN, Deuster PA, Giltz SM, Grundstein AJ, Hawkins MD, Huggins RA, Jacklitsch B, Jardine JF, Jones H, Kazman JB, Reynolds ME, Stearns RL, Vanos JK, Williams AL, Williams WJ. Activity modification in heat: critical assessment of guidelines across athletic, occupational, and military settings in the USA. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2019; 63:405-427. [PMID: 30710251 PMCID: PMC10041407 DOI: 10.1007/s00484-019-01673-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 01/13/2019] [Accepted: 01/15/2019] [Indexed: 05/04/2023]
Abstract
Exertional heat illness (EHI) risk is a serious concern among athletes, laborers, and warfighters. US Governing organizations have established various activity modification guidelines (AMGs) and other risk mitigation plans to help ensure the health and safety of their workers. The extent of metabolic heat production and heat gain that ensue from their work are the core reasons for EHI in the aforementioned population. Therefore, the major focus of AMGs in all settings is to modulate the work intensity and duration with additional modification in adjustable extrinsic risk factors (e.g., clothing, equipment) and intrinsic risk factors (e.g., heat acclimatization, fitness, hydration status). Future studies should continue to integrate more physiological (e.g., valid body fluid balance, internal body temperature) and biometeorological factors (e.g., cumulative heat stress) to the existing heat risk assessment models to reduce the assumptions and limitations in them. Future interagency collaboration to advance heat mitigation plans among physically active population is desired to maximize the existing resources and data to facilitate advancement in AMGs for environmental heat.
Collapse
Affiliation(s)
- Yuri Hosokawa
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA.
- College of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan.
| | - Douglas J Casa
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA
| | - Juli M Trtanj
- National Oceanic and Atmospheric Administration, Washington DC, USA
| | - Luke N Belval
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA
| | - Patricia A Deuster
- Consortium for Health and Military Performance, Department of Military and Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Sarah M Giltz
- National Oceanic and Atmospheric Administration, Washington DC, USA
- Louisiana Sea Grant, Louisiana State University, Baton Rouge, LA, USA
| | | | | | - Robert A Huggins
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA
| | - Brenda Jacklitsch
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
| | - John F Jardine
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA
| | - Hunter Jones
- National Oceanic and Atmospheric Administration, Washington DC, USA
- University Corporation for Atmospheric Research, Boulder, CO, USA
| | - Josh B Kazman
- Consortium for Health and Military Performance, Department of Military and Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Mark E Reynolds
- U.S. Army Public Health Center, Aberdeen Proving Ground, Aberdeen, MD, USA
| | - Rebecca L Stearns
- Korey Stringer Institute, University of Connecticut, Storrs, CT, USA
| | - Jennifer K Vanos
- Scripps Institution of Oceanography Department, University of California San Diego, La Jolla, CA, USA
| | - Alan L Williams
- Walter Reed National Military Medical Center, Bethesda, MD, USA
| | - W Jon Williams
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
| |
Collapse
|
24
|
Gagnon D, Romero SA, Cramer MN, Kouda K, Poh PYS, Ngo H, Jay O, Crandall CG. Folic acid supplementation does not attenuate thermoregulatory or cardiovascular strain of older adults exposed to extreme heat and humidity. Exp Physiol 2018; 103:1123-1131. [PMID: 29873123 DOI: 10.1113/ep087049] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 05/29/2018] [Indexed: 01/28/2023]
Abstract
NEW FINDINGS What is the central question of this study? Does folic acid supplementation alleviate thermoregulatory and cardiovascular strain of older adults during exposure to extreme heat and humidity? What is the main finding and its importance? Folic acid supplementation for 6 weeks did not affect whole-limb blood flow/vasodilatation, core and skin temperatures, heart rate, blood pressure and cardiac output. Thus, 6 weeks of folic acid supplementation does not alleviate thermoregulatory or cardiovascular strain of healthy older adults exposed to extreme heat and humidity. ABSTRACT Folic acid supplementation reverses age-related reductions in cutaneous vasodilatation during passive heating. However, it is unknown if folic acid supplementation alleviates thermoregulatory and cardiovascular strain experienced by older adults during heat exposure. We evaluated the effect of folic acid supplementation on thermoregulatory and cardiovascular responses of nine healthy older adults (61-72 years, 3 males/6 females) exposed to extreme heat and humidity. Participants rested at 42°C while relative humidity was increased from 30% to 70% in 2% increments every 5 min. The protocol was performed before (CON) and after (FOLIC) 6 weeks of folic acid supplementation (5 mg day-1 ). Local cutaneous vascular conductance (CVC, laser-Doppler flowmetry), forearm vascular conductance (FVC, Doppler ultrasound), mean skin and oesophageal temperatures, heart rate, blood pressure and cardiac output were measured. Folic acid supplementation increased fasting serum folate concentrations (P < 0.01). Absolute CVC was greater throughout the protocol following supplementation (CON: 1.29 ± 0.16 units mmHg-1 vs. FOLIC: 1.65 ± 0.24 units mmHg-1 , P < 0.01). However, normalized CVC (CON: 54 ± 8% vs. FOLIC: 59 ± 7%, P = 0.22), FVC (CON: 3.47 ± 0.76 ml mmHg-1 vs. FOLIC: 3.40 ± 0.56 ml mmHg-1 , P = 0.93), mean skin (P = 0.81) and oesophageal (CON: 36.87 ± 0.28°C vs. folic: 36.90 ± 0.25°C, P = 0.98) temperatures, heart rate (CON: 83 ± 10 beats min-1 vs. FOLIC: 84 ± 8 beats min-1 , P = 0.64), blood pressure (P = 0.71) and cardiac output (P = 0.20) were unaffected by folic acid supplementation. These results demonstrate that 6 weeks of folic acid supplementation does not alleviate thermoregulatory or cardiovascular strain of healthy older adults exposed to extreme heat and humidity.
Collapse
Affiliation(s)
- Daniel Gagnon
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX, USA.,Cardiovascular Prevention and Rehabilitation Centre, Montreal Heart Institute, Montréal, QC, Canada.,Département de Pharmacologie et Physiologie, Faculté de Médecine, Université de Montréal, Montréal, QC, Canada
| | - Steven A Romero
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Matthew N Cramer
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Ken Kouda
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX, USA.,Wakayama Medical University, Wakayama, Japan
| | - Paula Y S Poh
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Hai Ngo
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Ollie Jay
- Faculty of Health Sciences, University of Sydney, Lidcombe, Australia
| | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center, Dallas, TX, USA
| |
Collapse
|
25
|
Kenny GP, Flouris AD, Yagouti A, Notley SR. Towards establishing evidence-based guidelines on maximum indoor temperatures during hot weather in temperate continental climates. Temperature (Austin) 2018; 6:11-36. [PMID: 30906809 PMCID: PMC6422495 DOI: 10.1080/23328940.2018.1456257] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 03/15/2018] [Indexed: 11/09/2022] Open
Abstract
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.
Collapse
Affiliation(s)
- Glen P. Kenny
- Human and Environmental Physiology Research Unit, Faculty of Health Sciences, University of Ottawa, Ottawa, Ontario, Canada
| | - Andreas D. Flouris
- FAME Laboratory, Department of Exercise Science, University of Thessaly, Trikala, Greece
| | | | - Sean R. Notley
- Human and Environmental Physiology Research Unit, Faculty of Health Sciences, University of Ottawa, Ottawa, Ontario, Canada
| |
Collapse
|
26
|
Leicht AS, Flouris AD, Kaltsatou A, Seely AJ, Herry CL, Wright Beatty HE, Kenny GP. Age alters cardiac autonomic modulations during and following exercise-induced heat stress in females. Temperature (Austin) 2018; 5:184-196. [PMID: 30377635 DOI: 10.1080/23328940.2018.1432918] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 01/26/2018] [Accepted: 02/07/2018] [Indexed: 12/19/2022] Open
Abstract
The aim of this study was to examine the effect of natural ageing on heart rate variability during and following exercise-induced heat stress in females. Eleven young (∼24 years) and 13 older (∼51 years), habitually active females completed an experimental session consisting of baseline rest, moderate intensity intermittent exercise (four 15-min bouts separated by 15-min recovery) and 1-hour of final recovery in a hot and dry (35°C, 20% relative humidity) environment. Respiratory and heart rate recordings were continuously logged with 10-min periods analysed at the end of: baseline rest; each of the exercise and recovery bouts; and during the 1-hour final recovery period. Comparisons over time during exercise and recovery, and between groups were conducted via two-way repeated-measures ANCOVAs with rest values as the covariate. During baseline rest, older females exhibited lower heart rate variability compared to young females with similar levels of respiration and most (∼71-79%) heart rate variability measures during repeated exercise and recovery. However, older females exhibited heart rate variability metrics suggestive of greater parasympathetic modulation (greater long axis of Poincare plot, cardiac vagal index; lower low-high frequency ratio) during repeated exercise with lower indices during the latter stage of prolonged recovery (less very low frequency component, Largest Lyapunov Exponent; greater cardiac sympathetic index). The current study documented several unique, age-dependent differences in heart rate variability, independent of respiration, during and following exercise-induced heat stress for females that may assist in the detection of normal heat-induced adaptations as well as individuals vulnerable to heat stress.
Collapse
Affiliation(s)
- Anthony S Leicht
- Sport and Exercise Science, James Cook University, Townsville, Australia
| | - Andreas D Flouris
- FAME Laboratory, Department of Exercise Science, University of Thessaly, Trikala, Greece
| | - Antonia Kaltsatou
- FAME Laboratory, Department of Exercise Science, University of Thessaly, Trikala, Greece
| | - Andrew J Seely
- Divisions of Thoracic Surgery and Critical Care Medicine, Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Christophe L Herry
- Dynamical Analysis Lab, Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ontario, Canada
| | | | - Glen P Kenny
- Human and Environmental Physiology Research Unit, University of Ottawa, Ontario, Canada
| |
Collapse
|