The Impact of Climate Change on Cognitive Performance among Workers: A Systematic Literature Review

doi:10.21203/rs.3.rs-3201732/v1

Due to climate change and global warming, attention-demanding tasks, continuous performance tasks, choice reaction time and vigilance tasks have become less efficient, which can, directly and indirectly affect cognitive performance, specifically among workers exposed to hot-dry and hot-wet environments.

This systematic study was done by reviewing research studies on the impact of climate change on cognitive performance and gathering physiological responses that can increase vulnerability to climate-related cognitive performance among workers. In this study, a total of 3487 articles from experienced worker population (men = 574; women = 94) in various real-world environmental and experimental climate conditions were searched.

Climate change causes the most significant decrease in cognitive performance, especially in attention-demanding tasks. Decreasing vigilance performance in hot seasons is one of the outcomes of global warming. The effect of high temperature and heat stress on cognitive performance correlated with changes in physical parameters (air temperature, relative humidity (RH), etc.) and physiological parameters (core-body and skin temperature, heart, breathing, and sweating rate, etc.).

It is required to develop more studies, especially in various real-world environments, and develop a framework to strengthen workers’ awareness for considering the impact of climate change on cognitive performance among workers. The present study results can be used to inform policy-makers with physiological parameters and upper limit values for occupational exposure to thermal stress.

Systematic Review

Climate Change

Thermal Stress

Cognitive Performance

Workers

Climate change is becoming a danger to human well-being, especially for workers in many job situations with warm climate conditions (1). Exposure to extreme thermal stress and hot environments exhibit workers at risk of heat, causing heat-related outcomes such as heat cramp, heat stroke, heat syncope, and even death (2). High temperature-induced dysfunction of the neuromuscular system, aerobic system, central nervous system (CNS) function, and cognitive dysfunction (3). The high temperatures produced robust effects on hormones and mood (i.e., decreased catecholamine and increased fatigue) (4). Excess heat at work environment can also affect body metabolism, core body temperature, heart and breath rate, and blood pressure and may cause thermal discomfort, illness, and an increase in human errors and ultimately accidents (5). Accordingly, the physiological reactions of body to thermal stress has been well identified, but the effect of global warming on perceptual performance of workers are not well understood although many experimental studies in this area have been conducted (6). Diminishing cognitive ability of human in hot environments is well evident, but physiological and perceptual response changes have a higher tolerance threshold. Therefore, in jobs with some degrees of cognitive reactivity, workers already exposed to thermal stress should be prohibited from work, since it can affect their cognitive performance (7). Threshold limit values of exposure to thermal stress in hot environments have been developed based on physical, physiological, and medical criteria (8). For convincing reasons, it is necessary to assess the effects of heat stress in hot environments based on cognitive abilities (9). Understanding the effect of climate change and heat stress on cognitive and perceptual functions cannot help to determine the threshold limit value, but it can lead to the improvement of the quality of social life and workplaces (10). There is also a positive correlation between thermal discomfort and unsafe behaviors of workers (11). Therefore, in order to increase safety in the workplace, it is very important to evaluate the cognitive and psychomotor performance of workers, especially in warm workplaces and hot seasons of years (12). Also, the increase in industrial and occupational complexities in the current world and the existence of global warming has caused an increase in the burden of mental imposed on human operators, leading to an increase in human error (13). The focus of new interactions between technology and humans has been on prevention of human errors. The analysis of cognitive performance under thermal stress to determine the standard design of the workplace or workstation is very significant, since a large part of the task has a cognitive nature (14). In general, few research studies have investigated the impact of climate change on cognitive performance under heat stress conditions, and there is little knowledge in this field. There have been many challenges to creating a threshold limit value for cognitive performance based on physiological performance. This study was conducted to gather various impacts of global warming and climate change on cognitive performance among the working population.

Search

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) (15) was used to conduct this systematic review. Scientific databases such as Scopus, Web of Science, and PubMed were investigated to identify related published research studies until October 2022. To develop search syntax the synonyms related to ‘climate change’ and ‘cognitive performance’ were identified using PubMed Mesh system, research team, and specialist opinion. The search strategy was finalized by Number Need to Read (NNR) index in Scopus and conducted in title, abstract or keyword fields in databases. The conference papers and key journals were investigated to find more relevant studies through Scopus database. Four key journals including the Urban Climate, International Journal of Environmental Research, Applied Ergonomics, and International Journal of Biometeorology were investigated. References of the included articles wereinvestigated by hand-searching. Following search strategy was used in this study:

TITLE-ABS-KEY("Cognitive performance" OR "Cognitive function*" OR Cogniti* OR "Cognitive skill*" OR "Cognitive abilit*" OR "Cognitive capacit*" OR Perception OR "Cognitive alteration*" OR Awareness OR Alertness OR consciousness) AND TITLE-ABS-KEY("climate change*" OR (climate AND chang*) OR "extreme weather*" OR "extreme heat" OR "hot day*" OR “high temperature*” OR “extreme temperature*” OR “global warming” OR “hot environment*” OR “heat stress” OR “heat strain” OR “thermal stress” OR “Hot-dry” OR “Hot-wet” OR “Relative humidity” OR “heat wave”) AND TITLE-ABS-KEY(worker* OR workplace* OR personnel OR Employee* OR operator* OR Employment OR “Shift work”)

Inclusion criteria

The “PICO” components were used for systematic exploratory review: P (workers), I (climate change), C (cognitive performance), and O (cognitive performance reduction).

Studies were included if they were (a) conducted on female and men workers; (b) about extreme heat, hot days, high temperature, extreme temperature, global warming, hot environment, heat stress, heat strain, thermal stress, hot-dry and hot-wet climate conditions; (c) conducted on the effect of climate change or global warming on cognitive ability; and (d) conducted on working-age population (about 18–65 years) when facing warm process and climate change.

Studies were excluded if they were (a) on hydration and cognitive function among the general population; (b) conducted on the elderly, recruited from local high schools and also children's cognitive performance; (c) evaluated the effect of climate change on cognitive performance in animal models; and (e) without full-text studies.

Screening, selection, and data extraction

All the identified studies were transferred to EndNote, subsequently duplicated studies were deleted. Screening by title and abstract was done by one of the researchers (AH), then two reviewers (PH and AH) investigated the full-text of studies independently and extracted data through reviewing eligible studies. Disagreement between the two reviewers on included or excluded studies, were resolved by research team consensus and discussions.

Quality appraisal

The methodological quality of selected studies was investigated by two reviewers (PH and AH) independently using Quality Assessment Tool (QATSDD), that is a reliable and valid tool to assess the quality of research studies (16). Any disagreement about quality score was resolved through research team consensus.

Search results

The detailed procedure of screening and selection phases is shown in Fig. 1. The primary search resulted in 3487 studies (Web of Sciences = 1329, Scopus = 1948, and PubMed = 210). After screening title and abstract, 76 studies were remained for full-text investigation. Finally, 21 studies were selected for data extraction. Through key journals searching, any relevant articles were found for data extraction. After hand-searching of eligible studies references, four relevant articles were found. Totally, 25 research studies were investigated regarding the effect of global warming and climate change on perceptual performance. The characteristics of the selected articles are shown in Table 1. Sixteen experimental studies directly manipulated thermal stress combined with cognitive performance. Another study was a cross-sectional research, investigating the impact of thermal stress on cognitive performance in hot-humid and hot-wet days of ambient temperature. Most studies reported thermal stress via climate conditions, with dry temperatures (between 26°C and 50°C), relative humidity (RH) (ranging 19–65%), and Wet Bulb Globe Temperature (WBGT) (ranging 25–35°C). In many studies, physiological responses such as skin temperature, core body temperatures, heart rate and Peak Oxygen Uptake (V̇O₂ peak) were recorded; however, the physiological responses were different in time points. Acclimatization to heat in workers was only reported in limited studies.

Table 1. Characteristics of the included studies examining the impact of climate change on cognitive performance among workers

The studied group	Author/year and country	Type of document	Participants	Climate conditions	Cognitive performance test	Physiological responses	Impact of Heat Stress	Outcome	Quality rating
Workers	Mazloumi et al., 2014 (Iran) (17)	Cross-sectional	70 M/ Malibel Saipa Company, 35 Case, 35 control	Control (WBGT= 16.75-35.4℃) Case (WBGT= 30.8-32.6℃)	SCWT (reaction time, accuracy, and attention)	NA	Test duration Reaction time Number of errors ***	Heat stress can lead to dysfunction of perceptual abilities, such as selective attention and reaction time.	34
	Mazloumi et al., 2014 (Iran) (18)	Cross-sectional	70 M/ Automobile factory, 35 Cases, 35 control	Control (WBGT= 16.75) Case (WBGT= 30.81-35.41℃)	SCWT (reaction time, accuracy, and attention)	Stress hormones (Cortisol*; Adrenaline; Noradrenaline***)	Test duration Reaction time Number of errors ***	Heat stress can increase impairment in cognitive performance and stress hormones in blood	24
	Golbabaei et al., 2014 (Iran) (19)	Cohort	70 M/ Hot industry, 35 Case , 35 control	Control (WBGT= 16.7) Case (WBGT= 33℃)	SCWT (reaction time, accuracy, and attention)	NA	Test duration* Reaction time * Increasing frequency of errors *** Stroop test 3	Heat stress can lead to increase the reaction time and decreasing selective attention.	24
	Fine et al., 1978 (U.S.A.) (20)	Cross-sectional	30 M, Artillery fire direction center operations	35°C and 88% RH, 7h	Complex cognitive tasks	NA	Increasing the number of omission errors rather than commission errors.	Exposing to heat stress affects most of tasks	32
	Furtado et al., 2007 (U.S.A.) (21)	Cross-sectional	12 M, Power industry	WBGT= 32.2–37.8 °C	Subjective responses, productivity, and error rates	Heart rate* Oxygen consumption* Tympanic temperature	Productivity* Subjective responses* Error rate***	Heat stress on outdoor workers leads to fatigue and subsequently deterioration in doing tasks	32
	Chen et al., 2003 (Taiwan) (22)	Cross-sectional	55 M, Electric arc melting workers	WBGT=25.4∼28.7°C and 30.0∼33.2°C	Fatigue, eyes feel strained, and critical flicker fusion	Heart rate Systolic pressure	Critical flicker fusion^{N. S.}	Exposing to hot workplace environment leads to workers fatigue.	30
	Berg et al., 2015 (U.S.A.) (23)	Cross-sectional	21 M, Laparoscopic operative tasks ( Surgeons)	19 and 26°C	SURG-TLX	NA	Intracorporeal knottying tasks^{N. S.}	Hot condition leads to distraction on the score of SURG-TLX among operators.	30
	Morley et al., 2012 (USA) (24)	Experimental	29 M Firefighters	Ta= 33–35°C	Neurocognitive tests( short-term memory), sustained and divided attention, and reaction time	Heart rate* Rectal temperature*	Short-term memory * Reaction time*	Neurocognitive tests and reaction time have been detected higher than one hour after exercise	28
	Hocking et al., 2001 (Australia) (25)	Experimental	Military operations	Ta= 25–35°C, RH=65%	Brain electrical activity and psychometric test batteries	Heart rate** Rectal temperature**	Psychometric task performance*	Hostile environments can induce a high sensitivity of brain imaging techniques in cognitive performance.	30
	Lan et al., 2011 (China) (26)	Experimental	6 M and 6W Office work	Ta= 22 and 30°C	Neurobehavioral tests, Raw TLX, and tasks typical of office work	Heart rate** Skin temperature	Performance Mental demand	There is a negative effect on cognitive performance when people feel thermally warm.	30

Volunteers ( working-age population)	Wyon et al., 1979 (Sweden) (27)	Experimental	36 M and 36 W	20—29°C, three successive periods of 50 min with 10-min breaks between	Sentence comprehension, Recognition memory	NA	Sentence comprehension * Multiplication task * Recognition memory*	Moderate heat stress leads to reducing arousal in the absence of conscious effort.	25
	Nunneley et al., 1979 (U.S.A.) (28)	Experimental	9 M	Control ( T_{d b}=25) Case (WBGT= 31 and 35℃)	Compensatory tracking task	Heart rate ^{N. S.} Rectal temperature ^{N. S.}	Simplest tracking task * Two more difficult tasks ^{N. S.}	Heat stress can lead to no change in tracking-task execution in cockpit condition simulation	28
	Azer et al., 1972 (U.S.A.) (29)	Experimental	21 M	32.2,35 and 37.8 ℃ with RH= 50, 75 and 50% respectively	Compensatory tracking task and peripheral task	Skin temperature^{N. S.} Rectal temperature* Heart rate^{N. S.} Weight loss rate^{N. S.}	Reaction time *	The performance was not significantly affected by 3 of climate conditions.	30
	Fraser et al., 1955 (U.S.A.) (30)	Experimental	7 M	47.2℃, RH= 50%	Simple reaction time and complex reaction times	NA	Simple reaction time*	Experiment showed a negative correlation between simple reaction time and hot workplace environment.	28
	Hygge et al., 1991 (Sweden) (31)	Experimental	32 M and 32 W	19 and 27°C	Mental arithmetic, a recognition task, hidden figures test, proofreading, verbal fluency, and serial reaction task	NA	Hidden figures test*	There is antagonistic interaction between exposure to heat stress and hidden figures test. Hot workplace environment leads to increase the rate of response without increase the rate of errors.	28
	Provins et al., 1970 (Australian) (32)	Experimental	20 M	WBGT= 35-40℃	Visual vigilance task and SRT	Oral temperature***	Central SRT task* Peripheral vigilance task*	Heat stress can affect perceptual-motor performance by a change in body temperature.	30
	Sharma et al., 1986 (India) (33)	Experimental	8 M, Heat-acclimatized subjects	Hot Dry ( T_{d b} =45°C , RH=30% ), and Hot Humid ( T_{d b} =39°C, RH= 60% ) at WBGT= 34°C.	Concentration test and psychomotor rest	Level of dehydration*	Under hot- humid conditions ( Level of dehydration*) Under hot- dry conditions( Level of dehydration*) Routine mental work^{N. S.}	in hot and humid environments more pronounced concentration component was obvious	28
	Taber et al., 2011 (Canada) (34)	Experimental	5 M and 6 W Helicopter escape procedures	23 °C and RH= 40% , 34 °C and 35%	Psychomotor skill (HUET) performance	Rectal temperature* Skin temperature Heart rate	Performance of HUET skill^{N. S.}	Heat stress cannot deficits in escape efficiency that expected in the first time of flight.	32
	Gaoua et al., 2011 (Qatar) (35)	Experimental	11 M and 5 W	CON: 20°C and RH= 40%, Hot: 50°C and RH= 50%	Cognitive testing ( test battery), attention tests, and memory tests	Rectal temperature* Ttymp* Thead***	Cognitive testing**	Heat stress exposure can impair workers memory but does not affect simple attentional processes.	32
	Cheuvront et al., 2004 (USA) (36)	Experimental	7 M	Ta= 40°C, RH= 20%	Cognitive testing ( test battery)	V̇O₂peak Blood Analysis**	RPE**	Cognitive performance does not alter exerciser in the heat stress exposure when subjects are hypohydrated.	30
	Tomporowski et al., 2007 (USA) (37)	Experimental	11 M	Ta= 30 °C; RH= 40 %	Executive-processing test and short-term memory test	V̇O₂ peak Rectal temperature Skin temperature Heart rate	Cognitive testing RPE	Exercise -induced dehydration influence participants' performance in exposure to heat stress,.	32
	Witterseh et al., 2004 (Denmark) (38)	Experimental	16 M	Ta= 22/26/30°C RH= 45%, 35% and 28%	Tsai–Partington test, creative thinking, and text typing	NA	Tsai–Partington test Creative thinking Text typing***	Hot weather can increase subjective distress and fatigue.	30
	Færevik et al., 2003 (Denmark) (39)	Experimental	8 M, Wearing aircrew protective clothing	Ta= 0°C ; RH= 80%, Ta= 23°C; RH= 63%, and Ta= 40°C; RH= 19%	Cognitive variables (incorrect reactions, missed reactions, and reaction time)	At 40°C : Rectal temperature* Skin temperature* Heart rate* Sweat production* V̇O₂ peak*	At 40°C : Cognitive variables**	Cognitive ability is virtually vulnerable to heat stress that cause changing in core body temperature.	32
Athletes	Sunderland et al., 2005 (UK) (40)	Cross-sectional	9 W, Unacclimatized hockey player	Hot (30°C, RH= 38% ) and moderate (19°C, RH= 51%)	Skill performance, decision-making, fifteen-meter sprint times	In the hot environment, Rectal temperature ** Perceived exertion * Perceived thirst ** Blood glucose concentration * Serum aldosterone concentration ** Sweat rate *	In the hot environment, Performance* Decision-making Fifteen-meter sprint times	Field hockey-players showed diminished skill performance in greater environment temperatures in the hot environment conditions.	30
Athletes	Bandelow et al., 2010 (Turkey) (41)	Cross-sectional	20 M, Football player	33-34°C, RH= 62-65%	Cognitive functions, visual sensitivity	Core temperature * Plasma osmolality Glucose levels	Visual sensitivity* Cognitive functions***	Increasing in core body temperature leads to decreasing glucose in blood and leads to diminished faster and also leads to less accurate performance	30

SCWT = Stroop Colored-Word Test; WBGT = Wet Bulb Globe Temperature; M = Male; W = Women; (P = 0.1)*; (P = 0.01)**; (P = 0.001)***; (P = 0.0001)****; T_{d b}= Dry Bulb Temperature; RH = Relative Humidity; N. S. =Not Significant; SRT = Serial Reaction Time; SURG-TLX = Surgical Task Load Index; HUET = Helicopter Underwater Escape Preparation And Task Performance; Ttymp = Tympanic Temperature; Thead = Forehead Temperature; V̇O₂ peak = Peak Oxygen Uptake; RPE = Perceived Exertion; Raw TLX = Mental workload.

Descriptive analysis

In this systematic review 25 relevant studies were reviewed, and most of results showed that climate change can affect cognitive performance among workers. Negative impacts of hot work environment on cognitive performance in the future workplaces, climate change will affect physiological and perceptual parameters, particularly in hot seasons. From 25 assessed studies, 10 studies (40%) directly investigated the effect of global warming or climate change on cognitive performance in workplace in different countries (Iran, Australia, USA, China, and Taiwan). Two papers (8%) conducted the effect of climate change on skill performance and decision-making among athletes in countries (UK and Turkey). Many studies (52%) were conducted on working-age population (about 18–65 years), especially in laboratory climate conditions showed that exposure to climate change-induced thermal stress is associated with cognitive performance in different countries (Sweden, Australia, USA, India, Canada, Qatar, and Denmark). Overall, the results of investigating the included showed the impacts of climate change on cognitive variables (such as incorrect reactions, missed reactions, and reaction time). Finally in order to classify the results of reviewing included studies, data abstraction was conducted based on keywords. The selected studies were classified into parameters with major themes that include physiological responses and impact of thermal stress on cognitive performance among workers population (21).

Thematic content analysis

This study summarizes evidence published on the subject of the effect of climate change on cognitive performance among workers. Studies have revealed that exposure to thermal stress due to climate change is associated with negative physiological responses and cognitive performance impacts. The main physiological parameters impacts of climate change include increase in core body temperature, skin temperature, heart rate, sweat production and V̇O₂ peak, and impairment of mental and physical performance (21, 23, 40, 41).

The impact of climate change on the work performance

Tasks that require paying more attention and prompt reactions were significantly affected by thermal stress. Reaction time was worsened with high hot-wet and hot-dry climate conditions, and did not change in low and moderate thermal stress (42, 43). Li et al. demonstrated that faster simple reaction time during the mead time was at 40°C compared to natural temperature at 25°C of pilot performance (44). Choice stepping reaction times were improved or unaffected at 30°C (35, 45). Also, wearing protective clothing when exposed to high temperature around 40°C, showed an increase on physiological variables (heart rate, skin and core body temperature, and dehydration degree) and caused increasing errors in various tasks (39). Declined performance was shown in simple operation while considering accuracy (by 7% at 30°C for 4.5 hr).It was the fastest at 29°C than at 23°C, and 26°C in exposure to warm climate conditions compared to 29°C and 23°C (26). There is an increase in core body temperature improved (range of 1°C to 2°C ) and rapid visual processing (RVP) during exposure to passive thermal stress (46). In a hot environment (50°C) that core body temperature was high (1.5°C), there were no effects on reaction time task among workers (35). Working memory tasks impaired when heat stress was severe (17). Digit span performance was not affected by climate conditions (in 30°C to 35°C ) (26), or increased in cases that environment temperature is more than skin temperature and core body temperature (47). Performance on spatial recall tasks and verbal working memory was not affected at 36°C, as was performance on the matching-to-sample (ambient temperature 40°C to 50°C) task (48). Adaptation to exemplar task performance was not affected by hypohydration and acute thermal stress (45). When climate conditions were 4°C above an individual's optimal temperature, participants rated their performance as better although performance on a word memory task was further unaffected (48). Correct parameters on a word recall and memory retrieval task decreased at 30°C to 44°C, and number of the postgraduate memory scale reduced at 42°C when living in hot temperature compared to 27°C (49, 50). A study examined the impact of thermal stress-induced dehydration on cognitive performance in acclimated participants who were exposed to hot-dry (Ta = 45°C, RH = 30%), and hot-humid (Ta = 39°C, RH = 60%) at WBGT = 34° C. The result of this study demonstrated that there was no considerable difference between the changes in hot-humid and hot-dry climate conditions, except a greater decrease in performance at hot-humid conditions (51). Thermal stress also impaired workers performance in an automobile factory with a higher score for both reaction time and test duration in the case group control (WBGT = 32.6℃) compared to the control group (WBGT = 16.7℃) (18, 52). The impact of thermal stress on task performance of military operations in tropical environments was a significant challenge. Errors in a working memory and information processing increased at 35°C (25). Two studies examined the impact of heat stress on skill performance among athletes (hockey players and football players) (40, 41). Hot and moderate climate conditions following 30 and 60 min decreased intermittent high-intensity shuttle running in field hockey skill performance at 30°C (40), while mild-moderate dehydration in football players exposed to thermal stress had no effect on cognitive function at 34°C (41). Following 3 h of exposure to three different environmental conditions ( 0°C, 23°C and 40°C), cognitive performance tests (Vigilance and DG test) were impaired at 40°C compared to performance at 0°C and 23°C. Increasing physiological parameters (core body temperature and skin temperature) also indicated a high level of ambient temperature at 40°C (39). In firefighters’ tasks, neurocognitive test scores were not affected immediately after exercise at 35°C. Recall reaction time increased and a memory test reduced by 120 min after exercise by thermal protective clothing (TPC) (24).

This systematic literature review study aimed to investigate the impact of climate change on cognitive performance in workers population in different occupations such as electric arc melting, welding, power industry, etc. Most studies have been done in laboratory environments, in which several participants were examined regarding cognitive performance under a climate condition for a certain period and task (32, 35, 37). The results reported a harmful effect of thermal stress on perceptual performance, but thermal stress was unaffected or improved cognitive performance (42). Therefore, finding factors affecting cognitive performance should be considered (23). The complexity of tasks is one of the most important known factors in the cognitive workload of workers (9). In general, thermal stress can affect simple functions such as reaction time and mental transfers, while more complex functions such as vigilance, tracking and performing multiple tasks at the same time are more affected by heat stress (36). A person's skill is another factor that plays a significant role in the interaction of thermal stress and cognitive performance (38). Hancock argued that operators who are more skilled in their tasks have a greater ability to withstand the effects of thermal stress, which is related to the development of autonomous processes in the performance of the task (43). The duration of exposure has a significant impact on the relationship between thermal stress and cognitive performance (41, 47, 51). In general, it is expected that long-term exposure to a hot environment and stressful climate conditions will reduce cognitive performance; however, short-term exposure (up to 18 min) will improve performance (53). The level of heat acclimation is another main factor that has attracted researchers’ attention although the beneficial effects of acclimation are still somewhat unknown to them (33). The relationship between gender and cognitive performance under climate change should be considered in future studies (5). Wyon et al. stated that when short-term memory is required, women have a higher tolerance threshold in exposure to heat stress compared to men workers (54). The result of a study showed that having the motivation and having task-related expertise along with manager's encouragement can promote people's performance in thermal stress climate conditions (55). Vasmatzidis et al. showed that no performance decrement was observed in individuals with knowledge of specialized findings in a complex task in a hot environment ( WBGT = 34°C) (42). The impact of climate change on cognitive performance among workers population appears to be influenced by the degree of climate conditions, length of exposure, and the complexity of the task or the type of the task to be performed in different workplaces (6, 17, 56). Physiological parameter (core body temperature) is a key factor in predicting cognitive performance under climate change and thermal stress (1). Vigilance performance remains unaffected when thermal stress is not high enough to change core body temperature (57). When thermal stress is combined with physical activity, and physiological parameters markedly increase, there is a decrease in cognitive performance with different tasks (2). Considering thermal stress and implementing intervention to control the thermal situation may help to decrease the cognitive load caused by climate change on performance among workers exposed to different climate conditions (32). Increased perceptual responses and thermal discomfort are associated with performance under the thermal stress decreasing cognitive task performance when complex tasks are needed (53). In a hot environment, simple tasks (e.g., choice reaction time) did not significantly reduce, and more complex cognitive tasks were significantly impaired (58). The impairment is depended on climate conditions, type of tasks and duration of exposure (59, 60). Also, in climate conditions where thermal stress does not affect performance, the increased cognitive workload over prolonged periods imposed by the thermal stress must be considered (42). Most of the studies conducted by researchers have shown a significant positive relationship between the effect of thermal stress on cognitive performance (23, 27, 31, 41). Therefore, it can be considered that increasing people's exposure to thermal stress causes a decline in cognitive performance, especially in tasks that have some degree of cognitive load (61). Most studies were conducted in climate conditions where people were performing simple and complex cognitive tasks in exposure to thermal stress, and these complexities can cause a decrease in people's cognitive performance (62). Therefore, the knowledge about the effect of thermal stress on cognitive functions is still incomplete. Several factors such as age, gender, experience, motivation, and education can have important effects on cognitive performance that should be considered in future studies (60, 63–65). In both real-world environmental and experimental climate conditions, individual studies with human subjects should report all primary physical factors affecting thermal sensation (such as ambient temperature, personal protective equipment (PPE), RH, air velocity, infrared radiation (IR), metabolic rate, etc.), physiological parameters (heart rate, core body temperature, skin temperature, etc.), and common sources of heterogeneity (heat acclimation, rewards, learning effects, etc.), which can limit the generalizability of models and results. This study suggests that threshold limit value for thermal stress and climate change ought to take into account the specific skills required in a given workplace station, as well as the tolerance limits in perceptual and physiological responses that can be regarded as harmless, and could be used as a correct procedure and safety guideline in warm environments.

Limitations

Limited studies have been conducted on women workers in real-world environments. The limitation of a systematic approach in these studies, as well as a large number of thermal stress variables, individual and laboratory parameters, have caused researchers to not be able to report the effect of climate change on cognitive performance. Many studies have not reported standard deviations, probability values, effect sizes, real values or performance scores of cognitive and perceptual tasks. In addition, the cognitive tasks performed were significantly different from each other, as well as the weather conditions induced and the intensity of each of the stressors. These methodological changes have made it difficult to compare studies. Despite the large number of confounding factors affecting the effect of thermal stress on cognitive performance, systematic studies are limited.

Climate change is the unique challenge that affects different occupations, especially in hot seasons and countries near the equator. Knowing the effect of heat stress on cognitive and perceptual performance is important, since it help policy-makers to predict performance declining and anticipate their impact and identify potential mitigation strategies. The severity and duration of exposure to thermal stress will affect the degree of performance impairment. A difficult task is the most susceptible to heat stress. Simpler tasks are also affected, but when the temperature is extreme and thermoregulation is challenged by increased thermal stress exposure. Mitigation policies, such as acclimatization, ensuring skill in performing the job, and decreasing physiological and psychological responses, can decrease the cognitive load imposed by heat stress. More future studies are required to consider the applicability and efficacy of interventions that can improve resilience to stressors and their potential adverse effects.

Ethics approval and consent to participate

Not applicable

Consent for publication

Not applicable

Availability of data and materials

The datasets used and analyzed during the current study are available from the corresponding author on request.

Competing interests

The authors declare no competing interests.

Funding

None

Authors' contributions

AH and PH were participated in the study design, data collection, data analysis. JR, GM,AB, SFA were participated manuscript writing, revising and editing. Study was done under the supervision of AH and PH. All authors read, revised and approved the final manuscript.

Acknowledgements

Not applicable

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No competing interests reported.

The Impact of Climate Change on Cognitive Performance among Workers: A Systematic Literature Review

Status:

Version 1

Abstract

Figures

Introduction

Methods and Materials

Search

Inclusion criteria

Screening, selection, and data extraction

Quality appraisal

Results

Search results

Descriptive analysis

Thematic content analysis

The impact of climate change on the work performance

Discussion

Limitations

Conclusion

Declarations

References

Additional Declarations

Status:

Version 1