Post-awakening Cortisol in Explosive Ordnance Disposal Technicians: A Replication Study in a Novel Population.

INTRODUCTION: Amassing evidence suggests that post-awakening salivary cortisol rhythms (changes in cortisol throughout the day) may indicate health status. We previously established summary parameters for salivary cortisol in U.S. Navy Sea, Air, and Land and reported excellent parameter stability across 2 days of repeated sampling. To confirm the generalizability of our original findings to other military populations, we replicated the procedures of our prior report in another specialized military group. The purpose of this study was to (1) establish summary parameters of daily salivary cortisol rhythms, (2) evaluate summary parameter stability, and (3) assess the impact of sampling compliance in U.S. Navy Explosive Ordnance Disposal (EOD) technicians. MATERIALS AND METHODS: Seventy active duty, male Explosive Ordnance Disposal technicians (mean ± SD age; 34.9 ± 6.5 years) self-collected saliva samples in a nondeployed setting on two consecutive weekdays at WAKE, WAKE + 30 min, WAKE + 60 min, 4 p.m., and 9 p.m. For salivary cortisol, we computed summary parameters, i.e., measures of magnitude and measures of pattern, and then evaluated their stabilities via correlational analyses and Cronbach's alpha (α). Compliance was objectively and subjectively evaluated using actigraphy and self-reported data, respectively. This research was conducted under a Naval Health Research Center Institutional Review Board approved study (NHRC.2015.0013). RESULTS: Average salivary cortisol concentrations increased at WAKE + 30 (mean ± SE reactivity; 48.9 + 6.8%) from WAKE, followed by a swift recovery at WAKE + 60. Approximately 10.9% of the group were classified as negative-responders (i.e., < 0% change from WAKE to WAKE + 30). The measures of magnitude demonstrated fair stability across two days (r value range: 0.37-0.45, ps < 0.01; α range: 0.54-0.62). Fifty-five percent of the sample was classified as compliant (defined as <15 min deviation from target sampling times) across both days. Compliance decreased to 31% when compliance criteria were refined to <5 min deviation; however, controlling for compliance did not overwhelmingly influence the more stable summary parameters of magnitude. CONCLUSIONS: These findings demonstrate a thorough replication, with some additional refinement, of our prior study, implying generalizability across diverse military populations. Study limitations include unsupervised saliva collection in a free-living setting, which is counterbalanced by ecological validity. The noninvasive salivary sampling protocol used in this study yields stable estimations of daily cortisol rhythms in specialized military men and is recommended as an operational health surveillance tool by which to monitor chronically stressed military members.

Anabolic hormone profiles in elite military men: Robust associations with age, stress, and fatigue.

We recently established stable daily profiles of the anabolic hormones dehydroepiandrosterone (DHEA) and testosterone in 57 elite military men. In this follow-on study, we explored associations of salivary anabolic hormone profiles with demographic (i.e., age, body mass index [BMI]) and biobehavioral health indices (i.e., blood pressure, sleep, perceived stress, fatigue) via correlational models. Next, nuanced patterns were constructed using quartile splits followed by one-way analysis of variance and post hoc subgroup comparisons. Both DHEA (r range: -0.33 to -0.49) and testosterone (r range: -0.19 to -0.41) were inversely associated with age. Quartile comparisons revealed that age-related declines in DHEA were linear, curvilinear, or sigmoidal, depending on the summary parameter of interest. Anabolic hormone profiles did not associate with BMI, blood pressure, or sleep efficiency. Robust linear associations were observed between testosterone and perceived stress (r range: -0.29 to -0.36); concentration-dependent patterns were less discernible. Lower DHEA (r range: -0.22 to -0.30) and testosterone (r range: -0.22 to -0.36) concentrations associated with higher fatigue. Subsequent quartile comparisons suggested a concentration-dependent threshold with respect to evening testosterone. Specifically, those individuals within the lowest quartile (≤68.4pg/mL) endorsed the highest fatigue of the four groups (p=0.01), while the remaining three groups did not differ from each other. This study not only showed that anabolic hormone profiles have distinctive age trajectories, but are also valuable predictors of stress and fatigue in elite military men. This highlights the importance of routine monitoring of anabolic hormone profiles to sustain and optimize health and readiness in chronically stressed populations.

Cortisol Awakening Response in Elite Military Men: Summary Parameters, Stability Measurement, and Effect of Compliance.

The cortisol awakening response (CAR) holds promise as a clinically important marker of health status. However, CAR research is routinely challenged by its innate complexity, sensitivity to confounds, and methodological inconsistencies. In this unprecedented characterization of CAR in elite military men (N = 58), we established summary parameters, evaluated sampling stability across two consecutive days, and explored the effect of subject compliance. Average salivary cortisol concentrations increased nearly 60% within 30 minutes of waking, followed by a swift recovery to waking values at 60 minutes. Approximately one in six were classified as negative responders (i.e., <0% change from waking to 30-minute postawakening). Three summary parameters of magnitude, as well as three summary parameters of pattern, were computed. Consistent with our hypothesis, summary parameters of magnitude displayed superior stability compared with summary parameters of pattern in the total sample. As expected, compliance with target sampling times was relatively good; average deviations of self-reported morning sampling times in relation to actigraph-derived wake times across both days were within ±5 minutes, and nearly two-thirds of the sample was classified as CAR compliant across both days. Although compliance had equivocal effects on some measures of magnitude, it substantially improved the stability of summary parameters of pattern. The first of its kind, this study established the foundation for a program of CAR research in a profoundly resilient yet chronically stressed population. Building from this, our forthcoming research will evaluate demographic, biobehavioral, and clinical determinants of CAR in this unique population.

Sex differences in coping strategies in military survival school.

A wealth of research has examined psychological responses to trauma among male military service members, but few studies have examined sex differences in response to trauma, such as coping strategies. This study assessed coping strategies used by male and female U.S. service members completing an intensely stressful mock-captivity exercise, compared strategies by sex, and assessed the relationship between coping and posttraumatic stress symptoms (PTSS). Two hundred service members (78% male) completed self-report surveys before and after mock captivity. Surveys assessed demographics, service characteristics, PTSS, and coping strategies used during mock captivity. Participants used seven coping strategies: denial, self-blame, religion, self-distraction, behavioral disengagement, positive reframing, and planning. Women used denial (p≤.05), self-blame (p≤.05), and positive reinterpretation (p≤.05) strategies more frequently than men, and they had higher PTSS levels following the exercise. Structural equation modeling showed that the relationship between sex and PTSS was fully mediated by coping strategies. The results of this study suggest that reducing the use of maladaptive coping strategies may mitigate PTSS among females. Future efforts should target improving coping during highly stressful and traumatic experiences.

Sex differences in cardiovascular and subjective stress reactions: prospective evidence in a realistic military setting.

Evidence points to heightened physiological arousal in response to acute stress exposure as both a prospective indicator and a core characteristic of posttraumatic stress disorder (PTSD). Because females may be at higher risk for PTSD development, it is important to evaluate sex differences in acute stress reactions. This study characterized sex differences in cardiovascular and subjective stress reactions among military survival trainees. One hundred and eighty-five military members (78% males) were studied before, during, and 24 h after stressful mock captivity. Cardiovascular (heart rate [HR], systolic blood pressure [SBP], diastolic blood pressure [DBP]) and dissociative states were measured at all three time points. Psychological impact of mock captivity was assessed during recovery. General linear modeling with repeated measures evaluated sex differences for each cardiovascular endpoint, and causal steps modeling was used to explore interrelationships among sex, cardiovascular reactions and psychological impact of mock captivity. Although females had lower SBP than males at all three time points, the difference was most pronounced at baseline and during stress. Accordingly, females showed greater residual elevation in SBP during recovery. Females had lower DBP at all three time points. In addition, females reported greater psychological impact of mock captivity than males. Exploratory causal steps modeling suggested that stress-induced HR may partially mediate the effect of sex on psychological impact of mock captivity. In conclusion, this study demonstrated sex-specific cardiovascular stress reactions in military personnel, along with greater psychological impact of stress exposure in females. This research may elucidate sex differences in PTSD development.

Effects of dehydroepiandrosterone supplementation during stressful military training: a randomized, controlled, double-blind field study.

Dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS) are anabolic prehormones involved in the synthesis of testosterone. Both have been shown to exert neuroprotective effects during stress. In this randomized, controlled, double-blind field study, we examined the effects of a 12-day DHEA regimen on stress indices in military men undergoing survival training. Forty-eight men were randomized to either a DHEA treatment group or placebo control group. The treatment group received 50 mg of oral DHEA supplementation daily for 5 days during classroom training followed by 7 days of 75 mg during stressful field operations. Control subjects received identical placebo pills. Salivary assays (DHEA[S], testosterone, and cortisol) were conducted at four time points: distal pre-stress (T1), proximal pre-stress (T2), mock-captivity stress (T3), and 24 h recovery (T4). Subjective distress was also assessed at T1, T3, and T4. As expected, DHEA treatment resulted in higher salivary concentrations of DHEA and DHEAS during daily living, mock-captivity stress, and recovery. Similar patterns were observed for salivary markers of anabolic balance: DHEA/cortisol, DHEAS/cortisol, and testosterone/cortisol concentration ratios. Despite notable time effects, no group differences emerged for subjective distress. A brief, low dose DHEA regimen yielded large increases in salivary DHEA(S) concentrations and enhanced anabolic balance throughout sustained military stress. These physiological changes did not extrapolate to subjective distress.

Effect of psychological skills training during military survival school: a randomized, controlled field study.

In this randomized, controlled field study, we examined the effects of a brief psychological skills training (PST) intervention on stress responses during military survival school. A second purpose was to build upon prior research in this unique environment by extending the follow-up window to 3 months. Baseline subjective distress (dissociative) symptoms were measured in 65 male military subjects, who were then randomized either to PST or a control group that received no training beyond the normal survival school curriculum. PST received training in arousal control, mental imagery, goal setting, and positive self-talk in two separate 40-minute sessions before stressful field exercises. Stress symptoms were then assessed during a mock-captivity phase of training, as well as 24 hours, 1 month, and 3 months after completion of training. Repeated-measures analyses of variance with follow-up paired t tests examined differences between groups and across time. Survival training precipitated remarkable increases in subjective distress, but few substantive group differences emerged. This study extends prior work quantifying the human stress response to intense military training.

Anger expression and stress responses in military men.

INTRODUCTION: A better understanding of individual differences in the human stress response may enhance prevention and treatment of operational stress reactions. In this study, we examined the relationships of anger experience and expression to stress indices during daily living and in response to military survival training in 45 men. METHODS: Prior to participation in survival training, subjects completed self-report measures of perceived stress and anger. The revised Impact of Event Scale was then administered 24 h after the conclusion of training. RESULTS: As expected, outward anger expression was positively associated with perceived stress during free living (P < 0.0125). Outward anger expression, inward anger expression, and angry temperament then combined to account for 25% of the variance in psychological impact of a stressful mock-captivity challenge. CONCLUSION: Anger characteristics are associated with human stress endpoints, both during daily living and in response to an ecologically valid stressor. These findings may assist in the prevention and treatment of operational stress reactions.

Behavioral predictors of acute stress symptoms during intense military training.

A better understanding of factors influencing human responses to acute stress is needed to enhance prevention and treatment of stress-related disorders. In the current study, the authors examined predictors of acute stress symptoms during intense military training in 35 men. In univariate and multivariate models, perceived stress, passive coping, and emotion-focused coping during daily living predicted acute stress symptoms in response to realistic survival training, whereas active coping and problem-focused coping did not. Baseline stress levels and coping styles, both of which may be modifiable, appear to play a fundamental role in the human response to acute uncontrollable stress. Additional research is needed to better elucidate the relative and interactive contributions of behavioral predictors of acute stress.

A neuroscience approach to optimizing brain resources for human performance in extreme environments.

Extreme environments requiring optimal cognitive and behavioral performance occur in a wide variety of situations ranging from complex combat operations to elite athletic competitions. Although a large literature characterizes psychological and other aspects of individual differences in performances in extreme environments, virtually nothing is known about the underlying neural basis for these differences. This review summarizes the cognitive, emotional, and behavioral consequences of exposure to extreme environments, discusses predictors of performance, and builds a case for the use of neuroscience approaches to quantify and understand optimal cognitive and behavioral performance. Extreme environments are defined as an external context that exposes individuals to demanding psychological and/or physical conditions, and which may have profound effects on cognitive and behavioral performance. Examples of these types of environments include combat situations, Olympic-level competition, and expeditions in extreme cold, at high altitudes, or in space. Optimal performance is defined as the degree to which individuals achieve a desired outcome when completing goal-oriented tasks. It is hypothesized that individual variability with respect to optimal performance in extreme environments depends on a well "contextualized" internal body state that is associated with an appropriate potential to act. This hypothesis can be translated into an experimental approach that may be useful for quantifying the degree to which individuals are particularly suited to performing optimally in demanding environments.

Physical fitness influences stress reactions to extreme military training.

BACKGROUND: Physical fitness and physical conditioning have long been valued by the military for their roles in enhancing mission-specific performance and reducing risk of injury in the warfighter. It is not known whether physical fitness plays a causal role in attenuating acute military stress reactions or the evolution of post-traumatic stress disorder. OBJECTIVE: The objective of this study was to determine whether physical fitness influences the impact of stressful events during military survival training in 31 men. METHODS: Participants self-reported their most recent Physical Readiness Test scores and completed a trait anxiety measure before survival training. Participants also completed the Impact of Events Scale (IES) 24 hours after training. RESULTS: Aerobic fitness was inversely associated with the total IES score (p < 0.01, adjusted R2 = 0.19). When adjusted for trait anxiety, this relationship was substantially attenuated and no longer significant (p = 0.11). Trait anxiety was inversely associated with aerobic fitness (p < 0.05) and positively related to IES (p < 0.001). CONCLUSIONS: Physical fitness may buffer stress symptoms secondary to extreme military stress and its effects may be mediated via fitness-related attenuations in trait anxiety.

Trait anxiety and salivary cortisol during free living and military stress.

INTRODUCTION: Accumulating evidence suggests that negative affect is associated with elevated cortisol. Limited research has investigated this association in young, highly functioning, and stress-resilient populations. METHODS: We examined the relation of trait anxiety with total and diurnal salivary cortisol during free-living conditions and during a stressful military exercise in 26 military men ages 19-30 yr (M = 21.6, SD = 2.3). Salivary cortisol was assessed at five time points over 2 consecutive days of free-living measurement, and three time points during a stressful military experience. Trait anxiety was measured with the trait portion of the Spielberger State-Trait Anxiety Inventory 1-3 wk prior to the military exercise. RESULTS: Total cortisol concentrations were similar between men reporting high or low anxiety during free-living conditions (8.6 +/- 3.2 vs. 7.4 +/- 2.8 nmol x L(-1), respectively, P > 0.05), and military stress (21.3 +/- 7.3 vs. 19.0 +/- 7.0 nmol x L(-1), respectively, P > 0.05). The diurnal cortisol profile differed significantly (P = 0.04) between these men during the free-living condition, but not the stressful military experience (P > 0.05). Specifically, during free living, men with low anxiety exhibited a diurnal cortisol pattern that peaked in the early morning, decreased precipitously during the midmorning, and continued to decrease throughout the day, reaching a nadir in the evening. By contrast, the cortisol pattern of high-anxiety men remained elevated and significantly higher than their low-anxiety counterparts during the midmorning, decreased more slowly throughout the day, and reached its lowest level in the evening. Results were not substantially altered following adjustment for sleep duration or wake time. CONCLUSION: These findings suggest that trait anxiety influences the diurnal cortisol pattern in young, apparently healthy men during free-living conditions, but does not predict the cortisol response to uncontrollable military stress.

Stressful military training: endocrine reactivity, performance, and psychological impact.

INTRODUCTION: We examined the responsiveness of both cortisol and dehydroepiandrosterone sulfate (DHEAS) to the stress of survival training in military men and evaluated relationships to performance, peritraumatic dissociation, and the subsequent impact of stressful events. METHODS: Baseline salivary cortisol samples were self-collected by 19 men at 0900 and 1930 in a free-living (FL) environment. DHEAS samples were also collected in a subset of this sample (N = 12). Samples were subsequently taken at similar time points during a stressful captivity (SC) phase of training. Repeated-measures analyses of variance with follow-up paired t-tests examined differences across time and conditions. RESULTS: Significant increases were observed at both time points (0900 and 1930) from FL to SC in both cortisol (0900: 9.2 +/- 3.4 nmol x L(-1) vs. 18.4 +/- 10.5 nmol x L(-1); 1930: 3.5 +/- 3.0 nmol x L(-1) vs. 27.7 +/- 10.9 nmol x L(-1)) and DHEAS (0900: 1.7 +/- 1.3 ng x ml(-1) vs.6.7 +/- 3.5 ngx ml(-1); 1930: 1.5 0.84 ng x ml(-1) vs. 4.5 +/- 3.0 ng x ml(-1)). Also, overall performance during a high-intensity captivity-related challenge was inversely related to the DHEAS-cortisol ratio; conversely, overall performance during a low-intensity captivity-related challenge was positively related to DHEAS at the 0900 time point during SC. Dissociation was unrelated to endocrine indices measured during SC, while total impact of events was inversely related to percent change in DHEAS from FL to SC. CONCLUSIONS: Cortisol and DHEAS increase in response to allostatic load, and may relate to human performance during SC as well as PTSD symptoms.