The acute physiological stress response to an emergency alarm and mobilization during the day and at night

Blood pressure responses are dependent on call type and related to hypertension status in firefighters

BACKGROUND

Impaired cardiovascular health is a concern for firefighters, with over 50% of line-of-duty deaths having cardiac causes. Many firefighters have hypertension and <25% have their blood pressure (BP) controlled. The alarm response could be an unidentified cardiac risk, but interestingly, the BP response to different calls and on-the-job activity is unknown.

PURPOSE

We aimed to measure the physiological stress resulting from different call types (fire, medical) and job activity (riding apparatus, pre-alert alarms) through ambulatory BP (ABP) monitoring in a population of firefighters.

MATERIALS AND METHODS

During 111 12-h work shifts firefighters wore an ABP monitor. BP was measured at 30-min intervals and manual measurements were prompted when the pager went off or whenever they felt stress.

RESULTS

Firefighters were hypertensive (124.3 ± 9.9/78.1 ± 6.7 mmHg), overweight (30.2 ± 4.6 kg/m2), middle-aged (40.5 ± 12.6 years) and experienced (17.3 ± 11.7 years). We calculated an average 11% increase in systolic and 10.5% increase in diastolic BP with alarm. Systolic BP (141.9 ± 13.2 mmHg) and diastolic BP (84.9 ± 11.1 mmHg) and the BP surges were higher while firefighters were responding to medical calls compared to fire calls. Between BP groups we found that medical call systolic BP (p = .001, d = 1.2), diastolic BP (p = .017, d = 0.87), and fire call systolic BP (p = .03, d = 0.51) levels were higher in the hypertensive firefighters.

CONCLUSION

This is the first report of BP surge responses to alarms and to occupational activities in firefighters, and medical calls elicited the largest overall responses.PLAIN LANGUAGE SUMMARYCardiovascular disease and impaired cardiovascular health are substantially more prevalent in firefighters, with over 50% of line-of-duty deaths being cardiac related.Many firefighters are diagnosed with high blood pressure (hypertension), which is known to increase the risk of heart attacks, strokes, heart disease, and other serious health complications.Upon stress, our body enacts the 'fight or flight' response where sympathetic nervous system activity triggers an immediate increase in heart rate and blood pressure. This response can be dangerous when surges reach extreme levels due to underlying impaired cardiovascular function. It is known that alarm sounds trigger a stress response.Firefighters respond to different alarms while on the job, each indicating different call types, such as a house fire or a medical emergency. Due to the prevalence of impaired cardiovascular health in firefighters, the physical stress resulting from these alerts is cause for concern.The blood pressure surge response to different call types and job activities in healthy and hypertensive firefighters had not been measured before this study.Through the ambulatory blood pressure monitoring of 111 on-duty firefighters, this study discovered that medical calls caused the greatest blood pressure and heart rate surge.Also, firefighters with hypertension experienced a greater blood pressure surge in response to alarms than their non-hypertensive co-workers.

Modeling Brain Dynamics During Virtual Reality-Based Emergency Response Learning Under Stress

BACKGROUND

Stress affects learning during training, and virtual reality (VR) based training systems that manipulate stress can improve retention and retrieval performance for firefighters. Brain imaging using functional Near Infrared Spectroscopy (fNIRS) can facilitate development of VR-based adaptive training systems that can continuously assess the trainee's states of learning and cognition.

OBJECTIVE

The aim of this study was to model the neural dynamics associated with learning and retrieval under stress in a VR-based emergency response training exercise.

METHODS

Forty firefighters underwent an emergency shutdown training in VR and were randomly assigned to either a control or a stress group. The stress group experienced stressors including smoke, fire, and explosions during the familiarization and training phase. Both groups underwent a stress memory retrieval and no-stress memory retrieval condition. Participant's performance scores, fNIRS-based neural activity, and functional connectivity between the prefrontal cortex (PFC) and motor regions were obtained for the training and retrieval phases.

RESULTS

The performance scores indicate that the rate of learning was slower in the stress group compared to the control group, but both groups performed similarly during each retrieval condition. Compared to the control group, the stress group exhibited suppressed PFC activation. However, they showed stronger connectivity within the PFC regions during the training and between PFC and motor regions during the retrieval phases.

DISCUSSION

While stress impaired performance during training, adoption of stress-adaptive neural strategies (i.e., stronger brain connectivity) were associated with comparable performance between the stress and the control groups during the retrieval phase.

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.

Snoozing: an examination of a common method of waking

Study Objectives

Snoozing was defined as using multiple alarms to accomplish waking, and considered as a method of sleep inertia reduction that utilizes the stress system. Surveys measured snoozing behavior including who, when, how, and why snoozing occurs. In addition, the physiological effects of snoozing on sleep were examined via wearable sleep staging and heart rate (HR) activity, both over a long time scale, and on the days that it occurs. We aimed to establish snoozing as a construct in need of additional study.

Methods

A novel survey examined snoozing prevalence, how snoozing was accomplished, and explored possible contributors and motivators of snoozing behavior in 450 participants. Trait- and day-level surveys were combined with wearable data to determine if snoozers sleep differently than nonsnoozers, and how snoozers and nonsnoozers differ in other areas, such as personality.

Results

57% of participants snoozed. Being female, younger, having fewer steps, having lower conscientiousness, having more disturbed sleep, and being a more evening chronotype increased the likelihood of being a snoozer. Snoozers had elevated resting HR and showed lighter sleep before waking. Snoozers did not sleep less than nonsnoozers nor did they feel more sleepiness or nap more often.

Conclusions

Snoozing is a common behavior associated with changes in sleep physiology before waking, both in a trait- and state-dependent manner, and is influenced by demographic and behavioral traits. Additional research is needed, especially in detailing the physiology of snoozing, its impact on health, and its interactions with observational studies of sleep.

Mental Health of Canadian Firefighters: The Impact of Sleep

Volunteer and career firefighters are at risk of major depressive disorders, posttraumatic stress disorder (PTSD), alcohol use disorder, and other mental health disorders due to the demanding and unpredictable nature of their employment. The mental health risks are exacerbated by the need to work extended hours, night shifts, and/or rotating schedules, or the competing demands of other employment, especially in volunteer firefighters. The mental health disorders and risk factors interact with altered sleeping patterns. In the current study, we examined volunteer and career firefighters regarding the association between mental health and sleep, drawing from a national Canadian mental health survey of 1217 firefighters. Most (69%) of the firefighters reported less than ideal sleep quality and 21% screened positive for clinical insomnia, with no significant difference between volunteer and career subgroups. Firefighters with insomnia had higher odds ratios (OR) and frequencies for PTSD (OR = 4.98), generalized anxiety disorder (OR = 7.15), panic disorder (OR = 6.88), social phobia (OR = 4.98), and major depressive disorder (OR = 7.91), than firefighters without insomnia. The burden of sleep disorders and their association with mental health disorders suggests that sleep should be considered in health monitoring and self-management, environmental design, fire service work-organization policies, and health programming.

Verification methodology for Smart Awakening Systems

A mental and physical recovery after an awakening moment depends not only on the overall sleep duration and quality but mostly on the sleep stage in the waking moment. The most comfortable awakening moment is during the Light or Wake sleep stages. But the fix-time alarm clock doesn't take into account the sleep stage in the awakening moment, which often results in awakening during the Deep or Rapid Eyes Movement stages. To reduce the negative recovery effect, big companies and research groups develop various awakening systems. Such systems recognize sleep stages based on wearable sensors' data (mostly from accelerometer sensors) and thus can find the easiest awakening moment time with minimal recovery effects.However, it is quite hard to measure and verify the efficiency of such systems without using polysomnography (which can be performed only in clinical conditions by medical experts). To solve this problem we developed a methodology based on questionnaires and psychological tests. Such an approach has big scalability, does not require special medical equipment, and can be evaluated in a home environment with minimal support effort. The proposed verification approach has been tested on smartwatches with the sleep stages forecast model. The proposed model accuracy was 78%. Results of our experiment show that the majority of users demonstrated a correlation between awakening quality and the verification tests performance.

Psychophysiological responses of firefighters to day and night rescue interventions

This study aimed 1) to assess the psychophysiological responses throughout a rescue intervention performed during the day and at night and 2) to determine if a vibrating alarm influences these psychophysiological responses at night. Sixteen male firefighters completed a simulated intervention under three different conditions: 1) during the day with a sound alarm signal (Day_SA), 2) during the night with a sound alarm signal (Night_SA), 3) during the night with a vibrating alarm signal (Night_VA). Cardiovascular and psychological stress were recorded throughout the interventions. During the alarm signal, HR reactivity was greater in Night_SA than in Day_SA (p < 0.01). Parasympathetic reactivation and self-confidence were significantly lower in Night_SA than in Day_SA (p < 0.05). HR reactivity was decreased in Night_VA in comparison to Night_SA (p < 0.05). Overall, the rescue intervention had a greater impact on the psychophysiological variables during the night than during the day, and the type of alarm had a minor effect.

Associations between sleep, stress, and cardiovascular health in emergency medical services personnel

OBJECTIVE

Our objective was to quantify the associations between sleep duration and perceived and chronic stress with ideal cardiovascular health (CVH) among emergency medical services (EMS) personnel from county-based EMS agencies.

METHODS

We conducted a cross-sectional survey of cardiovascular disease (CVD)-free EMS personnel from 4 US EMS agencies. The questionnaire consisted of the Pittsburgh Sleep Quality Index (PSQI), Perceived Stress Scale (PSS), Chronic Burden Scale, and the CVH components (smoking, body mass index, physical activity, diet, blood glucose, blood pressure, cholesterol, each scored 0-2 points). The components were summed and ideal CVH considered 11-14 points. Mixed effects logistic regression models with a random intercept for agency were used to estimate the odds of ideal CVH for good sleep quality (PSQI < 5 points), recommended sleep duration (7 to < 9h), low perceived stress (PSS < 26 points), and low chronic stress (0 recent stressful events).

RESULTS

We received 379 responses (response rate = 32%). There was low prevalence of good sleep quality (23%) and recommended sleep duration (25%), but 95% reported low perceived stress, and 33% had low chronic stress. Ideal CVH was reported by 30%. No significant associations between ideal CVH and sleep quality, perceived stress, or chronic stress were found. There was a nearly 2-fold increase in the odds of ideal CVH with recommended sleep duration (odds ratio: 1.83, 95% confidence interval: 1.08-3.10).

CONCLUSION

In this sample of EMS personnel, only recommended sleep duration was associated with ideal CVH. Future longitudinal studies are needed to understand the relationship between sleep, stress, and CVD in this understudied occupational group.

Heart rate response to alarm tones in firefighters

OBJECTIVE

To examine cardiovascular responses to medical (MED) and fire (FIRE) alarm tones in firefighters.

METHODS

Heart rate was collected throughout 24-h shifts (N = 41). Call logs were utilized post hoc to identify heart rate at the time the alarm sounded (TIME_TONE), peak heart rate following the alarm (TIME_PEAK), and heart rate at the time of station departure (TIME_DEPART) for MED and FIRE calls. A 2X3 (TONE x TIME) split-plot mixed-model repeated-measures analysis of variance (ANOVA) and least significant differences tests examined the influence of tone type on heart rate, expressed as a percent of age estimated maximum. Bivariate Pearson correlations examined the relationship between body mass index (BMI) and TIME_PEAK and TIME_DEPART. An alpha of 0.05 determined statistical significance and Bonferroni Corrections were applied to post hoc comparisons (p < 0.017).

RESULTS

Follow-up analyses for the significant 2 × 3 repeated-measures ANOVA (p = 0.035) indicated differences in heart rate for MED (p < 0.001) and FIRE (p < 0.001) where TIME_TONE < TIME_PEAK, TIME_TONE < TIME_DEPART, and TIME_PEAK > TIME_DEPART. There was a non-significant simple effect of time for MED and FIRE at TIME_TONE (p = 0.259), but significant effects of tone type where FIRE > MED at TIME_PEAK (p < 0.001) and TIME_DEPART (p = 0.002). There was a significant small positive relationship between BMI and TIME_PEAK (p = 0.002) and TIME_DEPART (p < 0.001) for MED only.

CONCLUSIONS

Alarms increased heart rates to a greater extent in FIRE than MED calls. Higher BMI was related to greater heart rate responses in MED but was unrelated to FIRE response.

Acute stress impairs reward learning in men

Acute stress is ubiquitous in everyday life, but the extent to which acute stress affects how people learn from the outcomes of their choices is still poorly understood. Here, we investigate how acute stress impacts reward and punishment learning in men using a reinforcement-learning task. Sixty-two male participants performed the task whilst under stress and control conditions. We observed that acute stress impaired participants' choice performance towards monetary gains, but not losses. To unravel the mechanism(s) underlying such impairment, we fitted a reinforcement-learning model to participants' trial-by-trial choices. Computational modeling indicated that under acute stress participants learned more slowly from positive prediction errors - when the outcomes were better than expected - consistent with stress-induced dopamine disruptions. Such mechanistic understanding of how acute stress impairs reward learning is particularly important given the pervasiveness of stress in our daily life and the impact that stress can have on our wellbeing and mental health.

Using Logistic Regression to Identify Leading Factors to Prepare for an Earthquake Emergency during Daytime and Nighttime: The Case of Mass Earthquake Drills

Historical data have demonstrated that earthquakes can happen any time of the day and night. Drills may help communities to better prepare for such emergencies. A cross-sectional survey was conducted from 4 October to 20 November 2017, in Mexico City. The sample size was 2400. The addressed research questions were “what factors predict the likelihood that respondents would report that they agree on conducting mass evacuation drills: (a) any time of the day and (b) any time at night?” The logistic regression technique was employed to identify the factors leading to the outcome. In relation to (a), five variables were significantly associated with the outcome, i.e., age, frequency of drills, warning time, knowledge on what to do, and “perception vulnerability city”. Regarding (b), five variables were also significantly associated with the outcome variable, i.e., age, level of education, frequency of drills, negative emotions, and fear of house/building collapsing. More generally, several drills should be conducted any time of the day and night; further, 50% of them should be announced and 50% unannounced. Furthermore, the time of earthquake drills should be randomly selected. In this way, we may just match the spatial–temporal dimension of an earthquake emergency. It is hoped that the findings will lead to better preparedness of the residents of the capital city during an earthquake occurrence.

Exercising Caution Upon Waking-Can Exercise Reduce Sleep Inertia?

Sleep inertia, the transitional state of reduced alertness and impaired cognitive performance upon waking, is a safety risk for on-call personnel who can be required to perform critical tasks soon after waking. Sleep inertia countermeasures have previously been investigated; however, none have successfully dissipated sleep inertia within the first 15 min following waking. During this time, on-call personnel could already be driving, providing advice, or performing other safety-critical tasks. Exercise has not yet been investigated as a sleep inertia countermeasure but has the potential to stimulate the key physiological mechanisms that occur upon waking, including changes in cerebral blood flow, the cortisol awakening response, and increases in core body temperature. Here, we examine these physiological processes and hypothesize how exercise can stimulate them, positioning exercise as an effective sleep inertia countermeasure. We then propose key considerations for research investigating the efficacy of exercise as a sleep inertia countermeasure, including the need to determine the intensity and duration of exercise required to reduce sleep inertia, as well as testing the effectiveness of exercise across a range of conditions in which the severity of sleep inertia may vary. Finally, practical considerations are identified, including the recommendation that qualitative field-based research be conducted with on-call personnel to determine the potential constraints in utilizing exercise as a sleep inertia countermeasure in real-world scenarios.

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.

Overnight heart rate variability and next day cortisol response during simulated on-call conditions

OBJECTIVE

This study had two specific objectives, 1) to investigate the impact of being on-call on overnight heart rate variability during sleep and; 2) to examine whether being on-call overnight impacted next-day salivary cortisol concentrations.

METHODS

Data are reported from three within-subject laboratory studies (n = 24 in each study) that assessed varying on-call conditions. Healthy male participants (n = 72 total) completed a four-night laboratory protocol, comprising an adaptation night, a control night, and two counterbalanced on-call nights with varying on-call conditions. These on-call conditions were designed to determine the impact of, Study 1: the likelihood of receiving a call (definitely, maybe), Study 2: task stress (high-stress, low-stress), and Study 3: chance of missing the alarm (high-chance, low-chance), on measures of physiological stress. Overnight heart rate variability (HRV) (during sleep) was measured using two-lead electrocardiography, and time- and frequency-domain variables were analysed. Saliva samples were collected at 15-min time intervals from 0700-0800 h to determine cortisol awakening response outcomes and at four daily time points (0930 h, 1230 h, 1430 h, and 1730 h) to assess diurnal cortisol profiles.

RESULTS

There were few differences in HRV measures during sleep across all three studies. The only exception was in Study 1 where the standard deviation of the time interval between consecutive heartbeats and the root mean square of consecutive differences between heartbeats were lower across all sleep stages in the definitely condition, when compared to control. Across all three studies, being on-call overnight also had little impact on next-day cortisol awakening response (CAR), with the exception of Study 2 where the 1) CAR area under the curve with respect to increase was blunted in the high-stress condition, compared to the control and low-stress conditions and, 2) CAR reactivity was higher in low-stress condition, compared with the high-stress condition. In Study 1, diurnal cortisol area under the curve with respect to ground was lower in the on-call conditions (definitely and maybe) when compared to control. There were no differences in diurnal cortisol measures in Study 3.

CONCLUSION

This is the first study to investigate how different aspects of being on-call affect physiological stress responses. Overall, relatively little differences in measures of overnight heart rate variability and next-day cortisol response were recorded in all three studies. Further research utilising real on-call work tasks, not just on-call expectations (as in the current study) will help determine the impact of on-call work on the physiological stress response.

Salivary cortisol profiles of on-call from home fire and emergency service personnel

Working on-call with a night call resulted in a depressed (lower) cortisol awakening response (CAR) peak and post-awakening cortisol area under the curve with respect to ground (AUC_G) the following day compared to when off-call. This may be due to exposure to noise, physical exertion, and stressful events during night callouts. There was no anticipatory effect to working on-call in any of the cortisol measures examined. This study, of male fire and emergency service workers who operate on-call from home, had two aims: (1) examine CAR and diurnal cortisol profile following a night on-call with a call, on-call without a call, and off-call; and, (2) explore whether there is an anticipatory effect of working on-call from home on diurnal cortisol profiles. Participants wore activity monitors, completed sleep and work diaries and collected seven saliva samples a day (0 min, 30 min, 60 min, 3 h, 6 h, 9 h, and 12 h after final awakening) for one week. CAR peak, reactivity and area under the curve with respect to increase (AUC_I), post-awakening cortisol AUC_G, diurnal cortisol slope and AUC_G, and mean 12-h cortisol concentrations were calculated. The final analysis included 26 participants for Aim 1 (22 off-call nights, 68 nights on-call without a call, and 20 nights on-call with a call) and 14 participants for Aim 2 (25 days leading up to a night off-call and 92 days leading up to a night on-call). Generalized estimating equations models were constructed for each variable of interest. Aim 1: CAR peak and post-awakening cortisol AUC_G were 8.2 ± 3.4 nmol/L and 5.7 ± 2.4 units lower, respectively, following a night on-call with a call compared to an off-call night. Aim 2: the day before a night on-call was not a significant predictor in any model. The lower CAR peak and post-awakening cortisol AUC_G following a night on-call with a call compared to following an off-call night may be due to exposure to noise, physical exertion, and stressful events during night callouts. The lack of difference between the day before a night on-call and the day before an off-call night suggests there may not be an anticipatory effect on cortisol when on-call from home.

The inflammatory response to simulated day and night emergency alarm mobilisations

Purpose

Responding to emergency alarms is a daily occurrence for personnel in safety-critical occupations, and is associated with negative health outcomes in this population. The purpose of the present study was to determine the acute inflammatory response to an isolated emergency alarm mobilisation in both day and night conditions.

Methods

Sixteen healthy males (mean age 25 ± 4 years) spent four days and nights in a sleep laboratory and were required to mobilise to an emergency alarm either during the day (1558 h), or from nocturnal sleep (0358 h). Pro (TNF-α, IL-1β, IL-8, IL-6) and anti-inflammatory (IL-4 and IL-10) cytokine responses to each alarm mobilisation were compared to time-matched control conditions without the alarm and mobilisation stimulus.

Results

Analysis revealed no significant drift of cytokine levels at 1400 h across the study (P≥0.139). The plasma concentration of anti-inflammatory cytokine IL-4 was 84% greater in the 2-h sampling period following night alarm mobilisation compared to a night control of gentle awakening (P = 0.049), no other condition-by-time interactions were observed. The majority of inflammatory concentrations did not significantly change between alarm mobilisation and control conditions, in either day or night trials.

Conclusions

These findings may reflect the lack of a true emergency (and the perceived stress) for the alarm mobilisation, together with the neutralising effect of different circadian biorhythms on inflammatory cytokine concentrations.

Effects of simulated highway noise on heart rates of larval monarch butterflies, Danaus plexippus: implications for roadside habitat suitability

Developed countries around the world are criss-crossed with vast networks of roadways. Conservationists have recently focused attention on roadsides as possible locations for establishing pollinator habitat, with the monarch butterfly (Danaus plexippus) featuring prominently in such discussions. However, roadsides are inherently loud, which could negatively affect developing larvae. We conducted a series of experiments testing if simulated highway noise stresses monarch larvae, which we gauged by non-destructive monitoring of heart rates. In two replicated experiments, larvae exposed for 2 h experienced a significant increase in heart rate (16 and 17% elevation), indicating they perceive traffic noise as a stressor. Meanwhile, experiments exposing larvae for either 7 or 12 days to continuous traffic noise both showed no heart rate elevation at the end of larval development, suggesting chronic noise exposure leads to habituation or desensitization. Habituation to stress as larvae may impair reactions to real-world stressors as adults, which could be problematic for a butterfly that undertakes an annual two-month migration that is fraught with dangers. More generally, these results could have far-reaching implications for the billions of insects worldwide that develop near roadways, and argue that further study is needed before promoting roadside habitat for butterfly conservation.