The impact of indoor air temperature on the executive functions of human brain and the physiological responses of body

Identifying physiological indicators of the cognitive, thermal, and combined (cognitive-thermal) stress conditions

Physiologically based stress detection systems have proven to be effective in identifying different stress conditions in the body to determine the source of stress and be able to counteract it. However, some stress conditions have not been widely studied, including thermal stress, cognitive stress, and combined (thermal-cognitive) stress conditions, which are frequently encountered in work or school environments. In order to develop systems to detect and differentiate these conditions, it is necessary to identify the physiological indicators that characterize each of them. The present research aims to identify which physiological indicators (heart rate, respiratory rate, galvanic skin response, and local temperature) could differentiate different stress conditions (no-stress, cognitive stress, thermal stress, and combined (thermal-cognitive) stress conditions). Thirty participants were exposed to cognitive, thermal, and combined stress sources while recording their physiological signals. The findings indicate that both mean heart rate and mean galvanic skin response identify moderate thermal and cognitive stress conditions as distinct from a no-stress condition, yet they do not differentiate between the two stress conditions. Additionally, heart rate uniquely identifies the cognitive-thermal stress condition, effectively distinguishing this combined stress condition from the singular stress conditions and the no-stress condition. Mean local temperature specifically signals thermal stress conditions, whereas mean respiratory rate accurately identifies cognitive stress conditions, with both indicators effectively separating these conditions from each other and from the no-stress condition. This is the first basis for differentiating thermal and cognitive stress conditions through physiological indicators.

Effect of extreme high temperature on cognitive function at different time scales: A national difference-in-differences analysis

BACKGROUND

Mounting evidence has demonstrated that high temperature was associated with adverse health outcomes, especially morbidity and mortality. Nonetheless, the impact of extreme high temperature on cognitive performance, which is the fundamental capacity for interpreting one's surroundings, decision-making, and acquiring new abilities, has not been thoroughly investigated.

METHODS

We aimed to assess associations between extreme high temperature at different time scales and poor cognitive function. We used longitudinal survey data from the three waves of data from China Family Panel Study, providing an 8-year follow-up of 53,008 participants from China. We assessed temperature and extreme high temperature exposure for each participant based on the residential area and date of cognitive test. We defined the proportion of days/hours above 32 °C as the metric of the exposure to extreme high temperature. Then we used generalized additive model and difference-in-differences approach to explore the associations between extreme high temperature and cognitive function.

RESULTS

Our results demonstrated that either acute exposure or long-term exposure to extreme high temperature was associated with cognitive decline. At hourly level, 0-1 hour acute exposure to extreme high temperature would induce -0.93 % (95 % CI: -1.46 %, -0.39 %) cognitive change. At annual level, 10 percentage point increase in the hours proportion exceeding 32 °C in the past two years induced -9.87 % (95 % CI: -13.99 %, -5.75 %) cognitive change. Furthermore, subgroup analyses indicated adaptation effect: for the same 10 percentage increase in hours proportion exceeding 32 °C, people in warmer areas had cognitive change of -6.41 % (-11.22 %, -1.61 %), compared with -15.30 % (-21.07 %, -9.53 %) for people in cool areas.

CONCLUSION

Our results demonstrated that extreme high temperature was associated with reduced cognitive function at hourly, daily and annual levels, warning that people should take better measures to protect the cognitive function in the context of climate change.

Effects of wearing medical gowns at different temperatures on the physiological responses of female healthcare workers during the COVID-19 pandemic

BACKGROUND

Using medical gowns with high protection against COVID-19 among healthcare workers (HCWs) may limit heat exchange, resulting in physiological challenges.

OBJECTIVE

This study aimed to compare the physiological and neurophysiological responses of female HCWs when using two typical medical gowns at different temperatures during the COVID-19 pandemic.

METHODS

Twenty healthy female HCWs participated in this study. Participants wore two types of medical gowns: Spunbond gown (SG) and laminate gown (LG). They walked on a treadmill in a controlled climate chamber for 30 minutes at three different temperatures (24, 28, and 32°C). Heart rate (HR), skin surface temperature (ST), clothing surface temperature (CT), ear temperature (ET), blood oxygen percentage (SaO2), galvanic skin response (GSR), and blood pressure were measured before and after walking on a treadmill. The study's results were analyzed using SPSS26.

RESULTS

The study found that LG led to an average increase of 0.575°C in CT compared to SG at the same temperatures (P < 0.03). The average HR increased by 6.5 bpm in LG at 28°C compared to SG at a comfortable temperature (P = 0.01). The average ET in SG and GSR in LG at 32°C increased by 0.39°C and 0.25μS, respectively, compared to the comfortable temperature (P < 0.02).

CONCLUSION

The study recommends maintaining a comfortable temperature range in hospitals to prevent physiological challenges among HCWs wearing medical gowns with high protection against COVID-19. This is important because using LG, compared to SG, at high temperatures can increase HR, ET, CT, and GSR.

Evaluation of driver drowsiness based on respiratory metrics

BACKGROUND

The transition from alertness to drowsiness can cause considerable changes in the respiratory system, providing an opportunity to detect driver drowsiness.

OBJECTIVE

The aim of this study was to determine which respiratory features indicate driver drowsiness and then use these features to classify the level of drowsiness and alertness.

METHODS

Twenty male students (mean age 25.6±2.41 years) participated in the study using a driving simulator, and eight features, including expiration duration (ED), inspiration duration (ID), peak-to-peak amplitude (PA), inspiration-to-expiration time ratio (I/E ratio), driving, timing, respiration rate (RR), and yawning, were extracted from the respiratory signal generated by abdominal motions using a belt equipped with a force sensor.

RESULTS

All eight features were statistically significant at the significance level of 0.05. Drowsiness can be detected using respiratory features with 88% accuracy, 82% precision, 86% recall, and an 90% F1 score.

CONCLUSION

The findings of this study may be useful in the development of driver drowsiness monitoring systems based on less intrusive respiratory signal analysis, particularly for specific process automation applications when vehicle control is not in the hands of the driver.

Patterns in negative emotions, sleep disorders, and temperature: Evidence from microblog big data

Existing studies have shown that temperature is related to mental illness and sleep disorders. However, few studies have explored the relationship between temperature and microblog negative emotions (MNE) and the predictive effect of MNE on sleep disorders. The present study elucidating the temperature patterns of MNE and sleep disorders, examines the predictive capability of these adverse emotions in precipitating sleep disorders, and operating within the schema of "climate-psychology-behavior". A negative binomial regression model (NBR) was formulated, amalgamating Temperature data, negative affective information procured from microblog, and sleep disorder records. Temperature and Apparent Air Temperature (AAT) were found to have a non-linear association with microblog negative emotions and sleep disorders, exhibiting a modest effect within a specified range, while extreme temperatures (both high and low) demonstrated substantial effects. In the constructed model, gender serves as a moderating factor, with females being more susceptible to temperature and AAT effects on MNE and sleep disorders than their male counterparts. Interestingly, AAT surfaced as a superior predictor compared to actual temperature. MNE were effective predictors of sleep disorders. Employing social media-centric models, as showcased in this study, augments the identification and prevention strategies targeting disease symptoms or pathologies within mental and public health domains.

Physiological comfort evaluation under different airflow directions in a heating environment

Background

Indoor airflow and thermal comfort are difficult to assess through subjective evaluations because airflow sensations can differ based on various factors, such as personal characteristics, interests, preferences, and the current state of mind. Thus, subjective evaluations should be combined with objective assessments, such as physiological measurements. This study evaluated airflow and thermal comfort through physiological measurements, including skin temperature, electroencephalography, respiration, and electrocardiography, in addition to subjective evaluations.

Methods

Twenty participants entered a test room at 30 °C after staying in an acclimation room at 18 °C for 20 min. They were exposed to indirect and direct airflow toward their faces and performed four tasks under each condition: resting, counting to 10 s following time alerts, counting to 10 s in the mind, and mental calculation. The mean speed of the air directed to the participants’ faces was 0.123 m/s and 0.225 m/s in the indirect and direct conditions, respectively.

Results

The gamma and beta bands of electroencephalograms taken at the left-temporal (T3) and left-parietal (P7) sites showed significantly lower amplitudes under the indirect condition (gamma, T3: p = 0.034, P7: p = 0.030; beta, T3: p = 0.051, P7: p = 0.028). Similarly, the variability of respiration was lower under the indirect condition (p < 0.010). The amplitudes of gamma and beta waves showed significant correlations with anxiousness levels (gamma, T3: r = 0.41; beta, T3: r = 0.35).

Conclusions

Our results suggest that indirect heating airflow causes lower mental stress and fatigue than those induced by direct flow, which is equivalent to more comfort. The results of this study suggest that physiological measurements can be used for the evaluation of unconscious indoor comfort, which cannot be detected by subjective evaluations alone.

Assessing the indoor air quality and their predictor variable in 21 home offices during the Covid-19 pandemic in Norway

In this study, concentrations of pollutants: formaldehyde, carbon dioxide (CO₂), and total volatile organic compounds (TVOC) and parameters: indoor room temperature and relative humidity (RH) were measured in 21 home offices for at least one week in winter in Trondheim, Norway. Eleven of these were measured again for the same duration in summer. Potentially explanatory variables of these parameters were collected, including building and renovation year, house type, building location, trickle vent status, occupancy, wood stove, floor material, pets, RH, and air temperature. The association between indoor air pollutants and their potential predictor variables was analyzed using generalized estimation equations to determine the significant parameters to control pollutants. Significantly seasonal differences in concentrations were observed for CO₂ and formaldehyde, while no significant seasonal difference was observed for TVOC. For TVOC and formaldehyde, trickle vent, RH, and air temperature were among the most important predictor variables. Although higher concentrations of CO₂ were measured in cases where the trickle vent was closed, the most important predictor variables for CO₂ were season, RH, and indoor air temperature. The formaldehyde concentrations were higher outside working hours but mostly below health thresholds recommendations; for CO₂, 11 of the measured cases had indoor concentrations exceeding 1000 ppm in 10% of the measured time. For TVOC, the concentrations were above the recommended values by WHO in 73% of the cases. RH was generally low in winter. The temperature was generally kept over the recommended level of 22-24 °C during working hours.

Feasibility of High-Frequency Monitoring of the Home Environment and Health in Older Adults: Proof of Concept

Technology provides new opportunities to understand and optimize the relationship between the home indoor environmental quality and health outcomes in older adults. We aimed to establish proof-of-concept and feasibility of remote, real-time, high-frequency, and simultaneous monitoring of select environmental variables and outcomes related to health and wellbeing in older adults. Thirty-four participants (27 were female) with an average age (SD) of 81 years (±7.1) were recruited from community and supportive housing environments. Environmental sensors were installed in each home and participants were asked to use a wearable device on their finger and answer smartphone-based questionnaires on a daily basis. Further, a subgroup of participants were asked to complete tablet-based cognitive tests on a daily basis. Average compliance with the wearable (time worn properly / total time with device) was 81%. Participants responded to 69% of daily smartphone surveys and completed 80% of the prescribed cognitive tests. These results suggest that it is feasible to study the impact of the home thermal environment and air quality on biological rhythms, cognition, and other outcomes in older adults. However, the success of non-passive data collection elements may be contingent upon baseline cognition.

Analysis of the spatiotemporal mechanism of high temperature on residents’ irritability in Beijing based on multiscale geographically weighted regression model

The emotional health of urban residents is increasingly threatened by high temperatures due to global heating. However, how high temperature affects residents’ emotional health remains unknown. Therefore, this study investigated the spatiotemporal pattern of temperature’s impact on residents’ irritability using data from summer high-temperature measurement and emotional health survey in Beijing, combined with remote sensing images and statistical yearbooks. In detail, this study formulated a multiscale geographically weighted regression (MGWR) model, to study the differentiated and spatial influence of high-temperature factors on emotion. Results show: From 09:00 to 20:00, irritability level rose first then gradually dropped, with a pattern of “aggregation-fragmentation-aggregation.” Irritability is very sensitive to intercept and building density (BD). Other variables all have spatial heterogeneity [except for fraction vegetation coverage (FVC) or road network density (RND) as they are global variables], including normalized difference vegetation index (NDVI), water surface rate (WSR), floor area ratio (FAR), and Modified Normalized Difference Water Index (MNDWI) (sorted from the smallest to the largest in scale). Irritability is negatively correlated with NDVI, WSR, and RND, while positively correlated with intercept, MNDWI, FVC, FAR, and BD. Influence on irritability: WSR &lt; NDVI &lt; BD &lt; MNDWI &lt; RND &lt; intercept &lt; FVC &lt; FAR.

Indoor Air Quality Monitoring and Characterization of Airborne Workstations Pollutants within Detergent Production Plant

The indoor air quality (IAQ) of five workstations within a detergent production unit was monitored. Particulate matter (PM) was measured using a gravitational settlement method, and later characterized. To ascertain the quality of indoor air within the workstations, which could directly or indirectly affect the health and performance of the workers, a physical inspection of the plant premises was undertaken. The mean value of the following air-quality parameters; particulate matter(PM_2.5), particulate matter (PM₁₀), formaldehyde (HCHO), volatile organic compounds (VOCs), carbon dioxide (CO₂), temperature (T) and percent relative humidity (%RH) were obtained within the range of 24.5-48.5 µg/m³, 26.75-61.75 µg/m³, 0.0-0.012 mg/m³, 0.09-1.35 mg/m³, 1137-1265 ppm, 25.65-28.15 °C and 20.13-23.8%, respectively. Of the particulate matter components characterized, sodium oxide (Na₂O)-25.30 mg/m³, aluminum oxide (Al₂O₃)-22.93 mg/m³, silicon dioxide (SiO₂)-34.17 mg/m³, sulfur trioxide (SO₃)-41.57 mg/m³, calcium oxide (CaO)-10.94 mg/m³ and iron III oxide (Fe₂O₃)-19.23 mg/m³, were of significance. These results, compared with international standards for industrial indoor air quality, suggest that indoor air contamination emanating from the chemicals used in production workstations is traced to the design of the plant structures and the activities carried out within the workstations.

Analysis of the impact of urban summer high temperatures and outdoor activity duration on residents' emotional health: Taking hostility as an example

The combined effect of global warming and the heat island effect keeps the temperature of cities rising in the summer, seriously threatening the physical and mental health of urban residents. Taking the area within the Sixth Ring Road of Beijing as an example, based on Landsat remote sensing images, meteorological stations, and questionnaires, this study established a relational model between temperature and hostility and then analyzed the changes in the emotional health risk (hostility) in the study area and the mechanism of how outdoor activity duration influences hostility. Results show that: (1) the area within the Sixth Ring Road of Beijing had a higher and higher temperature from 1991 to 2020. Low-temperature areas gradually shrank, and medium- and high-temperature areas extended outwards from the center. (2) The threat of high temperature to residents' hostility gradually intensified—the sphere of influence expanded, low-risk areas quickly turned into medium-high-risk areas, and the level of hostility risk increased. Level 1 risk areas of hostility had the most obvious reduction—a 74.33% reduction in area proportion; meanwhile, Level 3 risk areas had the most significant growth—a 50.41% increase in area proportion. (3) In the first 120 min of outdoor activities under high temperature, residents' hostility was negatively correlated with outdoor activity duration; after more than 120 min, hostility became positively correlated with duration. Therefore, figuring out how temperature changes influence human emotions is of great significance to improving the living environment and health level of residents. This study attempts to (1) explore the impact of temperature changes and outdoor activity duration on hostility, (2) evaluate residents' emotional health risk levels affected by high temperature, and (3) provide a theoretical basis for the early warning mechanism of emotional health risk and the planning of healthy cities.

Effects of a cool classroom microclimate on cardiac autonomic control and cognitive performances in undergraduate students

An inverted U-shape relationship between cognitive performance and indoor temperature with best performance peaking at 21.6 °C was previously described. Little is known on classroom temperature reduction effects on cognitive performances and cardiac autonomic profile, during the cold season. Fifteen students underwent electrocardiogram recording during a lecture in two days in December when classroom temperatures were set as neutral (NEUTRAL, 20-22 °C) and cool (COOL, 16-18 °C). Cognitive performance (memory, verbal ability, reasoning, overall cognitive C-score) was assessed by Cambridge Brain Science cognitive evaluation tool. Cardiac autonomic control was evaluated via the analysis of spontaneous fluctuations of heart period, as the temporal distance between two successive R-wave peaks (RR). Spectral analysis provided the power in the high frequency (HF, 0.15-0.40 Hz) and low frequency (LF, 0.04-0.15 Hz) bands of RR variability. Sympatho-vagal interaction was assessed by LF to HF ratio (LF/HF). Symbolic analysis provided the fraction of RR patterns composed by three heart periods with no variation (0 V%) and two variations (2 V%), taken as markers of cardiac sympathetic and vagal modulations, respectively. The students' thermal comfort was assessed during NEUTRAL and COOL trials. Classroom temperatures were 21.5 ± 0.8 °C and 18.4 ± 0.4 °C during NEUTRAL and COOL. Memory, verbal ability, C-Score were greater during COOL (13.01 ± 3.43, 12.32 ± 2.58, 14.29 ± 2.90) compared to NEUTRAL (9.98 ± 2.26, p = 0.002; 8.57 ± 1.07, p = 0.001 and 10.35 ± 3.20, p = 0.001). LF/HF (2.4 ± 1.7) and 0 V% (23.2 ± 11.1%) were lower during COOL compared to NEUTRAL (3.7 ± 2.8, p = 0.042; 28.1 ± 12.2.1%, p = 0.031). During COOL, 2 V% was greater (30.5 ± 10.9%) compared to NEUTRAL (26.2 ± 11.3, p = 0.047). The students' thermal comfort was slightly reduced during COOL compared to NEUTRAL trial. During cold season, a better cognitive performance was obtained in a cooler indoor setting enabling therefore energy saving too.

The Role of Temperature in Moral Decision-Making: Limited Reproducibility

Temperature is one of the major environmental factors that people are exposed to on a daily basis, often in conditions that do not afford control. It is known that heat and cold can influence a person’s productivity and performance in simple tasks. With respect to social cognition, it has also been suggested that temperature impacts on relatively high-level forms of decision-making. For instance, previous research demonstrated that cold temperature promotes utilitarian judgment in a moral dilemma task. This effect could be due to psychological processing, when a cool temperature primes a set of internal representations (associated with “coldness”). Alternatively, the promotion of utilitarian judgment in cold conditions could be due to physiological interference from temperature, impeding on social cognition. Refuting both explanations of psychological or physiological processing, however, it has been suggested that there may be problems of reproducibility in the literature on temperature modulating complex or abstract information processing. To examine the role of temperature in moral decision-making, we conducted a series of experiments using ambient and haptic temperature with careful manipulation checks and modified task methodology. Experiment 1 manipulated room temperature with cool (21°C), control (24°C) and hot (27°C) conditions and found only a cool temperature effect, promoting utilitarian judgment as in the previous study. Experiment 2 manipulated the intensity of haptic temperature but failed to obtain the cool temperature effect. Experiments 3 and 4 examined the generalizability of the cool ambient temperature effect with another moral judgment task and with manipulation of exposure duration. However, again there were no cool temperature effects, suggesting a lack of reproducibility. Despite successful manipulations of temperature in all four experiments, as measured in body temperature and the participants’ self-reported perception, we found no systematic influence of temperature on moral decision-making. A Bayesian meta-analysis of the four experiments showed that the overall data tended to provide strong support in favor of the null hypothesis. We propose that, at least in the range of temperatures from 21 to 27°C, the cool temperature effect in moral decision-making is not a robust phenomenon.

Sensory perception of environmental cues as a modulator of aging and neurodegeneration: Insights from Caenorhabditis elegans

Environmental stimuli such as temperature, food, and smell significantly influence the physiology and behavior of animals. Animals are differentially adapted to maintain their internal body functions in response to varied environmental conditions. These external cues are sensed by specialized neurons which are a part of the chemosensory and thermosensory systems. The inability to respond correctly to varied environmental conditions may result in compromised bodily functions and reduced longevity. For example, the ability to sense food is derived from the integrated action of olfactory and gustatory systems. The damage to the olfactory system will affect our decision of palatable food items which in turn can affect the response of the gustatory system, ultimately causing abnormal feeding habits. Recent studies have provided evidence that aging is regulated by sensory perception of environment. Aging is one of the most common causes of various neurodegenerative diseases and the perception of environmental cues is also found to regulate the development of neurodegenerative phenotype in several animal models. However, specific molecular signaling pathways involved in the process are not completely understood. The research conducted on one of the best-studied animal models of aging, Caenorhabditis elegans, has demonstrated multiple examples of gene-environment interaction at the neuronal level which affects life span. The findings may be useful to identify the key neuronal regulators of aging and age-related diseases in humans owing to conserved core metabolic and aging pathways from worms to humans.

Human cognitive functions and psycho-physiological responses under low thermal conditions in a simulated office environment

BACKGROUND

In office environments, thermal comfort is one of the most significant factor affecting employees' performance.

OBJECTIVE

This study aimed to determine the effects of exposure to low air temperatures on human cognitive performance, physiological responses, and thermal perceptions during mental work.

METHODS

Twenty-four volunteers with an age range of 18-30 years participated in this study. The subjects were exposed to four different air temperatures (10, 14, 18, and 22°C) in a climate chamber based on a within-subject design. The n-back, CPT, and PVT tests were employed to evaluate some basic aspects of cognitive performance. Body physiological responses and the subjective thermal comfort were also measured.

RESULTS

When the thermal condition deviated from relatively neutral temperature, the subjects' cognitive responses significantly disturbed (P < 0.05), such that the response accuracy was more affected by reduction of air temperature. The blood pressures and heart rate, galvanic skin response, and respiration rate increased as the air temperature decreased (P < 0.05), such that the galvanic skin response as a stress indicator was more affected. In the test configurations, as a result of decrease in air temperature of 1°C, the finger and body skin temperatures reduced to 0.74°C and 0.25°C, respectively.

CONCLUSIONS

The findings confirmed that low thermal condition can considerably affect cognitive performance and physiological responses during some office work tasks. The subjects' thermal comfort votes proposed that air temperature lower than 14 °C can be intolerable for employees during routine mental work. It is suggested that personalized conditioning systems should be used to provide individual thermal comfort in moderate cold air conditions.

Health, work performance, and risk of infection in office-like environments: The role of indoor temperature, air humidity, and ventilation

Epidemiological and experimental studies have revealed the effects of the room temperature, indoor air humidity, and ventilation on human health, work and cognitive performance, and risk of infection. In this overview, we integrate the influence of these important microclimatic parameters and assess their influence in offices based on literature searches. The dose-effect curves of the temperature describe a concave shape. Low temperature increases the risk of cardiovascular and respiratory diseases and elevated temperature increases the risk of acute non-specific symptoms, e.g., dry eyes, and respiratory symptoms. Cognitive and work performance is optimal between 22 °C and 24 °C for regions with temperate or cold climate, but both higher and lower temperatures may deteriorate the performances and learning efficiency. Low temperature may favor virus viability, however, depending on the status of the physiological tissue in the airways. Low indoor air humidity causes vulnerable eyes and airways from desiccation and less efficient mucociliary clearance. This causes elevation of the most common mucous membrane-related symptoms, like dry and tired eyes, which deteriorates the work performance. Epidemiological, experimental, and clinical studies support that intervention of dry indoor air conditions by humidification alleviates symptoms of dry eyes and airways, fatigue symptoms, less complaints about perceived dry air, and less compromised work performance. Intervention of dry air conditions by elevation of the indoor air humidity may be a non-pharmaceutical treatment of the risk of infection by reduced viability and transport of influenza virus. Relative humidity between 40 and 60% appears optimal for health, work performance, and lower risk of infection. Ventilation can reduce both acute and chronic health outcomes and improve work performance, because the exposure is reduced by the dilution of the indoor air pollutants (including pathogens, e.g., as virus droplets), and in addition to general emission source control strategies. Personal control of ventilation appears an important factor that influences the satisfaction of the thermal comfort due to its physical and positive psychological impact. However, natural ventilation or mechanical ventilation can become sources of air pollutants, allergens, and pathogens of outdoor or indoor origin and cause an increase in exposure. The "health-based ventilation rate" in a building should meet WHO's air quality guidelines and dilute human bio-effluent emissions to reach an acceptable perceived indoor air quality. Ventilation is a modifying factor that should be integrated with both the indoor air humidity and the room temperature in a strategic joint control to satisfy the perceived indoor air quality, health, working performance, and minimize the risk of infection.

Perceived air quality and cognitive performance decrease at moderately raised indoor temperatures even when clothed for comfort

This study investigated whether adjusting clothing to remain in neutral thermal comfort at moderately elevated temperature is capable of avoiding negative effects on perceived acute subclinical health symptoms, comfort, and cognitive performance. Two temperatures were examined: 23°C and 27°C. Twelve subjects were able to remain thermally comfortable at both temperatures by adjusting their clothing. They rated the physical environment, their comfort, the intensity of acute subclinical health symptoms, and their mental load, and they performed a number of cognitive tasks. Their physiological reactions were monitored. Their performance of several tasks was significantly worse at 27°C, and they reported increased mental load at this temperature. Skin temperature and humidity and respiration rate were higher, while blood oxygen saturation (SpO2) and pNN50 were lower at this temperature, the latter indicating increased stress. It is inferred that the observed physiological responses were mainly responsible for the negative effects on performance, as the subjects did not indicate any increased intensity of acute subclinical health symptoms although perceived air quality was worse at the higher temperature. The present results suggest that moderately elevated temperatures should be avoided even if thermal comfort can be achieved, as it may lead to reduced performance.

The Effects of Noise on Human Cognitive Performance and Thermal Perception under Different Air Temperatures

BACKGROUND

Environmental factors are interrelated, and human comfort is a complex state that is under the influence of all these factors perceived by a person. We aimed to investigate the effects of noise on human cognitive performance and thermal perception under different air temperatures.

STUDY DESIGN

An experimental study.

METHODS

This study was conducted on 24 volunteers (12 males and 12 females) aged 18-30 yr old. All the experiments were carried out in a climate chamber located in Hamadan University of Medical Sciences in 2018. The subjects were exposed to ten different conditions set by a combination of three different air temperatures (14, 18, and 22 °C), three different noise levels (55, 65 and 75 dBA), and one irrelevant speech level in the climate chamber. The n-back, CPT, and PVT tests were employed to evaluate different aspects of cognitive performance. Thermal comfort and thermal sensation were measured with subjective questionnaires.

RESULTS

With increasing noise under different air temperatures, working memory (P=0.001), sustained attention (P=0.001), and simple reaction time (P=0.001) were significantly disturbed. The combined effects of noise and low air temperature on working memory, sustained attention, and reaction time were higher than the effect of each of them individually. As compared with air temperature, noise has a larger effect on working memory, sustained attention, and reaction time in the test configurations.

CONCLUSION

The cognitive performance effects from noise has one veto power over these effects from low air temperature. Speech sound had more negative effects on subjects' cognitive functions than the typical noise caused by office equipment. The subjective thermal perceptions were also influenced by noise at lower air temperatures.