The sleep architecture of Australian volunteer firefighters during a multi-day simulated wildfire suppression: Impact of sleep restriction and temperature

Occupation-Induced Fatigue and Impacts on Emergency First Responders: A Systematic Review

Fatigue in emergency first responders (EFRs) is known to affect performance abilities and safety outcomes for both patients and EFRs. The primary aim of this review was to determine the main contributors to occupation-induced fatigue in EFRs and its subsequent impacts. Following the PRIMSA checklist, academic databases (Medline, Embase, CINAHL, and SPORTDiscus) were searched using key terms with results subjected to inclusion and exclusion criteria. Populations of interest were firefighters, paramedics, or emergency call centre personnel. Of the 5633 records identified, 43 studies, which reported on 186 unique measures from a total population of 6373 participants, informed the review. Synthesis revealed fatigue was caused by lack of sleep during the shift and consistent poor sleep quality which negatively impacted cognitive function, alertness, and physical and mental health while increasing safety-compromising behaviours and injuries. Both subjective and objective assessments of fatigue are necessary for effective risk management in EFRs. EFRs that are consistently fatigued are at a greater risk of poor physical and mental health, reduced cognitive function, and increased injuries. No studies reported on fatigue in emergency call centre personnel, highlighting a literature gap. Funding was provided by the Australian Capital Territory Emergency Services Agency. Preregistration was filed in OSF: osf.io/26f3s.

Sleep Architecture and Sleep EEG Alterations are Associated with Impaired Cognition Under Sleep Restriction

Purpose

Many studies have investigated the cognitive, emotional, and other impairments caused by sleep restriction. However, few studies have explored the relationship between cognitive performance and changes in sleep structure and electroencephalography (EEG) during sleep. The present study aimed to examine whether changes in sleep structure and EEG can account for cognitive impairment caused by sleep restriction.

Patients and Methods

Sixteen young adults spent five consecutive nights (adaptation 9h, baseline 8h, 1st restriction 6h, 2nd restriction 6h, and recovery 10h) in a sleep laboratory, with polysomnography recordings taken during sleep. Throughout waking periods in each condition, participants completed the psychomotor vigilance test (PVT), which measures vigilant attention, and the Go/No-Go task, which measures inhibition control.

Results

The results showed that sleep restriction significantly decreased the proportion of N1 and N2 sleep, increased the proportion of N3 sleep, and reduced the time spent awake after sleep onset (WASO) and sleep onset latency. Poorer performance on the PVT and Go/No Go task was associated with longer WASO, a larger proportion of N3 sleep, and a smaller proportion of N2 sleep. Additionally, the power spectral density of delta waves significantly increased after sleep restriction, and this increase predicted a decrease in vigilance and inhibition control the next day.

Conclusion

These findings suggest that sleep architecture and EEG signatures may partially explain cognitive impairment caused by sleep restriction.

Global prevalence and associated factors of sleep disorders and poor sleep quality among firefighters: A systematic review and meta-analysis

Lack of sleep can affect the health and performance of firefighters. This systematic review and meta-analysis estimated the global prevalence of sleep disorders and poor sleep quality among firefighters and reported associated factors. Four academic databases (Scopus, PubMed, Web of Science, and Embase) were systematically searched from January 1, 2000 to January 24, 2022. These databases were selected as they are known to index studies in this field. The search algorithm included two groups of keywords and all possible combinations of these words. The first group included keywords related to sleep and the second group keywords related to the firefighting profession. The relevant Joanna Briggs Institute checklist was used to evaluate study quality. Data from eligible studies were included in a meta-analysis. In total, 47 articles informed this review. The pooled prevalence of sleep disorders and poor sleep quality in firefighters were determined as 30.49% (95% CI [25.90, 35.06]) and 51.43% (95% CI [42.76, 60.10]), respectively. The results of a subgroup analysis showed that individuals in low- and middle-income countries (LMICs) had a higher prevalence of sleep disorders than those in high-income countries (HICs) but HICs had a higher prevalence of poor sleep quality than LMICs. Various factors, including shift work, mental health, injuries and pain, and body mass index were associated with sleep health. The findings of this review highlight the need for sleep health promotion programs in firefighters.

Working hours, sleep, and fatigue in the public safety sector: A scoping review of the research

BACKGROUND

The public safety sector includes law enforcement officers (LEO), corrections officers (CO), firefighter service (FF), wildland firefighting (WFF), and emergency medical services (EMS), as defined in the National Occupational Research Agenda (NORA) of the National Institute for Occupational Safety and Health (NIOSH). Across these occupations, shiftwork, long-duration shifts, and excessive overtime are common. Our objective was to identify research gaps related to working hours, sleep, and fatigue among these workers.

METHODS

We used a scoping review study design that included searches of MEDLINE, Embase, CAB Abstracts, Global Health, PsychInfo, CINAHL, Scopus, Academic Search Complete, Agricultural and Environmental Science Collection, ProQuest Central, Cochrane Library, Safety Lit, Homeland Security Digital Library, and Sociological Abstracts using a range of occupational search terms and terms related to working hours, sleep, and fatigue.

RESULTS

Out of 3415 articles returned from our database search, 202 met all inclusion criteria. Six common outcomes related to working hours, sleep, and fatigue emerged: sleep, fatigue, work performance, injury, psychosocial stress, and chronic disease. Nearly two-thirds (59%, n = 120) of the studies were observational, of which 64% (n = 77) were cross sectional and 9% were (n = 11) longitudinal; 14% (n = 30) of the studies were reviews; and 19% (n = 39) were experimental or quasi-experimental studies. Only 25 of the 202 articles described mitigation strategies or interventions. FFs, LEOs, EMS, and WFFs were the most studied, followed by COs.

CONCLUSIONS

In general, more longitudinal and experimental studies are needed to enrich the knowledge base on the consequences of long working hours, poor sleep, and fatigue in the public safety sector. Few experimental studies have tested novel approaches to fatigue mitigation in diverse sectors of public safety. This gap in research limits the decisions that may be made by employers to address fatigue as a threat to public-safety worker health and safety.

Health risks and mitigation strategies from occupational exposure to wildland fire: a scoping review

OBJECTIVES

Due to accelerating wildland fire activity, there is mounting urgency to understand, prevent, and mitigate the occupational health impacts associated with wildland fire suppression. The objectives of this review of academic and grey literature were to: 1. Identify the impact of occupational exposure to wildland fires on physical, mental, and emotional health; and 2. Examine the characteristics and effectiveness of prevention, mitigation, or management strategies studied to reduce negative health outcomes associated with occupational exposure to wildland fire.

METHODS

Following established scoping review methods, academic literature as well as government and industry reports were identified by searching seven academic databases and through a targeted grey literature search. 4679 articles were screened using pre-determined eligibility criteria. Data on study characteristics, health outcomes assessed, prevention or mitigation strategies studied, and main findings were extracted from each included document. The results of this scoping review are presented using descriptive tables and a narrative summary to organize key findings.

RESULTS

The final sample was comprised of 100 articles: 76 research articles and 24 grey literature reports. Grey literature focused on acute injuries and fatalities. Health outcomes reported in academic studies focused on respiratory health (n = 14), mental health (n = 16), and inflammation and oxidative stress (n = 12). The identified studies evaluated short-term outcomes measuring changes across a single shift or wildland fire season. Most research was conducted with wildland firefighters and excluded personnel such as aviation crews, contract crews, and incident management teams. Five articles reported direct study of mitigation strategies, focusing on the potential usage of masks, advanced hygiene protocols to reduce exposure, fluid intake to manage hydration and core temperature, and glutamine supplementation to reduce fatigue.

CONCLUSIONS

While broad in scope, the evidence base linking wildland fire exposure to any one health outcome is limited. The lack of long-term evidence on changes in health status or morbidity is a clear evidence gap and there is a need to prioritize research on the mental and physical health impact of occupational exposure to wildland fire.

Hot, Tired and Hungry: The Snacking Behaviour and Food Cravings of Firefighters During Multi-Day Simulated Wildfire Suppression

Firefighters are exposed to numerous stressors during wildfire suppression, including working in hot temperatures and sleep restricted conditions. Research has shown that when sleep restricted, individuals choose foods higher in carbohydrates, fat, and sugar, and have increased cravings for calorie dense foods. However, there is currently no research on the combined effect of heat and sleep restriction on snacking behaviour. Conducting secondary analyses from a larger study, the current study aimed to investigate the impact of heat and sleep restriction on snacking behaviour and food cravings. Sixty-six firefighters completed three days of simulated physically demanding firefighting work and were randomly allocated to either the control (n = 18, CON; 19 °C, 8 h sleep opportunity), sleep restricted (n = 16, SR; 19 °C, 4-h sleep opportunity), hot (n = 18, HOT; 33 °C, 8 h sleep opportunity), or hot and sleep restricted (n = 14 HOT + SR; 33 °C, 4-h sleep opportunity) condition. During rest periods firefighters were able to self-select sweet, savoury, or healthy snacks from a ration pack and were asked to rate their hunger, fullness, and cravings every two hours (eating block). Mixed model analyses revealed no difference in total energy intake between conditions, however there was a significant interaction between eating block and condition, with those in the CON, HOT, and HOT + SR condition consuming significantly more energy between 1230 and 1430 compared to the SR condition (p = 0.002). Sleep restriction and heat did not impact feelings of hunger and fullness across the day, and did not lead to greater cravings for snacks, with no differences between conditions. These findings suggest that under various simulated firefighting conditions, it is not the amount of food that differs but the timing of food intake, with those that are required to work in hot conditions while sleep restricted more likely to consume food between 1230 and 1430. This has potential implications for the time of day in which a greater amount of food should be available for firefighters.

Impacts of Australian Firefighters' On-Call Work Arrangements on the Sleep of Partners

On-call work arrangements are commonly utilised in the emergency services sector and are consistency associated with inadequate sleep. Despite sleep being a common shared behaviour, studies are yet to assess the impact of on-call work on the sleep of co-sleeping partners. This study aimed to investigate whether frequent 24/7 on-call work impacted the sleep and relationship happiness of firefighters' partners. Two key research questions were investigated: (1) Does the frequency of calls impact sleep and relationship happiness? and, (2) Does the (a) sleep quantity and (b) sleep quality of partners impact perceived relationship happiness? A cross-sectional study was conducted using an online questionnaire completed by partners of on-call workers (n = 66; 93% female). The questionnaire included items on (i) sleep quantity and quality, (ii) on-call sleep disturbances and, (iii) relationship happiness. Responses were analysed using logistic regression models. Higher overnight call frequency was associated with greater self-reported levels of inadequate sleep (<7 h per night; p = 0.024). Support for continuance of a firefighter's role was less likely if the partner reported they regularly had trouble falling asleep within 30 min (p < 0.001). There were no other significant relationships between the frequency of calls or other sleep quantity or quality variables and relationship happiness. This study provides important first insights into how firefighters' on-call work arrangements impact partners' sleep. Future research is needed across periods of high and low call demand, using objective measures of sleep to further define the impacts of on-call work on partners' sleep.

The impact of anticipating a stressful task on sleep inertia when on-call

Sleep inertia, the state of reduced alertness upon waking, can negatively impact on-call workers. Anticipation of a stressful task on sleep inertia, while on-call was investigated. Young, healthy males (n = 23) spent an adaptation, control and two counterbalanced on-call nights in the laboratory. When on-call, participants were told they would be woken to a high or low stress task. Participants were not woken during the night, instead were given a 2300-0700 sleep opportunity. Participants slept ∼7.5-h in all conditions. Upon waking, sleep inertia was quantified using the Karolinska Sleepiness Scale and Psychomotor Vigilance and Spatial Configuration Tasks, administered at 15-min intervals. Compared to control, participants felt sleepier post waking when on-call and sleepiest in the low stress compared to the high stress condition (p < .001). Spatial performance was faster when on-call compared to control (p < .001). Findings suggest that anticipating a high-stress task when on-call, does not impact sleep inertia severity.

Twenty-four-hour pattern of operations-related injury occurrence and severity of off-site/on-call volunteer French firefighters

We assessed the 24-h pattern of operations-related injuries (ORI) experienced by scheduled off-site/on-call French volunteer firefighters (VFF) through analysis of an archival database. Occurrence and severity - evaluated by number of lost work days (LWD) and total medical costs (TMC) - of ORI were explored in terms of risk ratios, respectively, number of ORI/number of service operations (RR_ORI), number of LWD/number of ORI (RS_LWD,) and TMC/number of ORI (RS_TMC). Additionally, the collective work performance of all involved VFF was measured in terms of the lag time (LT) between emergency call-center firefighter-answered communication for service of observer-presumed out-of-hospital cardiac arrest (OHCA) and departure of vehicle from fire station to render aid, designated LT_OHCA. Cosinor and cross-correlation statistical methods were applied. A total of 252 ORI occurred while performing 146,479 service operations. High-amplitude 24 h variation was detected in RR_ORI (p < .003), SR_LWD (p < .001), SR_TMC (p < .012), and LT_OHCA (p < .001), all with nocturnal peak time. Coherence was found between the day/night variation of LT_OHCA and RR_ORI (r = 0.7, p < .0002), SR_LWD (r = 0.5, p < .02), and SR_TMC (r = 0.4, p < .05). This investigation verifies the occurrence and severity of ORI of scheduled off-site/on-call VFF exhibit high-amplitude 24 h patterning with nocturnal excess that closely coincides with their day/night work performance measured by LT_OHCA. These findings, which are essentially identical to ones of a previous study entailing on-site/on-call career firefighters, indicate the need for fatigue management and ORI prevention programs not yet available to VFF, who compose the majority of the field service workforce of French fire departments. Abbreviations:FF: firefighters; CFF: career firefighters; VFF: volunteer firefighters; FD: fire department; LT_OHCA: lag time (LT) response in min:sec between fire department call-center-answered communication for service of presumed out-of-hospital cardiac arrest (OHCA) and departure from fire station of vehicle to render aid; LWD: lost work days; ORI: operations-related injuries; SR_LWD: severity ratio of operations-related injuries in terms of number of lost work days, calculated as number of lost work days/number of operations-related injuries; RR_ORI: risk ratio of operations-related injuries calculated as number of operations-related injuries/number of operations; SR_TMC: severity ratio of operations-related injuries in terms of total medical costs, calculated as total medical costs/number of operations-related injuries; TMC: total medical costs.

Adding sleep restriction to the equation: impact on wildland firefighters' work performance and physiology in hot conditions

PURPOSE

To examine the effects of sleep restriction on firefighters' physical task performance, physical activity, and physiological and perceived exertion during simulated hot wildfire conditions.

METHODS

31 firefighters were randomly allocated to either the hot (n = 18, HOT; 33 °C, 8-h sleep opportunity) or hot and sleep restricted (n = 13, HOT + SR; 33 °C, 4-h sleep opportunity) condition. Intermittent, self-paced work circuits of six firefighting tasks were performed for 3 days. Firefighters self-reported ratings of perceived exertion. Heart rate, core temperature, and physical activity were measured continuously. Fluids were consumed ad libitum, and all food and fluids consumed were recorded. Urine volume and urine specific gravity (USG) were analysed and sleep was assessed using polysomnography (PSG).

RESULTS

There were no differences between the HOT and HOT + SR groups in firefighters' physical task performance, heart rate, core temperature, USG, or fluid intake. Ratings of perceived exertion were higher (p < 0.05) in the HOT + SR group for two of the six firefighting tasks. The HOT group spent approximately 7 min more undertaking moderate physical activity throughout the 2-h work circuits compared to the HOT + SR group.

CONCLUSION

Two nights of sleep restriction did not influence firefighters' physical task performance or physiological responses during 3 days of simulated wildfire suppression. Further research is needed to explore firefighters' pacing strategies during real wildfire suppression.

Sleep Quantity and Quality of Ontario Wildland Firefighters Across a Low-Hazard Fire Season

OBJECTIVE

The aim of the study was to assess the sleep quality, quantity, and fatigue levels of Canadian wildland firefighters while on deployment.

METHODS

Objective and subjective sleep and fatigue measures were collected using actigraphy and questionnaires during non-fire (Base) and fire (Initial Attack and Project) deployments.

RESULTS

Suboptimal sleep quality and quantity were more frequently observed during high-intensity, Initial Attack fire deployments. Suboptimal sleep was also exhibited during non-fire (Base) work periods, which increases the risk of prefire deployment sleep debt. Self-reported, morning fatigue scores were low-to-moderate and highest for Initial Attack fire deployments.

CONCLUSIONS

The study highlights the incidence of suboptimal sleep patterns in wildland firefighters during non-fire and fire suppression work periods. These results have implications for the health and safety practices of firefighters given the link between sleep and fatigue, in a characteristically hazardous occupation.