Impact of Heat and Mitigation Strategies on Healthcare Professionals: A Scoping Review

ABSTRACT

Background

Rising global temperatures and increased use of personal protective equipment has led to increased risk of heat stress amongst healthcare professionals. This review synthesizes recent research on the impact of heat and heat mitigation strategies on healthcare professionals across disciplines and settings.

Method

Databases were systematically searched using keywords and data from included studies were extracted for content analysis.

Results

Among 15 eligible studies, 13 investigated the impact of heat stress on healthcare professionals. Six investigated mitigation strategies. Most studies utilized survey methodology and were related to the use of personal protective equipment during the recent pandemic. Large proportions of healthcare professionals reported high levels of thermal discomfort and preferred a cooler temperature in the workplace. The most commonly reported heat strain symptoms included sweating, fatigue, thirst, and poor or reduced concentration. Investigation of mitigation strategies has thus far focused on individual strategies with little insights gained into organizational support or heat policy.

Conclusions

Supporting healthcare professionals to manage the impact of heat stress has received little attention in the literature. Mitigation strategies have thus far focused predominantly upon individual strategies. Future studies should adopt a more comprehensive approach to investigating healthcare professional's experiences, investigating all levels of controls.

1. Background

The World Health Organization identifies heat as an important environmental and occupational health hazard (WHO ^2024a, para 1). Heat stress results when the body is unable to thermoregulate in response to heat production (Cheung, McLellan, and Tenaglia ²⁰⁰⁰). Heat stress has a substantial impact on mortality and morbidity of general populations (Baker et al. 2022; Rocque et al. ²⁰²¹). Most of the research on the impact of heat stress upon particular occupational groups has focused on professionals who work outside and are exposed to ambient heat and radiant heat from the sun (Habibi et al. 2021; Ioannou et al. ²⁰²²; Moda et al. ²⁰¹⁹).

Healthcare professionals encompass a broad range of professions including allied health professionals, nurses, paramedics, and doctors. The roles and contexts in which they work are equally broad, ranging from hospitals to community‐based settings. Some of these roles and contexts require healthcare professionals to wear personal protective equipment (PPE). For example, during the recent COVID‐19 pandemic testing and triage was performed by health professionals in full PPE. Sometimes this testing was conducted outside or in tents in all seasons and temperatures. Recommendations were published during the pandemic for maintaining healthy thermoregulation during hot summer months whilst wearing PPE (Daanen et al. 2020). These recommendations included precooling, adoption of shorter work/rest schedules, and drinking cool fluids (Daanen et al. 2020). The significant and increasing impact of heat on healthcare professionals demonstrates the importance of understanding the impact of heat on this population and ways to manage heat stress.

To date, no reviews have investigated the impact of heat stress upon healthcare professionals and the mitigation strategies they employed. For the purpose of this paper, the term heat mitigation refers to actions to reduce the severity or seriousness of the impacts of heat on an individual (Morris et al. 2020). The extent of heat stress amongst healthcare professionals, what mitigation strategies are available to them and which strategies they find practical to use during their work is currently unclear. For these reasons, a scoping review was conducted to systematically map the research done in the area and identify existing gaps in knowledge.

The aim of this review was to examine the current evidence base investigating the impact of heat stress upon healthcare professionals and mitigation strategies employed to address heat stress. The following research questions were used to guide the review. How does heat stress impact healthcare professionals? What professional populations and in which health contexts has the impact of heat stress been investigated? What mitigation strategies do healthcare professionals employ to manage heat stress? What facilitators and barriers to the implementation of mitigation strategies have been identified?

2. Method

The protocol for this scoping review was registered with the Open Science Framework and can be accessed at the following URL: https://osf.io/h5be2/. The protocol was changed in November 2023, after initial searches found too few papers to focus solely upon Australian healthcare professionals and the review was expanded to encompass studies from any country. This review followed guidance from Chapter 11 of the Joanna Briggs Institute Manual for Evidence Synthesis (Peters et al. 2020) and the PRISMA‐ScR statement (Tricco et al. 2018).

2.1. Databases Searches and Search Strategy

A systematic search, designed to be deliberately broad to ensure all potentially relevant records were included in the scoping review, was carried out in June 2023 in three stages. An initial search was conducted in EBSCOhost: CINAHL. Titles, abstracts, and index terms, from a selection of retrieved records were scrutinized to see if additional keywords could be identified. The following bibliographic databases were searched from 2009 to June 2023: Academic Search Complete via Ebscohost, CINAHL via Ebscohost, Health & Medicine Databases via ProQuest, ProQuest Dissertations & Theses Global, Emcare via Ovid and Informit Health Collection (Appendix A). Key search terms and subject headings employed in searches related to; population: health workforce including doctors, nurses, allied health including paramedics; intervention: mitigation strategies such as ice vests or cold drinks; and condition: thermal or heat stress or strain. The final search strategy is listed in Appendix A. Citation searching of all reports included in the scoping review was completed to identify any additional sources.

2.2. Selection of Studies

Search results were exported into EndNoteX9 and duplicates were removed. The EndNote file was uploaded to Covidence. The inclusion and exclusion criteria were used to develop screening questions which were tested during research meetings with all reviewers by screening a study and discussing the results. Title and abstract screening were conducted by one reviewer against inclusion and exclusion criteria (Table 1) and ineligible records were removed from further consideration. All potentially eligible reports were retained for full‐text review. Two reviewers independently screened full texts of potentially relevant reports, and reasons for ineligibility were noted. Disagreements between reviewers were resolved by discussion as a team and ineligible reports were removed from further consideration.

TABLE 1.

Study eligibility criteria.

Inclusion criteria	Exclusion criteria
Studies which included healthcare workers (nurses, doctors, allied health, paramedics)	Studies about general population or non‐healthcare workforce
Research focuses on effects and mitigation of heat stress. Published between 2009 to present English language publication Peer‐reviewed published research including quantitative, qualitative and mixed methods studies	Study did not focus on effects and mitigation of heat stress Published in languages other than English Review articles, conference proceedings and posters, non‐peer reviewed research (including gray literature and opinion papers)

2.3. Data Extraction and Synthesis

A charting table was developed and piloted using two included papers to ensure that all relevant findings were identified. This included data on study characteristics (e.g., country, setting), population characteristics (e.g., healthcare profession, participant characteristics), description of the study, and findings. Data from all included papers were independently extracted by two reviewers. All reviewers extracted data, and then one reviewer combined the data in consultation with other reviewers to clarify data tabulation were needed. A narrative approach was taken to synthesize key findings from the included studies. Findings were grouped into studies that investigated the impact of heat stress upon the health workforce and studies that investigated mitigation strategies that the health workforce employed to manage heat stress.

3. Results

3.1. Identification and Selection of Studies

The PRISMA flow diagram in Figure 1 summarizes the results and stages employed to identify and select studies for inclusion in the review. Eight thousand fifty‐nine records were identified from four databases and 2509 duplicates were removed prior to screening. Five thousand three hundred and forty‐six records were excluded during title and abstract screening and full text of 204 records were found. Two hundred three records were screened by two reviewers resulting in exclusion of 189 records. One record was identified during citation searching of included studies. Thus, 15 records of 15 studies were included in this review.

FIGURE 1.

PRISMA 2020 flow diagram for new systematic reviews which included searches of databases, registers and other sources.

3.2. Characteristics of Included Studies

Characteristics of included studies (n = 15) are collated in Table 2 (Bongers et al. 2022; Davey et al. ²⁰²¹; De Korte et al. ²⁰²²; Derks et al. ²⁰¹⁸; Grélot et al. ²⁰¹⁶; Hakim et al. ²⁰¹⁸; Hunt et al.’s ²⁰²³; Jegodka et al. ²⁰²¹; Karahan et al. ²⁰²²; Langø et al. ²⁰⁰⁹; Lee et al. ²⁰²⁰; Messeri et al. ²⁰²¹; Palejwala et al. ²⁰²³; Tabah et al. ²⁰²⁰; Unoki et al. ²⁰²⁰). Most studies were completed in the last decade, with only one study (Langø et al. 2009) completed prior to 2013. Most of the studies were undertaken in Europe (n = 8), Australia (n = 2), and one worldwide survey (Tabah et al. 2020). In addition, one study was completed in Guinea (Africa), but was a study by French academics on French healthcare professionals (Grélot et al. 2016). Nine out of the 15 included studies were descriptive survey‐based research. Only one study used a participatory approach as part of their methodology (Langø et al. 2009). Studies were predominantly located in hospitals (n = 14). One study took place in an Ebola clinic (Grélot et al. 2016). Tabah et al. (2020) reported that 7% of respondents from their worldwide survey reported working in remote or regional areas, and no other studies reported regional locations. Most studies took place during infectious disease outbreaks: 10 during the COVID‐19 pandemic and one during an Ebola outbreak in Guinea. Other settings included surgical units (n = 3). Derks et al. (2018) was the only study to investigate thermal conditions at two different time points in a ward context with HCW in uniform without PPE. Most studies included nurses (n = 14) or doctors (n = 11) as participants.

TABLE 2.

Characteristics of included studies.

Author, year of publication	Countrya	Methodology	Setting	Participant healthcare profession
Bongers et al. 2022	Netherlands	Survey	General, medium, or intensive care COVID‐19 unit in metro hospitals	Physicians, nurses, NA, paramedics, nurse practitioners, physician assistants
Davey et al. 2021	United Kingdom	Survey	NHS metro hospital and other NHS settings	Nurses, PT, PT assistants, OT, medical students, junior doctors, consultants, surgeons, GP, radiographers, psychiatrists, dieticians
De Korte et al. 2022	Netherlands	Experimental	COVID‐19 ward in metro hospital	Nurses
Derks et al. 2018	Netherlands	Mixed methods	Two wards of metro hospital	Nurses
Grélot et al. 2016	Guinea	Observational	Metro healthcare center during Ebola outbreak	French nurses, auxiliary nurses, physicians
Hakim et al. 2018	United States	Observational	Metro children's hospital	Surgical and anesthesia trainees, student nurse, anesthetists, nurse anesthetists
Hunt et al. 2023	Australia	Survey	Metro hospital	Doctors, nurses, allied health professionals, phlebotomists, ward persons, students
Jegodka et al. 2021	Germany	Survey	Hospitals and healthcare homes	Nurses and nursing assistants
Karahan et al. 2022	Republic of Türkiye	Survey	COVID‐19 clinics of metro hospital	Nurses
Langø et al. 2009	Norway	Experimental	Metro hospital	Laparoscopic surgeon
Lee et al. 2020	India, Singapore	India and Singapore survey, Singapore exp. design	India: 10 hospitals in southern India, Singapore: general hospital ED	Medical, nursing, operations, sanitary, others
Messeri et al. 2021	Italy	Survey	Hospitals, mostly COVID wards	Doctors, nurses, other healthcare professionals
Palejwala et al. 2023	Australia	Experimental	Metro hospital	Surgeons, nurses, registrars
Tabah et al. 2020	Worldwide	Survey	Hospitals in 90 countries: 61% Europe, 16% Asia, 8% N. America.	Physicians, nurses, allied health professionals
Unoki et al. 2020	Japan	Survey	Hospitals	Nurses, physicians, allied health professionals

Abbreviations: ED, emergency department; Exp, experimental; GP, general practitioners; NA, nursing assistants; OT, occupational therapists; PT, physiotherapists; metro, metropolitan; NHS, National Health Service.

^a Location of research project.

3.3. Studies That Investigated Heat Stress Upon Healthcare Workforce

Table 3 summarizes the key features and findings of 13 studies that investigated the impact of heat stress on healthcare professionals (Bongers et al. 2022; Davey et al. ²⁰²¹; Derks et al. ²⁰¹⁸; Grélot et al. ²⁰¹⁶; Hakim et al. ²⁰¹⁸; Hunt et al.’s ²⁰²³; Jegodka et al. ²⁰²¹; Karahan et al. ²⁰²²; Lee et al. ²⁰²⁰; Messeri et al. ²⁰²¹; Palejwala et al. ²⁰²³; Tabah et al. ²⁰²⁰; Unoki et al. ²⁰²⁰).

TABLE 3.

Studies that investigated heat stress upon healthcare workforce.

Author, year	Description of study	Participant characteristics	Findings
Bongers et al. 2022	Survey investigating current experiences of HCW of heat strain during COVID‐19 pandemic (with PPE) and their recall of their experiences of heat strain before the COVID‐19 pandemic (without PPE).	N = 791, gender: 86% female, age: median age 32 (27–45) years, BMI 23.8 (21.6–26.7). Hours of sports activity per week: <1 h 22%, 1–3 h 55%, 4–6 h 21%, >7 h 2%.	HCW experienced approx. 25× more often heat strain symptoms working with PPE (93% HCW) compared to without PPE (30% of HCW; OR = 25.57 (95% CI = 18.17–35.98)). Female HCW and HCW <40 years were most affected by heat strain. PPE exposure time and sports activity level were not significantly associated with heat strain prevalence. Most common heat strain symptoms while wearing PPE: 79% thirst,78% thermal discomfort, 68% excessive sweating, 60% headache, 55% shortness of breath, and 39% reduced concentration.
Davey et al. 2021	Survey which assessed impact on health and wellbeing of HCW who were required to wear PPE during COVID‐19 pandemic.	N = 224, gender 86% female, age in years: 25% 18–29, 29% 30–39, 22% 40–49, 19% 50–59, 5% >60. Duration wearing PPE during shift in hours: 0–4 29%, 4–8 34%, 8–11 33%, >12 6%.	72% of respondents reported felt "hot", 90% felt "very uncomfortable" or "uncomfortable", and 99% felt they sweated more whilst wearing PPE. Top four heat related symptoms: 79% headache, 63% fatigue, 54% profuse sweating, and 40% dizziness. Most frequently reported cognitive tasks adversely affected when wearing PPE 60% attentional focus, 27% solving complex problems, 22% making decisions, and 20% retrieving information from short‐term memory. Content analysis of comments highlighted severity of heat‐related symptoms in vulnerable populations, such as menopausal women.
Derks et al. 2018	Study measured hospital ward thermal conditions and survey assessing thermal comfort perception of nurses at two time points: summer and autumn.	Summer: n = 89, gender: 64% female, age: 75% 21–30 years. Autumn: n = 43, gender: 77% female, age 53% 21–30 years.	Optimal thermal sensation for HCW was found to be closer to "slightly cool" than "neutral" on ASHRAE seven‐point thermal sensation scale. Survey found that both thermal conditions (20–25°C) led to an average self‐reported rating of "slightly warm" on ASHRAE scale—"slightly unacceptable" thermal comfort and "slightly obstructed" self‐appraisal work performance. All scores indicated significant discomfort from heat during summer data collection time point.
Grélot et al. 2016	Investigated thermal strain whilst wearing PPE using an ingestible thermal sensor during 2014 Ebola virus disease outbreak.	N = 25, gender 44% female, BMI: 10 females and eight males had BMI within normal range.	HCW wearing PPE exhibited moderate but safe thermal heat strain during shift of approximately 1 h. Mean working ambient temperature 29.6°C (2.0°C), relative humidity was 65.4% (10.3%). Mean time wearing PPE was 65.7 (13.5) min; and the mean core body temperature increased by 0.46°C (0.20°C). Four HCWs reached or exceeded a mean core body temperature of >38.5°C.
Hakim et al. 2018	Investigated operating room temp. on performance of clinical and cognitive tasks in three conditions: baseline 23°C, hot 26°C, and cold 21°C.	N = 22, gender 72% female.	Mean reaction time on the psychomotor vigilance testing was comparable for baseline, hot, and cold conditions. Self‐report scores of physical, mental, and temporal demands of task (range: 1–21): no significant difference found between baseline and cold conditions. Hot condition resulted in significantly lower self‐rated scores in physical demand and frustration.
Hunt et al. 2023	Survey investigated ED HCW during COVID‐19 pandemic. Workload assessed using National Aeronautics and Space Administration's task load index, thermal comfort assessed using five scales from the International Organization for Standardization; and Environmental Symptoms Questionnaire was used to assess subjective heat illness.	N = 59, gender: 53% female, mean age 33 years. (IQR 27–40), BMI of 25 (22–28) kg/m2., 54% wore "full" PPE and 39% wore partial PPE during their shift.	Workload not significantly different across gender, age, or BMI. Workload rated moderate to high across all subscales, with significant difference between doctors’ physical workload which was lower than other staff. 81% reported thermal sensation of slightly warm, warm, or hot, and 88% reported being uncomfortable, ranging from slightly to extremely. 58% desired to be slightly cooler or cooler, 73% reported being sweaty to some degree, 61% described conditions as slightly difficult to tolerate, and 97% reported at least one heat‐strain symptom. More than 50% reported light‐headedness or headache and approximately 30% reported feeling dizzy, faint, or weak.
Jegodka et al. 2021	Survey to investigate impact of hot weather upon HCW working in PPE.	N = 428, gender 82% female, 30.5% aged between 45 and 55 years.	96.5% of HCW found working in PPE during hot days "exhaustive". 93% reported breathing difficulties, and 86% concentration difficulties.
Karahan et al. 2022	Survey examined thermal comfort and sensation among nurses wearing PPE in COVID‐19 clinics. Body temperature and performance using 0–10 VAS, ASHRAE thermal sensation scale.	N = 246, gender: 76% female, age: mean 26.8 (5.5) years, BMI: 68% BMI in normal range. Mean daily working time in PPE was 10.5 (6.1) h.	Thermal comfort affected negatively while working in PPE: 59% of nurses complained about ambient temperature, 54% complained of poor ventilation, 29% complained of humidity, and 45% complained of poor air quality. Thermal comfort worse in ICU than other work areas. Respondents reported that working in PPE frequently caused sweating, breathing difficulty, fatigue, and thirst which affected their work performance after working less than an hour in PPE.
Lee et al. 2020	Survey which investigated heat stress and thermal perception of HCW during COVID‐19 pandemic in India and Singapore.	India N = 110, gender: 42% female, age: median 31 (26–38) years, BMI: median 24.4 (22.5–26.6) kg/m2. Singapore N = 55, 64% female, age: median 29 (27–33) years, BMI: median 22.0 (18.8–24.8) kg/m2.	In both countries, majority of HCW reported heat stress adversely affected productivity, clinical judgement, and emotions. 88% reported excessive sweating, 87% reported thirst, 78% reported exhaustion, and 84% desired to go to comfort zones. Significant differences between countries found in reports of air‐conditioning at worksite—Singapore 62%, India 25%; dedicated rest area availability—Singapore 100%, India 42%, PPE removal during breaks—Singapore 98%, India 60%.
Messeri et al. 2021	Survey which investigated heat stress associated with PPE during COVID‐19 pandemic. Survey adapted from Lee et al. 2020 survey.	N = 191, gender: 69% female, age: average 43 (11) years, BMI: 65% in normal weight range. Self‐reported work effort: 34% judged their work as moderate and 43% as high.	The impact of PPE on the thermal stress perception reported by participants was very high on body areas directly covered by PPE (78% of workers). Thermal sensation: slightly hot 11%, hot 36%, and very hot 53%. Reported symptoms from wearing PPE included thirst 58%, excessive sweating 71%, fatigue 46%, headache 43%, difficulty concentrating 29%, skin reaction 27%, and general discomfort 51%.
Palejwala et al. 2023	Investigated impact of two temperature conditions: HOT 30.8 C and CON (control) 24°C, on heat strain, subjective workload, and fatigue of surgical staff. 20‐point scales used for thermal sensation and thermal comfort.	HOT condition: n = 10, gender: seven females, mean age 45 years. CON condition: n = 7, gender: five females, mean age 50 years.	HOT condition resulted in heat strain (increased heartrate, core temperature, and fluid loss: p < 0.05), and increased subjective workload, discomfort, perceived exertion, and fatigue compared to CON conditions (p < 0.05). HOT conditions did not significantly affect manual dexterity or cognitive function (p > 0.05).
Tabah et al. 2020	Worldwide survey investigated PPE impact on HCW safety during COVID‐19 pandemic.	N = 2711, gender: 46% female, age: median 41 years.	Adverse effects were reported by 80%. 51% of respondents reported heat, 47% thirst, 28% headaches, 27% inability to use the bathroom, and 20% extreme exhaustion. Heat symptoms increased as hours of shift wearing PPE increased: 45% <3 h shift, 55% 3–5.9 h shift, 54% 6–8.9 h, 54% >9 h shift. Heat adverse effects at 3 h was highest adverse event.
Unoki et al. 2020	Examined impact of PPE on HCW in intensive care units during COVID‐19 pandemic in Japan.	N = 460, gender: 46% female, age: median 40 years.	75% of respondents reported wearing PPE caused them to experience intense heat. Respondents with significant heat symptoms more frequently used full‐sleeve waterproof gowns than those without this symptom (87% vs. 77.2%; p = 0.02).

Abbreviations: ASHRAE, American Society of Heating; Refrigerating and Air‐Conditioning Engineers; av, average; ED, emergency department; HCW, healthcare workers; PPE, personal protective equipment; temp, temperature; VAS, visual analogue scale.

Nine of these studies used surveys to investigate the impact of wearing PPE on heat stress during the recent COVID‐19 pandemic (Bongers et al. 2022, Davey et al. ²⁰²¹; Hunt et al. ²⁰²³; Jegodka et al. ²⁰²¹; Karahan et al. ²⁰²²; Lee et al. ²⁰²⁰; Messeri et al. ²⁰²¹; Tabah et al. ²⁰²⁰; Unoki et al. ²⁰²⁰). The surveys ranged from small surveys of 59 respondents (Hunt et al. 2023) to large surveys of 791 respondents (Bongers et al. 2022) and one worldwide survey of 2711 respondents (Tabah et al. 2020). Respondents in seven of these studies were predominantly female, except Unoki et al. (2020) and Tabah et al. (2020) who both reported a relatively even gender split of 46% female. Age and body mass index were commonly reported demographic information, with wide variation in both these demographics found between studies. Bongers et al. (2022) was the only study to record respondents reported engagement in physical activity per week. Eight of the nine studies surveyed healthcare professionals’ most recent experiences of heat stress whilst Bongers et al. (2022) compared healthcare professionals’ most recent responses working in PPE during the recent COVID‐19 pandemic to their recollection of how they felt working without PPE prior to the pandemic.

Five studies investigated workload as an outcome measure alongside thermal comfort and heat symptoms scales (Grélot et al. 2016; Hunt et al. ²⁰²³; Jegodka et al. ²⁰²¹; Messeri et al. ²⁰²¹; Palejwala et al. ²⁰²³). Hunt et al. (2023) found that healthcare professionals rated their physical workload from moderate to high but that doctors’ physical workloads were significantly lower than other healthcare professionals. These findings concur with the findings of Messeri et al. (2021) who found that over a third of respondents judged their work effort as either moderate (34%) or high (43%). Grélot et al. (2016) monitored heart rate during their study and found it reached “61% of the theoretical maximal heart rate” (p. 1463) during their study of approximately 1‐h duration. Likewise, a significant effect on heart rate and perceived exertion by staff in the operating theatre, with a theatre temperature of 30.8°C was reported by Palejwala et al. (2023). Consensus was found among studies that surveyed participants about their working environment with large percentages of respondents reporting uncomfortable ambient temperatures (58% Hunt et al. ²⁰²³; 59% Karahan et al. ²⁰²²; 68% Bongers et al. ²⁰²²). Hunt et al. (2023) also investigated thermal impact during occupational tasks using five scales measuring thermal comfort, sensation, preference, sweatiness, and tolerability from the International Organization for Standardization. Eighty‐eight percent of respondents reported being uncomfortable and nearly as many (81%) reported a warm thermal sensation ranging from slightly warm to hot (Hunt et al. 2023).

Consensus was found among nine studies on heat‐related symptoms reported whilst wearing PPE during the COVID‐19 pandemic. The symptoms included: sweating (68% Bongers et al. ²⁰²²; 99% Davey et al. ²⁰²¹; 73% Hunt et al. ²⁰²³; 88% Lee et al. ²⁰²⁰, headache (60% Bongers et al. ²⁰²²; 79% Davey et al. ²⁰²¹, 28% Tabah et al. ²⁰²⁰), fatigue (63% Davey et al. ²⁰²¹; 88% Karahan et al. ²⁰²²; 96% Jegodka et al. ²⁰²¹; 78% Lee et al. ²⁰²⁰), thirst (79% Bongers et al. ²⁰²²; 85% Karahan et al. ²⁰²², 87% Lee et al. ²⁰²⁰; 47% Tabah et al. ²⁰²⁰); and poor or reduced concentration (39% Bongers et al. ²⁰²²; 60% Davey et al. ²⁰²¹; 83% Jegodka et al. ²⁰²¹). Three of the studies found that some populations might be more vulnerable to heat stress than others, such as females (Bongers et al. 2022; Unoki et al. ²⁰²⁰) and females experiencing menopause (Davey et al. 2021).

One study used an ingestible thermal sensor to investigate thermal strain upon HCWs wearing PPE during the 2014 Ebola outbreak in Guinea (Grélot et al. 2016). Grélot et al. (2016) found that one‐sixth of their participants (n = 4) reached or exceeded mean core body temperature (38.5°C) during short shifts (average shift 66 min) working in the mean ambient temperature of 29.6°C and mean humidity of 65%. The rest of the healthcare professionals (n = 21) experienced moderate thermal strain considered by the authors of the study to be safe.

Two studies compared the impact of different temperature conditions during surgery on healthcare professionals (Hakim et al. 2018; Palejwala et al. ²⁰²³). Hakim et al. (2018) examined healthcare professionals’ performance of clinical and cognitive tasks in cold (21°C), baseline (23°C), and hot (26°C) conditions. Palejwala et al. (2023) assessed cognitive function, manual dexterity, and perceptual measures of staff whilst working in either 24°C or 30.8°C. Both studies found that increased heat had no effect on some of the objective outcome measures, including psychomotor vigilance testing (Hakim et al. 2018) and manual dexterity or cognitive function (Palejwala et al. 2023). However, Palejwala et al. (2023) found that the hot condition of 30.8°C resulted in significant changes to heart rate, core temperature, and fluid loss, indicating heat strain. Both studies found that the hottest condition impacted healthcare professionals' subjective scores including workload, discomfort, and fatigue.

Finally, Derks et al. (2018) explored nurses' experiences when working in standard uniform (no PPE) and their thermal comfort perception during autumn and summer (20°C–25°C). Significant discomfort from heat was found in all summer measurements and the authors reported they found the optimal thermal sensation for nurses working onward to be slightly cool using an American Society of Heating, Refrigerating and Air‐Conditioning Engineers (ASHRAE) seven‐point thermal sensation scale. Both thermal conditions led to an average self‐reported rating of “slightly warm” by nurses.

3.4. Studies That Investigated Mitigation Strategies That Healthcare Workforce Employed to Manage Heat Stress

Six studies investigated heat mitigation strategies for heat stress (Table 4) (Bongers et al. 2022; De Korte et al. ²⁰²²; Jegodka et al. ²⁰²¹; Langø et al. ²⁰⁰⁹; Lee et al. ²⁰²⁰; Messeri et al. ²⁰²¹).

TABLE 4.

Studies that investigated mitigation strategies that health workforce employed to manage heat stress.

Author, year of publication	Description of study	Participant characteristics	Mitigation strategies	Findings
Bongers et al. 2022	Pre‐ and post‐survey investigated HCW experiences of heat strain before (without PPE) and during COVID‐19 pandemic (with PPE). Examined availability and use of heat mitigation strategies.	N = 791, gender: 86% female, age: median age 32 (27–45) years, BMI 23.8 (21.6–26.7).	Focused on the following heat mitigation strategies: ice‐slurry ingestion, cold drinks, cooling vest, cold towel, ice cream, taking an earlier or longer break, and staying in cool room during breaks.	87% had one at least one heat mitigation strategy on their ward. Cold drinks (66%), ice slurry (41%), ice cream (30%), and cooling vests (25%) were most commonly available heat mitigation strategies. When available, cold drinks (82%), a cold room (76%), longer breaks (48%), more breaks (29%), and ice slurry ingestion (29%), were typically used four times per week. Cooling vests and cold towels were used less often.
De Korte et al. 2022	Examined impact of cooling vests upon perceived heat strain of HCW wearing PPE. Two working days tested: test 1 HCW wore cooling vest under PPE, test 2 HCW wore PPE with no cooling vest.	N = 17, gender: female n = 12, male n = 5, age: average 31(±8) years, BMI: average 24.9 (5.3).	Cooling vests: 36 phase change material inserts that had been cooled in refrigerator. Total weight = 1.2 kg.	Low ambient temperatures in both tests. Average sub‐PPE air temperature and RPE did not differ between both tests. Core temperature did not change in during two test conditions but reported thermal comfort and thermal sensation improved in the cooling vest versus control condition. 18% of nurses reported thermal discomfort when wearing a cooling vest versus 81% in the control condition.
Jegodka et al. 2021	Survey to investigate impact of hot weather upon HCW working in PPE.	N = 428, gender 82% female, 30.5% aged between 45 and 55 years.	Questions about behaviours undertaken to reduce heat stress during shift.	67% increased liquid intake. Very few respondents mentioned organisational support for employees during hot weather: 9% able to take more breaks, 9% change care planning to accomplish strenuous work during cooler hours. Less than 25% of staff receiving heat warnings and markedly less aware of heat protection plans.
Langø et al. 2009	Four phases of prototype design to improve surgeon's thermal comfort. (1) monitor temp. progression without cooling, (2) assessed commercial cool vest, (3) vest prototype designed, and (4) revised prototype.	N = 1, gender: male, age: 55 years.	Effect of cooling vest in surgical room temperature of 21–23°C.	Commercially available vest was unsuitable for surgery conditions. New prototype vest, post revision, resulted in cooling of body 2–5°C, improved moisture transport, and evaporation. Design included greater spacing between cooling elements to improve moisture permeability which resulted in decreased body temperature and increased thermal comfort.
Lee et al. 2020	Survey which included statements about heat mitigation strategies used by HCW during the COVID‐19 pandemic in India and Singapore. Singapore only pre‐ and post‐ thermal comfort ratings after ice slurry ingestion.	India N = 110, gender: 58% male, age: median 31 (26–38) years, BMI: median 24.4 (22.5–26.6). Singapore N = 55, gender 36% male, age: median 29 (27–33) years, BMI: median 22.0 (18.8–24.8).	Heat stress knowledge assessed in survey including knowledge of heat mitigation strategies: for example, pre‐hydration, ice slurry, and keeping fit. Singapore: ice slurry was provided to HCW to determine effect on thermal stress perceptions.	Majority of HCW agreed or strongly agreed with most statements about heat mitigation strategies. Except the following statements 26% strongly disagreed (SD) or disagreed (D) (25% neutral [N]) "drinking ice slurry will improve my heat tolerance", 37% SD or D (27% N) "heat stress can negatively affect commitment to the job", 26% SD or D (27% N) "keeping fit can improve heat tolerance". Singapore HCW: median thermal comfort rating improved from 2 (IQR 1–2) (warm) to 0 (IQR 0–1) (neutral) post ice slurry ingestion (p < 0.001).
Messeri et al. 2021	Survey which investigated heat stress and mitigation strategies associated with PPE during COVID‐19 pandemic. Survey adapted from Lee et al. 2020 survey.	N = 191, gender: 69% women. age: average 43 (±11) years, BMI: 65% normal weight range. Self‐reported work effort: 34% judged their work as moderate and 42.9% as high.	Questions about behaviours undertaken to reduce heat stress during shift.	Participants reported using the following heat mitigation strategies: drinking water 56%, taking breaks when able 42%, wearing light clothing 47%, prefer ventilated cool environment 34%, breathing techniques 15%, and ice‐cold drink 0.5%.

Abbreviations: HCW, healthcare workers; PPE, personal protective equipment; RPE, rate of perceived exertion; temp., temperature.

Of these studies, two assessed what heat mitigation strategies were available in workplaces and found that many workplaces did not offer heat protection strategies (Bongers et al. 2022; Jegodka et al. ²⁰²¹). Jegodka et al. (2021) found that 57% of respondents somewhat disagreed or strongly disagreed that more drinks were available. Four studies used surveys to assess what heat mitigation strategies were utilized by healthcare professionals during the recent COVID‐19 pandemic during their employment (Bongers et al. 2022; Jegodka et al. ²⁰²¹; Lee et al. ²⁰²⁰; Messeri et al. ²⁰²¹). Bongers et al. (2022) found 87% of healthcare professionals had access to at least one heat mitigation strategy, the most common were cold drinks (66%) and ice slurry (41%). A wide variety of heat mitigation strategies were reported to be in use by healthcare professionals in these studies including cold drinks (82% Bongers et al. ²⁰²²), increased fluid intake (67% Jegodka et al. ²⁰²¹; 56% Messeri et al. ²⁰²¹), cold room (76% Bongers et al. ²⁰²²). Interestingly, Lee et al. (2020) found that 51% of respondents either strongly disagreed, disagreed, or were neutral to the statement “drinking ice slurry will improve my heat tolerance”. However, in the Singapore arm of their research, which included an intervention of ice slurry ingestion, Lee et al. (2020) found a significant improvement in healthcare professionals' thermal comfort post‐ice slurry ingestion. The authors went on to suggest that pre‐cooling prior to shift may also be a useful strategy. The authors found that just over half (53%) responded with strongly disagreed, disagreed, or neutral to the statement “keeping fit can improve heat tolerance” suggesting a lack of knowledge from healthcare professionals on factors that influence heat mitigation. A lack of organizational support was also found. Jegodka et al. (2021) reported that less than a quarter of nursing staff working in outpatient care (24.1%) received heat warnings in their employment and even less (6.7%) were aware of heat protection plans.

Two studies conducted interventions using cooling vests (de Korte et al. ²⁰²²; Langø et al. ²⁰⁰⁹). Langø et al. ²⁰⁰⁹) used a participatory method to design a cooling vest for surgeons. This included a trial of a commercially available vest which was found to be unsuitable as it did not allow evaporation of sweat and restricted movement. Their resultant prototype vest cooled the surgeon's body between 2 and 5°C, improving thermal comfort, without restricting their ability to move. De Korte et al. (2022) examined the impact of cooling vests upon perceived heat strain in a small population of 17 nurses during the recent COVID‐19 pandemic. Two conditions were investigated: test 1: cooling vest was worn under PPE, and test 2: PPE with no cooling vest. Results found no differences between test conditions (ambient air temperature, sub‐PPE air temperature, and rate of perceived exertion) but thermal comfort and thermal sensation were significantly improved in the cooling vest test condition.

Only one study identified facilitators to heat mitigation strategies. Langø et al. ²⁰⁰⁹) identified that cooling vests needed to be close‐fitting to allow adequate freedom of movement. They concluded that in contrast to the cooling vests made for other emergency professionals, such as firefighters, vests for healthcare professionals should be made of thin permeable material to allow heat exchange and moisture transport. They also recommended that healthcare professionals should be provided with synthetic fiber, sports‐style shirts to wear beneath cooling vests to draw moisture away from the body.

Several barriers to heat mitigation strategies were identified. PPE was identified as a barrier to heat mitigation strategies by several authors (Jegodka et al. 2021; Lee et al. ²⁰²⁰; Messeri et al. ²⁰²¹). Lee et al. (2020) pointed out that the impact of PPE upon healthcare professional's ability to engage in heat mitigation strategies was further compromised in developing countries where access to PPE might be limited, leading healthcare professionals to conserve and reuse their PPE. A lack of institutional support and knowledge (Jegodka et al. 2021; Lee et al. ²⁰²⁰; Messeri et al. ²⁰²¹), and the busy schedules of healthcare professionals (Lee et al. 2020; Messeri et al. ²⁰²¹) were also identified as barriers to heat mitigation strategies. Langø et al. (2009) pointed out that cotton, the material that large numbers of healthcare professionals’ uniform is made from, does not absorb sweat, increasing healthcare professionals’ discomfort.

4. Discussion

This review examined the current evidence exploring the impact of heat stress on healthcare professionals and mitigation strategies employed to address it. The review found only 15 studies conducted over a 14‐year period investigating the impact of heat stress in healthcare professionals. This contrasts to a larger body of research relating to other, mainly outdoor occupations such as agriculture, construction, mining, and utility workers (Habibi et al. 2021; Ioannou et al. ²⁰²²; Moda et al. ²⁰¹⁹). Thus far, the small number of studies investigating the impact of heat on the health workforce has focused mainly on two health occupational hospital contexts: treating infectious patients whilst wearing PPE, and surgical contexts. Surgical contexts may combine wearing PPE and working in hotter temperatures due to particular patient populations, such as pediatrics (Hakim et al. 2018) or patients with significant burns (Palejwala et al. 2023) who are at risk of hypothermia during surgery. Fourteen out of the 15 studies included in this review were focused on healthcare professionals’ heat responses related to the use of PPE in the above‐mentioned contexts. This focus is perhaps unsurprising given the recent COVID‐19 pandemic and increased risk of heat stress for healthcare professionals wearing PPE as protective clothing reduces a worker's ability to lose heat (Daanen et al. 2020). However, it should be noted that not all healthcare professionals work in hospital‐like regulated indoor environments. Healthcare professionals also work in communities, visiting people in their homes, and may travel and move through multiple settings as part of their occupation, thus having very little control of the spaces or the temperatures in which they work.

Findings from this review revealed that some studies overlooked the contribution of workload on healthcare professionals experience of heat stress. Workload is an important consideration because higher physical workloads increase the thermal burden experienced by the worker (Ioannou et al. 2022). Studies that investigated workloads of healthcare professionals as part of their research found large proportions of healthcare populations self‐rated their workloads from moderate to high (Hunt et al. 2023; Messeri et al. ²⁰²¹; Palejwala et al. ²⁰²³). These findings concur with recent research using accelerometers which found that emergency nurses in Australia engage in occupational physical activity of moderate to vigorous intensity during their shift (Chappel et al. 2020). Healthcare professionals are a heterogenous occupation group with highly variable roles leading to a wide variety of physical workloads between and within different healthcare professions. For example, Hunt et al. (2023) found that doctors’ physical workloads were less than other healthcare professionals in emergency and critical care units in a hospital setting in Brisbane, Australia. Taken together these findings suggest that future research should investigate the impact of physical workload amongst a wide variety of healthcare professions, in a larger variety of contexts, to inform future development of policy and mitigation strategies on heat stress.

Large proportions of healthcare professionals reported high levels of thermal discomfort and desired a cooler temperature in their workplace. As already stated, most studies related thermal discomfort to healthcare professionals use of PPE, but it is important to note one study that found significant thermal discomfort in nurses working during summer temperatures (25°C) whilst wearing their usual uniform and no PPE (Derks et al. 2018). They reported that using ASHRAE seven‐point thermal sensation scale, healthcare professionals appeared to prefer slightly cool working conditions (Derks et al. 2018). This preference, if replicated by future studies, presents a challenge to future healthcare policy and management.

Climate change is predicted to increase summer temperatures in many parts of the world well over 25°C (Levi, Kjellstrom, and Baldasseroni ²⁰¹⁸; Hall et al. ²⁰²²). Working in high heat levels has been found to impact non‐healthcare workers' health and productivity (Flouris et al. 2018; Varghese et al. ²⁰¹⁸) and this review demonstrates that further evidence is required to explore these impacts on health workers. Mechanisms to build climate‐resilient health systems have been published by the World Health Organisation (2015, n.d.) but maintaining a comfortable occupational temperature for healthcare professionals is complex and complicated by balancing the temperature needs and well‐being of patients, who are mostly sedentary, alongside that of the health workforce, whose workloads can be of high intensity. Thus, the key engineering control of manipulating healthcare professionals’ occupational temperature is more challenging than other indoor occupational settings, such as offices (Yuan et al. 2022). The current paucity of research to support and help healthcare professionals in this space suggests that the needs and well‐being of healthcare professionals are in danger of being overlooked. Perhaps this is in part due to some consensus in the literature that suggests working in uncomfortably high heat conditions does not affect healthcare professionals’ cognitive function, manual dexterity, or transfer into negative patient outcomes (Hakim et al. 2018; Palejwala et al. ²⁰²³). However, these findings should be treated with caution, as they are drawn from small populations and relate to short‐duration operating theatre conditions. Findings from other industries suggest that professionals experiencing heat‐related symptoms are more likely to work at a reduced capacity (Amoadu et al. 2023). This may be occurring amongst healthcare professionals in non‐surgical contexts as many are reporting fatigue as well as other heat strain symptoms.

Studies included in this review reported a variety of heat strain symptoms in health professionals including sweating, headache, fatigue, thirst, and poor or reduced concentration. The reported heat strain symptoms in included studies concurred with those reported in other industries, such as mining and agriculture (Habibi et al. 2021). Long‐term heat strain has been found to negatively impact non‐healthcare workers’ health and well‐being (Ebi et al. 2021). Some populations are known to be more vulnerable to heat stress. For example, a recent review identified low fitness and aerobic capacity, low body mass, and lack of heat adaption as key vulnerability factors to heat stress (Foster et al. 2020). In the current review, few insights were gained into sub‐populations of healthcare professionals that may be at greater risk of heat stress. For example, only one study investigated physical activity status. Bongers et al. (2022) asked participants to divulge how much sports activity they participated in per week. However, it should be noted that the population of their study was 86% female. Sports activity is only one type of physical activity and women are less likely to participate in sport than men (World Health Organization n.d.a). Given the importance of aerobic capacity in coping with heat (Alhad, Tan, and Lee ²⁰¹⁹), future studies should include measures of physical activity that are more inclusive, thus providing a more accurate measure of healthcare professionals’ aerobic capacity. A recent review on gender responses to heat stress concluded that being female was likely less impactful as a vulnerability factor in heat stress than fitness or age (Foster et al. 2020). Thus, future research focused on the impact of heat on the healthcare workforce should consider initially focusing upon gender‐inclusive vulnerability factors. The current review included three studies that found gender differences in response to heat stress (Bongers et al. 2022; Davey et al. ²⁰²¹; Unoki et al. ²⁰²⁰). These studies did not adequately address the above gender‐inclusive vulnerability factors that Foster et al. (2020) had identified. However, given that health occupations, particularly nursing and allied health professions, tend to be female‐dominated professions (Shannon et al. 2019) and there is evidence globally that women across all age groups tend to be less active than men (World Health Organization, n.d.b), the interplay of these factors with gender (and culture) may need further consideration in preparing healthcare professionals to cope with working in heat.

Most of the mitigation strategies investigated by the small number of included studies were individual control strategies with very little focus on engineering or managerial controls. The wide variety of individual mitigation strategies in use concur with those used in other occupational industries (Amoadu et al. 2023). However, controls that work in other industries such as mining may not work in healthcare due to contrasting context and funding models. It is concerning that managerial controls have not been widely investigated in healthcare and when they have been used as a survey item, some may be unrealistic for healthcare professionals to adopt. For example, the suggestion to take more frequent or longer breaks may not be a realistic work strategy for busy healthcare professionals during a pandemic, especially when their health organization has not adopted it as part of their heat policy (Jegodka et al. 2021). Policies where health organizations employ more staff during hot and busy periods, enabling staff to work at a steadier pace and reducing their workload intensity, may arguably be a more realistic solution. Likewise, further investigation into uniforms made from materials that absorb sweat more effectively than cotton‐based uniforms, may increase healthcare professionals’ comfort (Langø et al. 2009). Very few facilitators or barriers to heat mitigation strategies were identified by the included studies. Future research should investigate a broader range of mitigation strategies whilst acknowledging that in many areas of health elimination and substitution controls may not be viable options due to the impact on patient's populations. However, there is a need to investigate all levels of controls such as engineering and managerial, as well as personal controls, to gain greater insights into how to tailor them for individuals, and their facilitators and barriers.

Finally, 14 studies included in this review were based in high Organization for Economic Co‐operation and Development (OECD) countries, and one study based in Guinea focused on participants from France, another high OECD country, who were working in the Guinea area (Grélot et al. 2016). Future research must consider the implications of heat on healthcare professionals in lower OECD countries as well. This is important as they are substantially more vulnerable to the impacts of heat and climate change will disproportionately affect those in lower OECD countries (Odeku 2022).

Studies in this review were predominantly survey‐based and small numbers of intervention studies signal the relatively new emergence of this research area in health. The heterogeneity of questionnaire scales used, and the low methodological quality of some studies made it difficult to compare across studies and draw useful guidance from them. The survey‐based studies also did not capture information on the environment or setting of the respondent to allow for meaningful exploration of the impact of different settings on heat mitigation (i.e., air‐conditioned settings vs. outdoor/unconditioned settings). Participatory approaches could be considered to enhance the efficacy of heat mitigation strategies for healthcare professionals. Only one study in this review utilized this approach (Langø et al. 2009). Adopting this approach in future research would leverage the knowledge of health workforces, particularly in relation to their role, environment, and physical workload. However, researchers should not assume that all health professionals have knowledge of heat stress and mitigation strategies as studies included in this review found that health workforce populations may require further education in this space (Lee et al. 2020). Finally, this review was limited to studies published in English between the years 2009 and 2023.

5. Conclusions

The limited amount of literature, narrow scope of health occupational contexts studied, and reliance on survey methodology found in this review show that a greater understanding of the impact of heat stress upon healthcare professionals and mitigation strategies that are effective in their unique occupational context is needed. Healthcare professionals are a diverse occupational group who work across many settings, but most have to consider either the well‐being of largely inactive patient populations (thus different thermal requirements) or have little control over the environment in which they work. Future studies should adopt a more comprehensive approach to investigating healthcare professional's experiences, investigating all levels of controls, as healthcare professionals will find it hard to adopt mitigation strategies that are not supported or provided by their workplace.

Appendix A. Databases and search strategy.

A.1.

EBSCOhost: Academic Search Complete, CINAHL Plus with Full Text

ProQuest: Health & Medicine Databases (MEDLINE, Health & Medical Collection, Nursing & Allied Health Database, Psychology Database), ProQuest Dissertations & Theses Global

Ovid: Ovid Emcare

Informit Health Collection

Example search string

(Thermal OR heat OR occupation*) AND (stress OR strain OR illness)

AND (health* OR medic* OR nurs* OR clinical OR (social work) OR allied OR paramedic*)

All in title

Filters: 2009–2023, English language, Peer reviewed

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.