Is high salt intake inducing obesity via production of cortisol? A novel working hypothesis and pilot study.

PURPOSE: Evidence is growing that high salt intake is an independent risk factor for obesity, but the mechanisms are unknown. Our novel working hypothesis is that high salt intake drives cortisol production, which in turn, drives obesity. The current study aimed to demonstrate an acute cortisol response following a single high salt meal. METHODS: Eight participants (age 30.5 ± 9.8 years [mean ± SD], 50% female), consumed high salt (3.82 g; 1529 mg sodium) and low salt (0.02 g; 9 mg sodium) meals in a randomized cross-over design. RESULTS: Urinary and salivary cortisol and plasma adrenocorticotropic hormone (ACTH) demonstrated order effects. When high salt was given second, there was a peak above baseline for urinary cortisol (26.3%), salivary cortisol (9.4%) and plasma ACTH (4.1%) followed by a significant decline in each hormone (treatment*time, F[9, 18] = 2.641, p = 0.038, partial η2 = 0.569; treatment*time, F[12, 24] = 2.668, p = 0.020, partial η2 = 0.572; treatment*time, F[12, 24] = 2.580, p = 0.023, partial η2 = 0.563, respectively), but not when high salt was given first (p > 0.05 for all). CONCLUSION: These intriguing findings provide partial support for our hypothesis and support a need for further research to elucidate the role of high salt intake in cortisol production and, in turn, in the aetiology of obesity. TRIAL REGISTRATION NUMBER: ACTRN12623000490673; date of registration 12/05/2023; retrospectively registered.

Low-dose adjuvant dexmedetomidine did not decrease propofol sedation requirements in children undergoing gastrointestinal endoscopy.

BACKGROUND: Propofol is the cornerstone of deep sedation during pediatric esophagogastroduodenoscopy (EGD), though adjuvant dexmedetomidine may provide propofol-sparing benefits. OBJECTIVE: The objective of the study was to evaluate whether adjuvant dexmedetomidine decreases the total propofol dose in pediatric patients undergoing EGD. METHODS: This single-center, retrospective, cohort study evaluated the total propofol dose in pediatric patients undergoing EGD with and without the use of adjuvant dexmedetomidine. Secondary outcomes included the change in hemodynamics across the perioperative continuum and post-procedure recovery time. A multivariable general linear regression was performed to identify associated variables for recovery time post-procedure. RESULTS: A total of 159 patients were included in the study; 88 patients received dexmedetomidine and propofol (DEX-PRO), and 71 patients received propofol only (PRO). The median [interquartile range (IQR)] propofol dose in the DEX-PRO group was 0.26 [IQR, 0.17-0.36] mg kg-1  min-1 which was not significantly different than the PRO group at 0.27 [IQR, 0.21-0.34] mg kg-1  min-1 , p = 0.730. Evaluation of secondary end points showed the DEX-PRO group had more cases of post-anesthesia care unit (PACU) hypotension (61% vs. 34%, p = 0.001) and a longer recovery time (32.9 ± 14.1 vs. 25.6 ± 10.8 min, p < 0.001) versus the PRO group, respectively. Multivariable linear regression demonstrated that age and the use of dexmedetomidine were associated with prolonged recovery. CONCLUSION: Adjuvant dexmedetomidine did not reduce propofol requirements compared with propofol alone in pediatric patients undergoing EGD. More hypotension and a longer postoperative recovery time were also seen in patients receiving adjuvant dexmedetomidine for their endoscopic procedure.

Psychological stress reactivity and future health and disease outcomes: A systematic review of prospective evidence.

BACKGROUND: Acute psychological stress activates the sympatho-adrenal medullary (SAM) system and hypothalamo-pituitary adrenal (HPA) axis. The relevance of this stress reactivity to long-term health and disease outcomes is of great importance. We examined prospective studies in apparently healthy adults to test the hypothesis that the magnitude of the response to acute psychological stress in healthy adults is related to future health and disease outcomes. METHODS: We searched Medline Complete, PsycINFO, CINAHL Complete and Embase up to 15 Aug 2019. Included studies were peer-reviewed, English-language, prospective studies in apparently healthy adults. The exposure was acute psychological stress reactivity (SAM system or HPA axis) at baseline. The outcome was any health or disease outcome at follow-up after ≥1 year. RESULTS: We identified 1719 papers through database searching and 1 additional paper through other sources. Forty-seven papers met our criteria including 32,866 participants (range 30-4100) with 1-23 years of follow-up. Overall, one third (32 %; 83/263) of all reported findings were significant and two thirds (68 %; 180/263) were null. With regard to the significant findings, both exaggerated (i.e. high) and blunted (i.e. low) stress reactivity of both the SAM system and the HPA axis at baseline were related to health and disease outcomes at follow-up. Exaggerated stress reactivity at baseline predicted an increase in risk factors for cardiovascular disease and decreased telomere length at follow-up. In contrast, blunted stress reactivity predicted future increased adiposity and obesity, more depression, anxiety and PTSD symptoms, greater illness frequency, musculoskeletal pain and regulatory T-Cell percentage, poorer cognitive ability, poorer self-reported health and physical disability and lower bone mass. CONCLUSION: Exaggerated and blunted SAM system and HPA axis stress reactivity predicted distinct physical and mental health and disease outcomes over time. Results from prospective studies consistently indicate stress reactivity as a predictor for future health and disease outcomes. Dysregulation of stress reactivity may represent a mechanism by which psychological stress contributes to the development of future health and disease outcomes.

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.

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-1ß, 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.

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 (AUCG) 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 (AUCI), post-awakening cortisol AUCG, diurnal cortisol slope and AUCG, 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 AUCG 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 AUCG 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.

Postpartum Tubal Sterilization: Making the Case for Urgency.

The parturient who requests postpartum sterilization has given consideration to and has made decisions regarding this aspect of her medical care long before her delivery. She arrives at parturition expecting the postpartum procedure to be performed as intended. The American Congress of Obstetricians and Gynecologists has reaffirmed its opinion that postpartum sterilization is an urgent procedure, owing to the safety and superior effectiveness of tubal sterilization via minilaparotomy in the immediate postpartum period, and the adverse consequences for mothers, babies, and society when the procedure is not actualized as desired and intended. In contrast, recent practice guidelines for obstetric anesthesia address anesthetic procedural aspects and short-term safety but overlook the long-term complications and considerations associated with failure to perform postpartum sterilization as planned. In practice, procedure completion rates are strikingly low, reportedly ranging from 31% to 52%. Reasons for failure to complete abound and include inadequate resources or inavailability of necessary personnel; obstetrician reluctance due to concerns for patient regret in younger women or medical comorbidities; barriers related to provision of obstetric care in a religiously affiliated hospital, or incomplete, improperly completed, or unavailable original federal consent forms among Medicaid-insured women. The federal requirement to wait 30 days after signing informed consent, and to retain the original signed document to be physically verified at time of the procedure, serves as a significant source of health care disparity for Medicaid-dependent mothers. This article reviews these larger issues of maternal health and comprehensive maternal care to broaden the anesthesiologist's appreciation of major benefits and potential risks of postpartum sterilization, including long-term effects, to promote an evidence-based, informed, and proactive role in delivering equitable, safe, and optimal care for these patients.

Salivary alpha amylase in on-call from home fire and emergency service personnel.

The effect of working on-call from home on the sympatho-adrenal medullary system activity is currently unknown. This study had two aims, Aim 1: examine salivary alpha amylase awakening response (AAR) and diurnal salivary alpha amylase (sAA) profile in fire and emergency service workers who operate on-call from home following a night on-call with a call (NIGHT-CALL), a night on-call without a call (NO-CALL) and an off-call night (OFF-CALL), and Aim 2: explore whether there was an anticipatory effect of working on-call from home (ON) compared to when there was an off-call (OFF) on the diurnal sAA profile. Participants wore activity monitors, completed sleep and work diaries and collected seven saliva samples a day for one week. AAR area under the curve with respect to ground (AUCG), AAR area under the curve with respect to increase (AUCI), AAR reactivity, diurnal sAA slope, diurnal sAA AUCG and mean 12-h sAA concentrations were calculated. Separate generalised estimating equation models were constructed for each variable of interest for each aim. For Aim 1, there were no differences between NIGHT-CALL or NO-CALL and OFF-CALL for any response variable. For Aim 2, there was no difference between any response variable of interest when ON the following night compared to when OFF the following night (n = 14). These findings suggest that there is no effect of working on-call from home on sAA, but should be interpreted with caution, as overnight data were not collected. Future research, using overnight heart rate monitoring, could help confirm these findings.

The effect of working on-call on stress physiology and sleep: A systematic review.

On-call work is becoming an increasingly common work pattern, yet the human impacts of this type of work are not well established. Given the likelihood of calls to occur outside regular work hours, it is important to consider the potential impact of working on-call on stress physiology and sleep. The aims of this review were to collate and evaluate evidence on the effects of working on-call from home on stress physiology and sleep. A systematic search of Ebsco Host, Embase, Web of Science, Scopus and ScienceDirect was conducted. Search terms included: on-call, on call, standby, sleep, cortisol, heart rate, adrenaline, noradrenaline, nor-adrenaline, epinephrine, norepinephrine, nor-epinephrine, salivary alpha amylase and alpha amylase. Eight studies met the inclusion criteria, with only one study investigating the effect of working on-call from home on stress physiology. All eight studies investigated the effect of working on-call from home on sleep. Working on-call from home appears to adversely affect sleep quantity, and in most cases, sleep quality. However, studies did not differentiate between night's on-call from home with and without calls. Data examining the effect of working on-call from home on stress physiology were not sufficient to draw meaningful conclusions.

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

The purpose of this study was to investigate the acute physiological stress response to an emergency alarm and mobilization during the day and at night. Sixteen healthy males aged 25 ± 4 years (mean ± SD) spent four consecutive days and nights in a sleep laboratory. This research used a within-participants design with repeated measures for time, alarm condition (alarm or control), and trial (day or night). When an alarm sounded, participants were required to mobilize immediately. Saliva samples for cortisol analysis were collected 0 min, 15 min, 30 min, 45 min, 60 min, 90 min, and 120 min after mobilization, and at corresponding times in control conditions. Heart rate was measured continuously throughout the study. Heart rate was higher in the day (F(20,442) = 9.140, P < 0.001) and night (F(23,459) = 8.356, P < 0.001) alarm conditions compared to the respective control conditions. There was no difference in saliva cortisol between day alarm and day control conditions. Cortisol was higher (F(6,183) = 2.450, P < 0.001) following the night alarm and mobilization compared to the night control condition. The magnitude of difference in cortisol between night control and night alarm conditions was greater (F(6,174) = 4.071, P < 0.001) than the magnitude of difference between the day control and day alarm conditions. The augmented heart rate response to the day and night alarms supports previous observations in field settings. Variations in the cortisol responses between conditions across the day and night may relate to differences in participants' ability to interpret the alarm when sleeping versus when awake.

On-call work: To sleep or not to sleep? It depends.

On-call working time arrangements are increasingly common, involve work only in the event of an unpredictable incident and exist primarily outside of standard hours. Like other non-standard working time arrangements, on-call work disrupts sleep and can therefore have negative effects on health, safety and performance. Unlike other non-standard working time arrangements, on-call work often allows sleep opportunities between calls. Any sleep obtained during on-call periods will be beneficial for waking performance. However, there is evidence that sleep while on call may be of substantially reduced restorative value because of the expectation of receiving the call and apprehension about missing the call. In turn, waking from sleep to respond to a call may be associated with temporary increases in performance impairment. This is dependent on characteristics of both the preceding sleep, the tasks required upon waking and the availability and utility of any countermeasures to support the transition from sleep to wake. In this paper, we critically evaluate the evidence both for and against sleeping during on-call periods and conclude that some sleep, even if it is of reduced quality and broken by repeated calls, is a good strategy. We also note, however, that organisations utilising on-call working time arrangements need to systematically manage the likelihood that on-call sleep can be associated with temporary performance impairments upon waking. Given that the majority of work in this area has been laboratory-based, there is a significant need for field-based investigations of the magnitude of sleep inertia, in addition to the utility of sleep inertia countermeasures. Field studies should include working with subject matter experts to identify the real-world impacts of changes in performance associated with sleeping, or not sleeping, whilst on call.

Sleep quantity and quality is not compromised during planned burn shifts of less than 12 h.

Planned burning is a preventative strategy aimed at decreasing fuel loads to reduce the severity of future wildfire events. During planned burn operations, firefighters can work long shifts. Furthermore, remote burning locations may require firefighters to sleep away from home between shifts. The existing evidence surrounding firefighters' sleep during such operations is exclusively anecdotal. The aims of the study were to describe firefighters' sleep during planned burn operations and evaluate the impact of the key operational factors (shift start time, shift length and sleeping location) that may contribute to inadequate sleep. Thirty-three salaried firefighters were recruited from Australia's fire agencies and sleep was measured objectively using wrist actigraphy for four weeks. All variables were examined in two conditions: (1) burn days, and (2) non-burn days. Time in bed, total sleep time, sleep latency and sleep efficiency were evaluated objectively. Subjective reports of pre- and post-sleep fatigue, sleep location, sleep quality, sleep quantity, number of times woken and sleep timing were also recorded. Analyses revealed no differences in measures of sleep quantity and quality when comparing non-burn and burn days. Total sleep time was less when planned burn shifts were >12 h. However, on burn days, work shift start time as well as sleeping location did not impact firefighters' sleep quantity. Self-reported levels of pre- and post-sleep fatigue were greater on burn days compared to non-burn days. These findings indicate that sleep quantity and quality are not compromised during planned burn operations <12 h in duration.

Fighting fire and fatigue: sleep quantity and quality during multi-day wildfire suppression.

This study examined firefighters' sleep quantity and quality throughout multi-day wildfire suppression, and assessed the impact of sleep location, shift length, shift start time and incident severity on these variables. For 4 weeks, 40 volunteer firefighters' sleep was assessed using wrist actigraphy. Analyses revealed that the quantity of sleep obtained on fire days was restricted, and pre- and post-sleep fatigue ratings were higher, compared to non-fire days. On fire days, total sleep time was less when: (i) sleep location was in a tent or vehicle, (ii) shifts were greater than 14 h and (iii) shifts started between 05:00 and 06:00 h. This is the first empirical investigation providing objective evidence that firefighters' sleep is restricted during wildfire suppression. Furthermore, sleep location, shift length and shift start time should be targeted when designing appropriate controls to manage fatigue-related risk and preserve firefighters' health and safety during wildfire events. Practitioner Summary: During multi-day wildfire suppression, firefighters' sleep quantity was restricted, and pre- and post-sleep fatigue ratings were higher, compared to non-fire days. Furthermore, total sleep time was less when: (i) sleep occurred in a tent/vehicle, (ii) shifts were >14 h and (iii) shifts started between 05:00 and 06:00 h.