Timing the end of nocturnal sleep

The Cortisol Awakening Response: Regulation and Functional Significance

In healthy individuals, the majority of cortisol secretion occurs within several hours surrounding morning awakening. A highly studied component of this secretory period is the cortisol awakening response (CAR), the rapid increase in cortisol levels across the first 30 to 45 minutes after morning awakening. This strong cortisol burst at the start of the active phase has been proposed to be functional in preparing the organism for the challenges of the upcoming day. Here, we review evidence on key regulatory and functional processes of the CAR and develop an integrative model of its functional role. Specifically, we propose that, in healthy individuals, the CAR is closely regulated by an intricate dual-control system, which draws upon key circadian, environmental, and neurocognitive processes to best predict the daily need for cortisol-related action. Fine-tuned CAR expression, in turn, is then assumed to induce potent glucocorticoid action via rapid nongenomic and slower genomic pathways (eg, affecting circadian clock gene expression) to support and modulate daily activity through relevant metabolic, immunological, and neurocognitive systems. We propose that this concerted action is adaptive in mediating two main functions: a primary process to mobilize resources to meet activity-related demands and a secondary process to help the organism counterregulate adverse prior-day emotional experiences.

Awakening not associated with an increased rate of cortisol secretion

Cortisol is released upon activation of the hypothalamic-pituitary-adrenal axis, varies across the day, possesses an underlying diurnal rhythm and is responsive to stressors. The endogenous circadian peak of cortisol occurs in the morning, and increases in cortisol observed post-awakening have been named the cortisol awakening response (CAR) based on the belief that the act of waking up stimulates cortisol secretion. However, objective evidence that awakening induces cortisol secretion is limited. We used a mixed effects model with a linear spline fitted to the data to examine tissue-free cortisol measurements obtained from 201 healthy volunteers by automated ambulatory microdialysis before and after awakening in their home environments. We also examined rate of change of cortisol depending on sleep duration and relative timing. We found no evidence for a change in the rate of cortisol increase in the hour after waking when compared with the hour prior to waking. We instead observed substantial interindividual variability in the absolute concentration and rate of change of cortisol levels, and differences in dynamics that may be attributable to duration and relative timing of sleep. Based on these results, we strongly suggest caution is needed when interpreting cortisol measurements solely obtained in the hour after waking.

"I was more conscious than usual, I wanted to get it right "

Cortisol awakening response (CAR) research relies upon self-collected saliva sampling during the post-awakening period. It is unknown how the CAR protocol is perceived and how they may affect typical routines relevant to CAR methodology. CAR assessment is sensitive to state variables, suggesting that CAR measurement may be affected by research participation. This is the first qualitative study to explore motivation and experiences of participation in CAR research. Interviews were conducted with a sample of 20 participants (males/females: 4/16) aged 46-82 years following their participation in CAR research in the domestic setting. Responses were transcribed verbatim and thematically analysed. Participants were motivated to take part in CAR research for altruistic reasons and the apparent convenience of undertaking the study at home. Participants experienced the study as arduous describing apprehension and the cognitive burden it placed on them leading to disruptions to sleep and morning routines. Participants also struggled to identify the moment of awakening and there was uncertainty surrounding the timing of the first awakening sample. Disruptions were lessened with habituation to sampling on repeated study days. There was apprehension about taking part in CAR research, affecting mood, cognition, and sleep; state variables known to influence the CAR. Findings inform ways to optimise CAR 'ecological validity' and obtain typical CAR characteristics. The 'moment of awakening', was not universally understood, leading to hesitancy in deciding when to collect saliva samples. Researchers need to include a specific discussion of the commonly experienced ambiguity surrounding awakening to increase awareness, lessen anxiety and highlight its importance.

Subjective sleep onset latency is influenced by sleep structure and body heat loss in human subjects

The present study examined the relationship between subjective sleep onset latency (SOL), sleep structure, changes in skin and body temperature, and subjective evaluation of sleep in healthy young adults to elucidate the pathophysiological mechanisms of insomnia. A total of 28 participants (age 21.54 [0.50] years) with no sleep problems participated in a 1-h polysomnographic recording that obtained objective sleep parameters during the daytime while skin and body temperatures were recorded. The distal-proximal skin temperature gradient (DPG) was calculated. Subjective parameters, such as subjective SOL, sleep time, and restorative sleepiness, were evaluated before and after sleep. Most participants estimated their sleep latency as being longer than their actual SOL (13.7 versus 7.6 min). Objective SOL was significantly correlated with each sleep stage parameter whereas subjective SOL was negatively correlated with Stage N2 sleep duration (Rho = -0.454, p = 0.020), slow-wave activity and delta power (Rho = -0.500, p = 0.011 and Rho = -0.432, p = 0.031, respectively), and ΔDPG (the degree of reduction of heat loss before and after lights-off). Stepwise regression analysis showed that ΔDPG was the strongest predictive factor in explaining the length of subjective SOL. The degree of heat dissipation before and after lights-off contributed most to the sensation of falling asleep in healthy young adults. This finding may be helpful for elucidating the physiological mechanisms of insomnia and its treatment.

Adaptive Effects of Endocrine Hormones on Metabolism of Macronutrients during Fasting and Starvation: A Scoping Review

Food deprivation can occur for different reasons. Fasting (<24 h duration) occurs to meet religious or well-being goals. Starvation (>1-day duration) occurs when there is intentional (hunger strike or treatment of a medical condition) or unintentional (anorexia nervosa, drought, epidemic famine, war, or natural disaster) food deprivation. A scoping review was undertaken using the PubMed database to explore 1805 abstracts and review 88 eligible full-text articles to explore the adaptive relationships that emerge between cortisol, insulin, glucagon, and thyroid hormones on the metabolic pathways of macronutrients in humans during fasting and starvation. The collected data indicate that fasting and starvation prime the human body to increase cortisol levels and decrease the insulin/glucagon ratio and triiodothyronine (T3) levels. During fasting, increased levels of cortisol and a decreased insulin/glucagon ratio enhance glycogenolysis and reduce the peripheral uptake of glucose and glycogenesis, whereas decreased T3 levels potentially reduce glycogenolysis. During starvation, increased levels of cortisol and a decreased insulin/glucagon ratio enhance lipolysis, proteolysis, fatty acid and amino acid oxidation, ketogenesis, and ureagenesis, and decreased T3 levels reduce thermogenesis. We present a potential crosstalk between T3 and the above hormones, including between T3 and leptin, to extend their adaptive roles in the metabolism of endogenous macronutrients during food deprivation.

Revisiting the Psychobiological Inhibition Model: a conceptual framework for understanding and treating insomnia using cognitive and behavioural therapeutics (CBTx)

Sleep is a biological imperative, so one might wonder "what has psychology got to do with it?" A person's behaviours, thoughts, emotions and interactions with the environment inevitably serve for good, or for ill, as the "setting conditions" for the expression of sleep. Put simply, although sleep is not a psychological phenomenon, sleep has crucial behavioural dependencies. Consequently, the Psychobiological Inhibition Model can embrace numerous, potentially interacting, pathways to the persistence of this ubiquitous disorder, providing an overarching conceptual framework for why and how insomnia develops. The clinical guideline treatment for chronic insomnia is cognitive behavioural therapy. Although typically delivered as "talking therapy", cognitive behavioural therapy is not some form of "psychobabble". Rather, the Psychobiological Inhibition Model framework for insomnia articulates how specific techniques can correct the various ways in which the expression of normal sleep and circadian brain-behaviour relationships have become disrupted. Indeed, cognitive behavioural therapy is best conceived of as an approach to treatment rather than being one specific agent. A shift in emphasis towards a cognitive and behavioural therapeutics formulary would provide improved impetus to understanding of how insomnia develops, and of how it may best be treated in any given patient.

Do diurnal salivary cortisol curves carry meaningful information about the regulatory biology of the HPA axis in healthy humans?

Salivary cortisol stress biomarkers have been extensively used in epidemiological work to document links between stress and ill health. There has been little effort to ground field friendly cortisol measures in the hypothalamic-pituitary-adrenal (HPA) axis regulatory biology that is likely relevant to delineating mechanistic pathways leading from stress exposure to detrimental health outcomes. Here, we utilized a healthy convenience sample (n = 140) to examine normal linkages between extensively collected salivary cortisol measures and available laboratory probes of HPA axis regulatory biology. Participants provided 9 saliva samples per day over 6 days within a month, while engaging in usual activities, and also participated in 5 regulatory tests (adrenocorticoptripin stimulation, dexamethasone/corticotropin-releasing-hormone stimulation, metyrapone, dexamethasone suppression, and Trier Social Stress Test). Logistical regression was used to test specific predictions linking cortisol curve components to regulatory variables and to explore widely for non-predicted associations. We found support for 2 of 3 original hypotheses, showing associations (1) between cortisol diurnal decline and feedback sensitivity as measured by dexamethasone suppression, and (2) between morning cortisol levels and adrenal sensitivity. We did not find links between central drive (metyrapone test) and end of day salivary levels. We confirmed an a priori expectation of limited linkage between regulatory biology and diurnal salivary cortisol measures, beyond those predicted. These data support an emerging focus on measures related to diurnal decline in epidemiological stress work. They raise questions about the biological meaning of other curve components, including morning cortisol levels, and perhaps CAR (Cortisol Awakening Response). If morning cortisol dynamics are linked to stress, more work on adrenal sensitivity in stress adaptation and stress-health links may be warranted.

Sleep and dreaming in the light of reactive and predictive homeostasis

Dreams are often viewed as fascinating but irrelevant mental epihenomena of the sleeping mind with questionable functional relevance. Despite long hours of oneiric activity, and high individual differences in dream recall, dreams are lost into oblivion. Here, we conceptualize dreaming and dream amnesia as inherent aspects of the reactive and predictive homeostatic functions of sleep. Mental activity during sleep conforms to the interplay of restorative processes and future anticipation, and particularly during the second half of the night, it unfolds as a special form of non-constrained, self-referent, and future-oriented cognitive process. Awakening facilitates constrained, goal-directed prospection that competes for shared neural resources with dream production and dream recall, and contributes to dream amnesia. We present the neurophysiological aspects of reactive and predictive homeostasis during sleep, highlighting the putative role of cortisol in predictive homeostasis and forgetting dreams. The theoretical and methodological aspects of our proposal are discussed in relation to the study of dreaming, dream recall, and sleep-related cognitive processes.

Sleeping with time in mind? A literature review and a proposal for a screening questionnaire on self-awakening

Some people report being able to spontaneously "time" the end of their sleep. This ability to self-awaken challenges the idea of sleep as a passive cognitive state. Yet, current evidence on this phenomenon is limited, partly because of the varied definitions of self-awakening and experimental approaches used to study it. Here, we provide a review of the literature on self-awakening. Our aim is to i) contextualise the phenomenon, ii) propose an operating definition, and iii) summarise the scientific approaches used so far. The literature review identified 17 studies on self-awakening. Most of them adopted an objective sleep evaluation (76%), targeted nocturnal sleep (76%), and used a single criterion to define the success of awakening (82%); for most studies, this corresponded to awakening occurring in a time window of 30 minutes around the expected awakening time. Out of 715 total participants, 125 (17%) reported to be self-awakeners, with an average age of 23.24 years and a slight predominance of males compared to females. These results reveal self-awakening as a relatively rare phenomenon. To facilitate the study of self-awakening, and based on the results of the literature review, we propose a quick paper-and-pencil screening questionnaire for self-awakeners and provide an initial validation for it. Taken together, the combined results of the literature review and the proposed questionnaire help in characterising a theoretical framework for self-awakenings, while providing a useful tool and empirical suggestions for future experimental studies, which should ideally employ objective measurements.

Effects of using a snooze alarm on sleep inertia after morning awakening

BACKGROUND

Many people use the snooze function of digital alarm clocks for morning awakening, but the effects of a snooze alarm on waking are unclear. We examined the effects of a snooze alarm on sleep inertia, which is a transitional state characterized by reduced arousal and impaired cognitive and behavioral performance immediately upon awakening.

METHODS

In study 1, healthy Japanese university students responded to a sleep survey during a psychology class (study 1), and we collected 293 valid responses. In study 2, we compared a separate sample of university students (n = 10) for the effects of using or not using a snooze alarm on sleep inertia immediately after awakening from normal nocturnal sleep in a sleep laboratory.

RESULTS

Of 293 valid respondents in study 1, 251 often used a tool to wake up in the morning (85.7%). Moreover, 70.5% reported often using the snooze function of their mobile phones, mainly to reduce anxiety about oversleeping. Study 2 indicated no differences in the sleep quality or quantity before awakening with or without the snooze alarm, except in the last 20 min. However, during the last 20 min of sleep with snooze alarm, the snooze alarm prolonged waking and stage N1 sleep. Stage N1 sleep is non-rapid eye movement sleep that is primarily defined as a drowsy state. Furthermore, Global Vigor values were enhanced after awakening compared to pre-sleep in the no-snooze condition.

CONCLUSIONS

Using a snooze alarm prolongs sleep inertia compared to a single alarm, possibly because snooze alarms induce repeated forced awakenings.

The circadian system modulates the cortisol awakening response in humans

Background

In humans, circulating cortisol usually peaks 30–60 min after awakening from nocturnal sleep, this is commonly referred to as the cortisol awakening response (CAR). We examined the extent to which the CAR is influenced by the circadian system, independent of behaviors including sleep.

Materials and methods

We examined the CAR in 34 adults (20 female) using two complementary multiday in-laboratory circadian protocols performed in dim light, throughout which behavioral factors were uniformly distributed across the 24-hour circadian cycle. Protocol 1 consisted of 10 identical consecutive 5-hour 20-minute sleep/wake cycles, and protocol 2 consisted of 5 identical consecutive 18-hour sleep/wake cycles. Salivary melatonin was used as the circadian phase marker (0° = dim light melatonin onset). During each sleep/wake cycle, salivary cortisol was measured upon scheduled awakening and 50-minutes later, with the change in cortisol defined as the CAR. Cosinor analyses were used to detect any significant circadian rhythmicity in the CAR. In secondary analyses, we adjusted the models for time awake before lights on, total sleep time, percent of rapid eye movement (REM) sleep, and percent of non-rapid eye movement (NREM) sleep.

Results

Both protocols revealed a similar circadian rhythm in the CAR, with peaks occurring at a circadian phase corresponding to 3:40–3:45 a.m., with no detectable CAR during the circadian phases corresponding to the afternoon. In addition to the sinusoidal component of the circadian rhythm, total sleep time was also associated with the CAR for protocol 1. The percent of sleep spent in REM or NREM sleep were not associated with the CAR in either protocol.

Conclusion

Our results show that the CAR exhibits a robust circadian rhythm that persists even after adjusting for prior sleep. Presuming that the CAR optimizes physiological responses to the anticipated stressors related to awakening, these findings may have implications for shift workers who wake up at unusual circadian phases. A blunted CAR in shift workers upon awakening in the evening may result in diminished responses to stressors.

Serum Cortisol, Nesfatin-1, and IL-1β: Potential Diagnostic Biomarkers in Elderly Patients with Treatment-Resistant Depression

Aim

Treatment-resistant depression (TRD) affects approximately 30% of patients with major depressive disorder (MDD), especially elderly patients. As individuals with TRD are at an increased risk of committing suicide and pose a higher risk of relapse, early diagnostic biomarkers of TRD and a better understanding of the resistance mechanism are highly needed. This study aimed to determine whether serum cortisol, nesfatin-1, and pro-inflammatory cytokines can be used as biomarkers for the diagnosis of elderly patients with TRD.

Methods

Thirty elderly patients with TRD were selected as the TRD group. Thirty elderly patients with MDD who were effectively treated with conventional antidepressants were selected as the non-TRD group. The baseline levels of serum cortisol, nesfatin-1, and pro-inflammatory cytokines were measured and compared, and their diagnostic values were evaluated using the receiver operating characteristic (ROC) curve method for discriminating patients with TRD from those without TRD.

Results

Serum cortisol, C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) levels were significantly higher in the non-TRD and TRD groups than in the control group. Moreover, serum cortisol, CRP, TNF-α, and IL-6 levels in the TRD group were significantly lower than those in the non-TRD group. Furthermore, serum nesfatin-1 levels in the non-TRD group were significantly lower than those in the control and TRD groups, while the serum IL-1β levels in the non-TRD group were significantly higher than those in the control and TRD groups. Additionally, an ROC analysis revealed an area under the curve (AUC) of 0.929 for the combination of nesfatin-1 and IL-1β and an AUC of 0.956 for the combination of cortisol, nesfatin-1, and IL-1β in discriminating elderly patients with TRD from those without non-TRD.

Conclusion

Serum cortisol, nesfatin-1, and IL-1β may be potential diagnostic biomarkers for discriminating elderly patients with TRD from those without TRD.

Stress dynamically reduces sleep depth: temporal proximity to the stressor is crucial

The anticipation of a future stressor can increase worry and cognitive arousal and has a detrimental effect on sleep. Similarly, experiencing a stressful event directly before sleep increases physiological and cognitive arousal and impairs subsequent sleep. However, the effects of post- vs. pre-sleep stress on sleep and their temporal dynamics have never been directly compared. Here, we examined the effect of an anticipated psychosocial stressor on sleep and arousal in a 90-min daytime nap, in 33 healthy female participants compared to an anticipated within-subject relaxation task. We compared the results to an additional group (n = 34) performing the same tasks directly before sleep. Anticipating stress after sleep reduced slow-wave activity/beta power ratio, slow-wave sleep, sleep spindles, and slow-wave parameters, in particular during late sleep, without a concomitant increase in physiological arousal. In contrast, pre-sleep psychosocial stress deteriorated the same parameters during early sleep with a concomitant increase in physiological arousal. Our results show that presleep cognitions directly affect sleep in temporal proximity to the stressor. While physiological arousal mediates the effects of presleep stress on early sleep, we suggest that effects during late sleep originate from a repeated reactivation of mental concepts associated with the stressful event during sleep.

From work stress to disease: A computational model

In modern society, work stress is highly prevalent. Problematically, work stress can cause disease. To help understand the causal relationship between work stress and disease, we present a computational model of this relationship. That is, drawing from allostatic load theory, we captured the link between work stress and disease in a set of mathematical formulas. With simulation studies, we then examined our model’s ability to reproduce key findings from previous empirical research. Specifically, results from Study 1 suggested that our model could accurately reproduce established findings on daily fluctuations in cortisol levels (both on the group level and the individual level). Results from Study 2 suggested that our model could accurately reproduce established findings on the relationship between work stress and cardiovascular disease. Finally, results from Study 3 yielded new predictions about the relationship between workweek configurations (i.e., how working hours are distributed over days) and the subsequent development of disease. Together, our studies suggest a new, computational approach to studying the causal link between work stress and disease. We suggest that this approach is fruitful, as it aids the development of falsifiable theory, and as it opens up new ways of generating predictions about why and when work stress is (un)healthy.

Sleep and psychological characteristics in habitual self-awakeners and forced awakeners

Previous studies described the modifications of physiological and behavioural variables associated with self-awakening, while only few studies assessed subjective sleep quality and psychological characteristics in habitual self-awakeners. Here we investigated self-reported sleep habits and features, as well as psychological variables of habitual self-awakeners and forced-awakeners, with special regard to subjective sleep quality, personality characteristics, anxiety and depression symptoms. In our sample, the prevalence of habitual self-awakeners was 15.1%. Compared to forced-awakeners, habitual self-awakeners showed more regular sleep/wake schedules and were more frequently morning types. Moreover, habitual self-awakeners referred to be more satisfied about their sleep, to wake up more easily in the morning, to need less time to get out of bed and to feel more refreshed upon awakening than forced-awakeners. We also observed an association between the habit of self-awakening and the "ability" to set the awakening to an unusual time. Concerning psychological features, habitual self-awakeners showed higher scores in Conscientiousness and Openness and lower scores in Extraversion compared to forced-awakeners, whereas no differences between groups emerged for anxiety and depression levels. In conclusion, our findings point to an association between the habit of self-awakening and good subjective sleep quality. In this perspective, future research should objectively test in detail the effects of the self-awakening habit on sleep structure and organization, taking into account also microstructural sleep features.

Time-lag of urinary and salivary cortisol response after a psychological stressor in bonobos (Pan paniscus)

Cortisol is often measured as a marker for stress. Therefore, a profound validation of the time-lag between the stressor and the increase and peak in cortisol levels is needed. No study measured both the urinary and salivary cortisol time-lag after a psychological stressor. In this study, we used a frequent sampling study design to (1) describe the urinary and salivary cortisol pattern during a control day; and (2) characterize the induced excretion pattern of urinary and salivary cortisol after a psychological stressor in six zoo-housed bonobos. Liquid chromatography-tandem mass spectrometry was used to analyze 71 urine and 162 saliva samples collected on a control and a test day. We found that the time-lag between the stressor and the maximal cortisol concentration was similar in urine and saliva (160 min after the stressor). However, salivary cortisol after the stressor did show a faster and steeper increase than urinary cortisol. We also show inter-individual variation in the baseline and stress levels of cortisol, which should be considered in future cortisol studies. Our research highlights the importance of validation studies to confirm relevant sampling windows for cortisol sampling in order to obtain biologically meaningful results.

Sleep, Cognition and Cortisol in Addison's Disease: A Mechanistic Relationship

Sleep is a critical biological process, essential for cognitive well-being. Neuroscientific literature suggests there are mechanistic relations between sleep disruption and memory deficits, and that varying concentrations of cortisol may play an important role in mediating those relations. Patients with Addison's disease (AD) experience consistent and predictable periods of sub- and supra-physiological cortisol concentrations due to lifelong glucocorticoid replacement therapy, and they frequently report disrupted sleep and impaired memory. These disruptions and impairments may be related to the failure of replacement regimens to restore a normal circadian rhythm of cortisol secretion. Available data provides support for existing theoretical frameworks which postulate that in AD and other neuroendocrine, neurological, or psychiatric disorders, disrupted sleep is an important biological mechanism that underlies, at least partially, the memory impairments that patients frequently report experiencing. Given the literature linking sleep disruption and cognitive impairment in AD, future initiatives should aim to improve patients' cognitive performance (and, indeed, their overall quality of life) by prioritizing and optimizing sleep. This review summarizes the literature on sleep and cognition in AD, and the role that cortisol concentrations play in the relationship between the two.

The Jaw Epidemic: Recognition, Origins, Cures, and Prevention

Contemporary humans are living very different lives from those of their ancestors, and some of the changes have had serious consequences for health. Multiple chronic "diseases of civilization," such as cardiovascular problems, cancers, ADHD, and dementias are prevalent, increasing morbidity rates. Stress, including the disruption of traditional sleep patterns by modern lifestyles, plays a prominent role in the etiology of these diseases, including obstructive sleep apnea. Surprisingly, jaw shrinkage since the agricultural revolution, leading to an epidemic of crooked teeth, a lack of adequate space for the last molars (wisdom teeth), and constricted airways, is a major cause of sleep-related stress. Despite claims that the cause of this jaw epidemic is somehow genetic, the speed with which human jaws have changed, especially in the last few centuries, is much too fast to be evolutionary. Correlation in time and space strongly suggests the symptoms are phenotypic responses to a vast natural experiment-rapid and dramatic modifications of human physical and cultural environments. The agricultural and industrial revolutions have produced smaller jaws and less-toned muscles of the face and oropharynx, which contribute to the serious health problems mentioned above. The mechanism of change, research and clinical trials suggest, lies in orofacial posture, the way people now hold their jaws when not voluntarily moving them in speaking or eating and especially when sleeping. The critical resting oral posture has been disrupted in societies no longer hunting and gathering. Virtually all aspects of how modern people function and rest are radically different from those of our ancestors. We also briefly discuss treatment of jaw symptoms and possible clinical cures for individuals, as well as changes in society that might lead to better care and, ultimately, prevention.

Assessment of feasibility and outcomes of a salivary cortisol collection protocol in five American Indian communities

We evaluated the feasibility and outcomes of administering a naturalistic saliva collection procedure and assessment in American Indian (Indigenous) communities. We focus on Indigenous adults living with type 2 diabetes given the "epidemic" of the disease disproportionately impacting many tribal groups. Data are from community-based participatory research (CBPR) involving 5 tribal communities. Participants were randomly selected from tribal clinic records. The sample includes 188 adults living with type 2 diabetes (56% female; age range = 18-77 years; M age = 46.3 years). Participants provided a total of 748 saliva samples, representing 4 samples/participant on a single day with instructions for collection at 4 time points: upon waking, 1 h after waking, 2 h after waking, and at 8 PM. Saliva sample times were recorded by participants on paper and electronically via placement in a Medication Event Monitoring System (MEMS®) bottle. Overall, 67% of samples were completed within 10 min of protocol instructions and 91% of participants provided at least one useable sample (79% provided four useable samples). Noncompliance, behavioral and environmental factors were not robustly associated with deviations in observed cortisol indices. Results suggest that home-based, community interviewer-involved protocols yields valid data with high compliance. The success of this study was facilitated by exemplary efforts of tribal community-based interviewers and our overall CBPR approach.Lay summaryAuthentic efforts for tribal community partnerships in research are critical to successfully implementing biological assessments with American Indians given legacies of research misconduct and mistrustOur Community-Based Participatory Research with 5 tribes yielded high participant compliance to a home-based salivary cortisol collection protocolLack of compliance to salivary cortisol protocol and medication usage were not consistently associated with observed cortisol indices.

Diurnal variation of salivary cortisol in captive African elephants (Loxodonta africana) under routine management conditions and in relation to a translocation event

The present study assessed the diurnal variation in salivary cortisol in captive African elephants during routine management (baseline) and in relation to a potential stressor (translocation) to evaluate to what extent acute stress may affect diurnal cortisol patterns. Under baseline conditions, we collected morning and afternoon saliva samples of 10 animals (three zoos) on different days in two study periods (n = 3-10 per animal, daytime and period). Under stress conditions, we sampled the transported cow (newcomer) and the two cows of the destination zoo before and after the transport in the morning and afternoon (n = 3-9 per animal, daytime and transport phase), as well as after the first introduction of the newcomer to the bull (n = 1 per animal). Cortisol was measured in unextracted samples by enzyme immunoassay. Under baseline conditions, we observed the expected diurnal variation with higher cortisol levels in the morning than in the afternoon. Under stress conditions, neither a significant difference between pre- and posttransport, nor between morning and afternoon levels was found. The percentage difference between morning and afternoon cortisol after the transport, however, was remarkably lower than before the transport in the newcomer potentially indicating a stress response to familiarization. Saliva samples taken immediately after the introduction of the newcomer to the bull revealed a marked cortisol increase. Our findings indicate that stressors may disturb the diurnal cortisol rhythm. Furthermore, provided that samples can be collected promptly, salivary cortisol is a useful minimally invasive measure of physiological stress in the African elephant.

Characterization of Cortisol Dysregulation in Fibromyalgia and Chronic Fatigue Syndromes: A State-Space Approach

OBJECTIVE

Fibromyalgia syndrome (FMS) and chronic fatigue syndrome (CFS) are complicated medical disorders, with little known etiologies. The purpose of this research is to characterize FMS and CFS by studying the variations in cortisol secretion patterns, timings, amplitudes, the number of underlying pulses, as well as infusion and clearance rates of cortisol.

METHODS

Using a physiological state-space model with plausible constraints, we estimate the hormonal secretory events and the physiological system parameters (i.e., infusion and clearance rates).

RESULTS

Our results show that the clearance rate of cortisol is lower in FMS patients as compared to their matched healthy individuals based on a simplified cortisol secretion model. Moreover, the number, magnitude, and energy of hormonal secretory events are lower in FMS patients. During early morning hours, the magnitude and energy of the hormonal secretory events are higher in CFS patients.

CONCLUSION

Due to lower cortisol clearance rate, there is a higher accumulation of cortisol in FMS patients as compared to their matched healthy subjects. As the FMS patient accumulates higher cortisol residues, internal inhibitory feedback regulates the hormonal secretory events. Therefore, the FMS patients show a lower number, magnitude, and energy of hormonal secretory events. Though CFS patients have the same number of secretory events, they secrete lower quantities during early morning hours. When we compare the results for CFS patients against FMS patients, we observe different cortisol alteration patterns.

SIGNIFICANCE

Characterizing CFS and FMS based on the cortisol alteration will help us to develop novel methods for treating these disorders.

Pavlovian Conditioning of Immunological and Neuroendocrine Functions

The phenomenon of behaviorally conditioned immunological and neuroendocrine functions has been investigated for the past 100 yr. The observation that associative learning processes can modify peripheral immune functions was first reported and investigated by Ivan Petrovic Pavlov and his co-workers. Their work later fell into oblivion, also because so little was known about the immune system’s function and even less about the underlying mechanisms of how learning, a central nervous system activity, could affect peripheral immune responses. With the employment of a taste-avoidance paradigm in rats, this phenomenon was rediscovered 45 yr ago as one of the most fascinating examples of the reciprocal functional interaction between behavior, the brain, and peripheral immune functions, and it established psychoneuroimmunology as a new research field. Relying on growing knowledge about efferent and afferent communication pathways between the brain, neuroendocrine system, primary and secondary immune organs, and immunocompetent cells, experimental animal studies demonstrate that cellular and humoral immune and neuroendocrine functions can be modulated via associative learning protocols. These (from the classical perspective) learned immune responses are clinically relevant, since they affect the development and progression of immune-related diseases and, more importantly, are also inducible in humans. The increased knowledge about the neuropsychological machinery steering learning and memory processes together with recent insight into the mechanisms mediating placebo responses provide fascinating perspectives to exploit these learned immune and neuroendocrine responses as supportive therapies, the aim being to reduce the amount of medication required, diminishing unwanted drug side effects while maximizing the therapeutic effect for the patient’s benefit.

Healthy Sleepers Can Worsen Their Sleep by Wanting to Do so: The Effects of Intention on Objective and Subjective Sleep Parameters

PURPOSE

Sleep is regulated by homeostatic and circadian factors. In addition, psychological factors have a strong modulatory impact on our sleep, but the exact underlying mechanisms are still largely unknown. Here, we examined the role of intentions on subjective and objective sleep parameters. Young healthy sleepers were instructed to voluntarily either worsen or improve their sleep. We predicted that participants would be capable of worsening, but not improving, their sleep compared to a regular sleep condition. In addition, we predicted that the instruction to alter sleep would lead to a higher discrepancy between subjective and objective sleep variables.

PARTICIPANTS AND METHODS

Twenty-two healthy students participated in one adaptation and three experimental nights. Polysomnography and subjective sleep parameters were measured during all four nights. Participants were instructed to sleep regularly ("neutral"), better ("good") or worse ("bad") than normal, in a counterbalanced order.

RESULTS

The instruction to sleep "bad" increased objective sleep onset latency and the number of awakings during the night. The effects were stronger on subjective sleep variables, resulting in a higher sleep misperception in the "bad" condition as compared to the other two conditions. The instruction to sleep "good" did not improve sleep nor did it affect sleep misperception.

CONCLUSION

We conclude that intention is sufficient to impair (but not improve) subjective and objective sleep quality and to increase sleep misperception in healthy young sleepers. Our results have important implications for the understanding of the impact of psychological factors on our sleep.

Habitual Sleep, Social Jetlag, and Reaction Time in Youths With Delayed Sleep-Wake Phase Disorder. A Case-Control Study

The aim of this study was to explore habitual sleep, social jetlag, and day-to-day variations in sleep (measured as intra-individual standard deviation, ISD) in youths with delayed sleep-wake phase disorder (DSWPD), compared to healthy controls. We also aimed to investigate time of day effects in performance. The sample comprised 40 youths with DSWPD (70.0% female, mean age 20.7 ± 3.1 years) and 21 healthy controls (71.4% female, mean age 21.2 ± 2.2 years). Subjective and objective sleep were measured over 7 days on a habitual sleep schedule by sleep diary and actigraphy recordings. Performance was tested twice with a 12-h interval (22:00 in the evening and 10:00 the following morning) using a simple, 10-min sustained reaction time test (RTT). The results showed later sleep timing in the DSWPD group compared to the controls, but sleep duration, social jetlag, and ISD in sleep timing did not differ between the groups. Still, participants with DSWPD reported longer sleep onset latency (SOL) and poorer sleep efficiency (SE), sleep quality, and daytime functioning, as well as larger ISD in SOL, sleep duration, and SE. The groups had similar evening performances on the RTT, but the DSWPD group performed poorer (slower with more lapses) than the controls in the morning. The poor morning performance in the DSWPD group likely reflects the combined impact of sleep curtailment and circadian variations in performance (synchrony effect), and importantly illustrates the challenges individuals with DSWPD face when trying to adhere to early morning obligations.

Efficacy and safety of oral SOCG in treatment of major depressive disorder: A protocol for a phase II, randomized, double-blind, placebo controlled, parallel-groups, dose finding exploratory study

INTRODUCTION

Major depressive disorder (MDD) is a common condition worldwide, and leads to degradation in quality of life and large socioeconomic costs. There has been increasing demand for new therapies with fewer side effects. SOCG (SOCG tablet) is a modified prescription of So-ochim-tang, which is widely used in Traditional Korean Medicine to treat MDD. We aim to evaluate the efficacy of SOCG in treating MDD, and identify the optimum dose.

DESIGN

The protocol we are following is that of a Phase II clinical trial with a randomized, double blinded, placebo controlled, and parallel design. One hundred forty-eight participants will be randomly divided into 4 groups and treated for 8 weeks.

OUTCOME MEASURES

The primary outcome will be the score in the Korean Version of the Hamilton Depression Rating Scale. Scores in the Korean version of the Beck Depression Inventory-II Korean Symptom Check List-95 (KSCL-95), State Trait Anxiety Inventory-Korean version, State- Trait Anger Expression Inventory- Korean version (STAXI-K), Insomnia Severity Index (ISI), and the EuroQol-5 Dimension (EQ-5D) will be considered as secondary outcomes.

DISCUSSION AND CONCLUSIONS

Demonstration of human safety and efficacy of SOCG in the present trial and identification of the appropriate dose will justify a New Drug Application and a phase III clinical trial. Further, we expect that this new antidepressant will be able to increase cure rates, and alleviate the burden of medical expenses.

TRIAL REGISTRATION NUMBER

Clinical Research Information Service, Republic of Korea (KCT0002763).

Timing Modulates the Effect of Sleep Loss on Glucose Homeostasis

CONTEXT

Chronobiological factors may modulate the impact of sleep loss on glucose homeostasis. However, these interactions have not been systematically assessed in humans.

OBJECTIVE

To assess the effect of sleep loss during the late vs early night on glucose homeostasis.

DESIGN

Fifteen normal-weight men participated in three conditions of a randomized, balanced crossover study comprising two conditions with shortened sleep (i.e., 4 hours of sleep during the first or the second half of the night) and a control condition with 8 hours of sleep. Glucose, insulin, cortisol, and glucagon were measured. Insulin sensitivity and secretion were assessed with a Botnia clamp.

RESULTS

Compared with regular sleep duration, sleep loss reduced insulin sensitivity (M-value; P = 0.031) irrespective of early- or late-night timing (P = 0.691). The disposition index (i.e., the β-cell response adjusted for insulin sensitivity) also tended to be impaired by short sleep (P = 0.056) but not by sleep timing (P = 0.543). In contrast, sleep loss in the second half but not the first half of the night induced reductions in morning glucagon and cortisol levels (P < 0.031) followed by a transient increase in cortisol (P < 0.044).

CONCLUSIONS

Although sleep deprivation acutely reduced insulin sensitivity irrespective of its nocturnal timing, sleep loss in the early morning compromised α-cell and hypothalamic-pituitary-adrenal axis activity to a greater extent than sleep loss in the first half of the night. This pattern suggests that the timing of sleep restriction can partly potentiate its deleterious metabolic effects.

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.

Altered ultradian cortisol rhythmicity as a potential neurobiologic substrate for chronic insomnia

Chronic insomnia is highly prevalent and associated with significant morbidity (i.e., confers risk for multiple psychiatric and medical disorders, such as depression and hypertension). Therefore, it is essential to identify factors that perpetuate this disorder. One candidate factor in the neurobiology of chronic insomnia is hypothalamic-pituitary-adrenal-axis dysregulation, and in particular, alterations in circadian cortisol rhythmicity. Cortisol secretory patterns, however, fluctuate with both a circadian and an ultradian rhythm (i.e., pulses every 60-120 min). Ultradian cortisol pulses are thought to be involved in the maintenance of wakefulness during the day and their relative absence at night may allow for the consolidation of sleep and/or shorter nocturnal awakenings. It is possible that the wakefulness that occurs in chronic insomnia may be associated with the aberrant occurrence of cortisol pulses at night. While cortisol pulses naturally occur with transient awakenings, it may also be the case that cortisol pulsatility becomes a conditioned phenomenon that predisposes one to awaken and/or experience prolonged nocturnal awakenings. The current review summarizes the literature on cortisol rhythmicity in subjects with chronic insomnia, and proffers the suggestion that it may be abnormalities in the ultradian rather than circadian cortisol that is associated with the pathophysiology of insomnia.

Will daytime occupational noise exposures induce nighttime sleep disturbance?

BACKGROUND

Nighttime environmental noise affects sleep quality. However, the effects of daytime occupational noise remain unclear.

METHODS

A quasi-experiment of 48 participants who had been employed for at least six months in two hospital cafeterias. The participants were randomly designated to be assessed on high- and low-noise workdays for 8 h or low- and high-noise workdays, separated by a washout period of 14 days. Subsequently, pure tone audiometry, autonomic nervous system (ANS) function tests, serum cortisol tests, and polysomnography were conducted.

RESULTS

For the 40 participants in the study, the 8-h time-weighted average of personal noise exposed on high- and low-noise workdays was 76.8 dBA (standard deviation, SD: 6.2) and 61.0 dBA (SD: 7.1), respectively. Participants with higher personal noise exposure during the day were found to have a lower percentage of slow wave sleep (percent change of mean value: -1.287%; 95% CI: -2.602%, -0.037%) and lower sleep efficiency (-0.267%; 95% CI: -0.525%, -0.008%). In addition, after work, personal noise exposure was revealed to be related to increased serum cortisol levels (1.698%; 95% CI: 0.887%, 2.528%), and sympathetic activity as measured by low frequency/high frequency (3.000%; 95% CI: 1.294%, 4.706%) and blood pressures by cold pressor test (systolic: 5.163%; 95% CI: 2.780%, 7.537%) (diastolic: 3.109%; 95% CI: 1.604%, 4.614%).

CONCLUSIONS

Daytime occupational noise exposure had sustained effects on nighttime sleep quality, specifically on slow wave sleep and sleep efficiency. These disturbances could be partially explained by post-shift elevated cortisol and ANS activity. The psychosocial and metabolic consequences of poorer sleep quality induced by occupational noise exposure warrant further investigation.

Mechanisms underlying the association between insomnia, anxiety, and depression in adolescence: Implications for behavioral sleep interventions

There is robust evidence of an association between insomnia, anxiety, and depression in adolescence. The aim of this review is to describe and synthesize potential mechanisms underlying this association and explore implications for the design of adolescent behavioral sleep interventions. Specifically, we examine whether insomnia symptoms are a mechanism for the development of internalizing symptoms in adolescence and whether sleep interventions are an effective treatment for both insomnia and internalizing symptoms in adolescence because they target the shared mechanisms underlying these disorders. Research using different methodologies points to the role of sequential, parallel, and interacting mechanisms. In this paper, we review a wide range of relevant biological (i.e., polymorphisms and dysregulation in serotonin, dopamine, and circadian clock genes; alterations in corticolimbic and mesolimbic brain circuits; cortisol reactivity to stress; inflammatory cytokine dysregulation; biased memory consolidation; changes in sleep architecture), psychological (i.e., cognitive inflexibility, interpretational biases, judgment biases, negative attribution styles, worry, rumination, biased attention to threat, dysfunctional beliefs and attitudes about sleep, misperception of sleep deficit), and social mechanisms (i.e., reduced and impaired social interactions, unhelpful parenting behaviors, family stress) and propose an integrative multilevel model of how these phenomena may interact to increase vulnerability to both insomnia and internalizing disorders. Several 'biopsychosocial' mechanisms hold promise as viable treatment targets for adolescent behavioral sleep interventions, which may reduce both insomnia and internalizing symptoms.

Morning blood pressure surge: pathophysiology, clinical relevance and therapeutic aspects

Morning hours are the period of the day characterized by the highest incidence of major cardiovascular events including myocardial infarction, sudden death or stroke. They are also characterized by important neurohormonal changes, in particular, the activation of sympathetic nervous system which usually leads to a rapid increase in blood pressure (BP), known as morning blood pressure surge (MBPS). It was hypothesized that excessive MBPS may be causally involved in the pathogenesis of cardiovascular events occurring in the morning by inducing hemodynamic stress. A number of studies support an independent relationship of MBPS with organ damage, cerebrovascular complications and mortality, although some heterogeneity exists in the available evidence. This may be due to ethnic differences, methodological issues and the confounding relationship of MBPS with other features of 24-hour BP profile, such as nocturnal dipping or BP variability. Several studies are also available dealing with treatment effects on MBPS and indicating the importance of long-acting antihypertensive drugs in this regard. This paper provides an overview of pathophysiologic, methodological, prognostic and therapeutic aspects related to MBPS.

Analysis of variability in length of sleep state bouts reveals memory-free sleep subcomponents consistent among primary insomnia patients

The statistical distributions of bout lengths for the different (macro) sleep states (wake, N1, N2, N3, and REM sleep) are essential to understanding whether any memory-free subcomponent ("micro state") is involved in the organization of sleep. Micro state detection can be prevented by the fusion of data including various sources of variability, in particular by the differences in sleep architecture between individuals, along sleep time (or nighttime), or between different nights. In this analysis, a mathematical model of sleep was adopted to disentangle these features and advance the understanding of the dynamics and mechanisms of sleep and its states. The analysis involved 116 primary insomnia patients taking placebo before going to bed and undergoing polysomnography for one night. The individual sequences of macro sleep states had been previously modeled with a mixed-effect nonhomogeneous modified Markov chain model, from which individual conditional probability distributions for the bout durations were derived in this analysis as functions of sleep time. The probability distributions, affected by neither subject, night-time, nor multiple-night pooling, substantially changed at ¼ and ¾ sleep time, had modified exponential shape, and were best described as the sum of one to four exponentials, depending on the sleep state. The time constants and proportions of bouts contributing to each exponential were similar in the different subjects, changing over sleep time. Variability in bout durations thus indicated the presence of multiple memory-free sleep subcomponents whose mean residence times and access probabilities could be identified and shown to be consistent among the studied subjects. NEW & NOTEWORTHY We present a new methodology for deriving, from polysomnography data, the individual conditional probability for the duration of the bouts of wake, N1, N2, N3, and REM sleep. We evaluated the variability of this probability within and between primary insomnia patients and along sleep time. The multiexponential shapes of the probability distributions within the individuals revealed memory-free mechanisms and sleep subcomponents with consistent features in the studied population.

The cortisol awakening response after sleep deprivation: Is the cortisol awakening response a "response" to awakening or a circadian process?

This study tested whether the cortisol awakening response is dependent on the transition from sleep to awakening, or alternatively, a circadian-driven process that is independent of awakening. A total of 40 participants were randomly assigned to either a total sleep deprivation or a sleep condition. Salivary cortisol was also assessed. Participants in the sleep condition demonstrated a traditional cortisol awakening response, whereas participants in the total sleep deprivation condition showed no increases in morning cortisol. These results are consistent with the notion that if circadian-driven processes are related to the cortisol awakening response, they may only be activated when awakening occurs or is anticipated.

The Cortisol Awakening Response and Depressive Symptomatology: The Moderating Role of Sleep and Gender

The association between depression and the cortisol awakening response (CAR) has been widely examined, yet the results are mixed and factors responsible for such inconsistencies are poorly understood. The current study investigated whether the link between depressive symptomatology and CAR varied as a function of two such factors: sleep and gender. The sample included 58 young adults (30 females; M_age  = 18.7; SD_age  = 0.91). Participants completed the Beck Depression Inventory as well as the Consensus Sleep Diary to assess depressive symptomatology and daily sleep patterns, respectively. Participants also provided four salivary cortisol samples (0, 30, 45 and 60 min after awakening) during two consecutive weekdays. Results demonstrated that greater depressive symptoms were associated with a greater CAR but only when depressive symptoms were linked to a shorter sleep time. In addition, gender significantly moderated the association between depressive symptoms and CAR. While greater depressive symptoms were associated with an elevated CAR among females, they were associated with a blunted CAR among males. These findings provide some insight into potential mechanisms linking depressive symptomatology and CAR, and suggest that future studies examining CAR as a biomarker of depression should account for differences in sleep and gender. Copyright © 2016 John Wiley & Sons, Ltd.

Is physiological glucocorticoid replacement important in children?

Cortisol has a distinct circadian rhythm with low concentrations at night, rising in the early hours of the morning, peaking on waking and declining over the day to low concentrations in the evening. Loss of this circadian rhythm, as seen in jetlag and shift work, is associated with fatigue in the short term and diabetes and obesity in the medium to long term. Patients with adrenal insufficiency on current glucocorticoid replacement with hydrocortisone have unphysiological cortisol concentrations being low on waking and high after each dose of hydrocortisone. Patients with adrenal insufficiency complain of fatigue, a poor quality of life and there is evidence of poor health outcomes including obesity potentially related to glucocorticoid replacement. New technologies are being developed that deliver more physiological glucocorticoid replacement including hydrocortisone by subcutaneous pump, Plenadren, a once-daily modified-release hydrocortisone and Chronocort, a delayed and sustained absorption hydrocortisone formulation that replicates the overnight profile of cortisol. In this review, we summarise the evidence regarding physiological glucocorticoid replacement with a focus on relevance to paediatrics.

Effects of Self-Awakening on Sleep Structure of a Daytime Short Nap and on Subsequent Arousal Levels

To investigate the effects of self-awakening on sleep structure and daytime arousal after a short nap, a within-subjects comparison was made of participants in self-awakening and forced-awakening conditions. In the self-awakening condition, participants were instructed to wake up by themselves 15 min. after the experimenter turned the lights off. In the forced-awakening condition, the experimenter awakened them 20 min. after the lights were turned off. To control the maximum sleep time for the two conditions, we used different instructions in each condition. Participants were 10 healthy college students. Their physiological arousal and subjective sleepiness were evaluated using the P300 amplitude of the auditory event-related potential (ERP) and the visual analog scale previously described by Monk and Kathryn, et al. For evaluating sleep structure during the nap, Hori's 1994 hypnagogic EEG stages were used. P300 amplitude was significantly lower, and subjective sleepiness was significantly higher after forced-awakening than self-awakening, indicating that arousal was higher after self-awakening. The EEGs during napping in the forced-awakening condition indicated deeper sleep. Given this deeper sleep, severe sleep inertia occurred after the forced-awakening condition. In conclusion, it appeared a short nap with self-awakening was more effective in reducing a post-lunch dip than one with forced-awakening.

Is afternoon cortisol more reliable than waking cortisol in association studies of children with an ASD?

Salivary cortisol may be used as a biomarker of stress and anxiety in children with an Autism Spectrum Disorder (ASD) and is particularly valuable in studies of the association between stress-related cortisol concentrations and other factors such as comorbid disorders or aspects of the ASD phenotype. Although protocols for the collection of cortisol shortly after waking are often based on the assumption of the presence of a diurnal rhythm in cortisol, that rhythm may not be as reliable in children with an ASD as in non-ASD children. Alternatively, collecting cortisol during the afternoon may represent a more reliable procedure with less inter-participant variability.

Assessing the daily stability of the cortisol awakening response in a controlled environment

Background

Levels of cortisol, the end product of the hypothalamic-pituitary-adrenal (HPA) axis, display a sharp increase immediately upon awakening, known as the cortisol awakening response (CAR). The daily stability of the CAR is potentially influenced by a range of methodological factors, including light exposure, participant adherence, sleep duration and nocturnal awakenings, making inferences about variations in the CAR difficult. The aim of the present study was to determine the daily stability of multiple measurement indices of the CAR in a highly-controlled sleep laboratory environment. A secondary aim was to examine the association between objective sleep continuity and sleep architecture, and the CAR.

Methods

The CAR was assessed in 15 healthy normal sleepers (seven male, eight female, M_age = 23.67 ± 3.49 years) on three consecutive weekday mornings. Sleep was measured objectively using polysomnography. Saliva samples were obtained at awakening, +15, +30, +45 and +60 min, from which multiple CAR measurement indices were derived: cortisol levels at each time point, awakening cortisol levels, the mean increase in cortisol levels (MnInc) and total cortisol secretion during the measurement period. Morning 2 and Morning 3 awakening cortisol levels, MnInc and total cortisol secretion were compared and the relationship between Night 1 and Night 2 objective measures of sleep continuity and architecture, and the subsequent CAR, was also assessed.

Results

There were no differences in cortisol levels at each time point, or total cortisol secretion during the CAR period, between Morning 2 and Morning 3. Awakening cortisol levels were lower, and the MnInc was higher, on Morning 3. Morning 2 and Morning 3 awakening levels (r = 0.77) and total cortisol secretion (r = 0.82), but not the magnitude of increase, were positively associated.

Conclusions

The stability of the CAR profile and total cortisol secretion, but not awakening cortisol levels or the magnitude of increase, was demonstrated across two consecutive mornings of measurement in a highly-controlled environment. Awakening cortisol levels, and the magnitude of increase, may be sensitive to differences in daily activities.

Electronic supplementary material

The online version of this article (doi:10.1186/s40359-016-0107-6) contains supplementary material, which is available to authorized users.

A time to be stressed? Time perspectives and cortisol dynamics among healthy adults

Perceptions of past, present, and future events may be related to stress pathophysiology. We assessed whether Time Perspective (TP) is associated with cortisol dynamics among healthy adults (N=61, Ages=18-35, M=22.9, SD=4.1) exposed to the Trier Social Stress Test (TSST). TP was measured according to two profiles: maladaptive Deviation from Balanced TP (DBTP) and adaptive Deviation from Negative TP (DNTP). Eight salivary cortisol samples were analyzed using area under the curve with respect to ground (AUCg) and to increase (AUCi). Statistic analyses involved partial correlations controlling for depressive symptoms. Results for both sexes showed that higher DBTP scores were associated with lower cortisol AUCg scores, while higher DNTP scores were associated with higher cortisol AUCg scores. These novel findings suggest that maladaptive TP profiles influence hypocortisolism, whereas adaptive TP profiles influence hypercortisolism. Thus, TP profiles may impact conditions characterized by altered cortisol concentrations.

Circadian cortisol and fatigue severity in relapsing-remitting multiple sclerosis

Cortisol is a key regulator of the immune system, energy metabolism, and stress, yet its relevance to fatigue experienced by people with relapsing-remitting multiple sclerosis (RRMS) remains uncertain. We examined cortisol secretory activity in RRMS and its association with fatigue severity between-individuals and within-individuals (day-to-day) using a case-control ecological momentary assessment design. While undergoing usual daily routines, 38 people with RRMS and 38 healthy control participants provided saliva samples at strategic time-points over 4 consecutive weekdays to measure the cortisol awakening response (CAR; 0, 30, and 45 min after awakening) and the diurnal cortisol slope (DCS; 6 quasi-random samples provided between 1000 h and 2000 h). Recalled fatigue was measured at baseline, and daily fatigue was measured as the mean average of momentary fatigue ratings provided alongside each DCS sample. Multilevel modeling found CAR output was greater in RRMS than controls, and recalled fatigue in RRMS was associated with both lower waking cortisol level and larger awakening response. Day-to-day, the CAR was not associated with same-day fatigue levels in RRMS. Cortisol appears to have a role in fatigue experienced in RRMS, but whether it is a causal factor remains unclear.

Prospective evaluation of associations between prenatal cortisol and adulthood coronary heart disease risk: the New England family study

OBJECTIVE

Increasing evidence suggests that early life factors may influence coronary heart disease (CHD) risk; however, little is known about the contributions of prenatal cortisol. Objectives were to prospectively assess the associations of maternal cortisol levels during pregnancy with offspring's 10-year CHD risk during middle age.

METHODS

Participants were 262 mother-offspring dyads from the New England Family Study. Maternal free cortisol was assessed in third-trimester maternal serum samples. Ten-year CHD risk was calculated in offspring at a mean age of 42 years, using the validated Framingham risk algorithm incorporating diabetes, systolic and diastolic blood pressure, total and high-density lipoprotein cholesterol, smoking, age, and sex.

RESULTS

In multivariable-adjusted linear regression analyses adjusted for age and race/ethnicity, high versus low maternal cortisol tertile was associated with 36.7% (95% confidence interval [CI] = 8.4% to 72.5%) greater mean 10-year CHD risk score in women. There was no association in men (-2.8%, 95% CI = -23.8% to 24.0%). Further adjustment for in utero socioeconomic position showed 26.1% (95% CI = -0.5% to 59.9%) greater CHD risk in women. Adjustment for maternal age and size for gestational age had little effect on findings.

CONCLUSIONS

Maternal prenatal cortisol levels were positively associated with 10-year CHD risk among female, and not male, offspring. Adjusting for socioeconomic position during pregnancy reduced effect size in women, suggesting that it may be a common prior factor in both maternal cortisol and CHD risk. These findings provide evidence that targeting mothers who have elevated prenatal cortisol levels, including elevated cortisol in the setting of low socioeconomic position, may potentially reduce long-term CHD risk in their offspring.

Neurophysiological effects of sleep deprivation in healthy adults, a pilot study

Total sleep deprivation (TSD) may induce fatigue, neurocognitive slowing and mood changes, which are partly compensated by stress regulating brain systems, resulting in altered dopamine and cortisol levels in order to stay awake if needed. These systems, however, have never been studied in concert. At baseline, after a regular night of sleep, and the next morning after TSD, 12 healthy subjects performed a semantic affective classification functional magnetic resonance imaging (fMRI) task, followed by a [¹¹C]raclopride positron emission tomography (PET) scan. Saliva cortisol levels were acquired at 7 time points during both days. Affective symptoms were measured using Beck Depression Inventory (BDI), Spielberger State Trait Anxiety Index (STAI) and visual analogue scales. After TSD, perceived energy levels, concentration, and speed of thought decreased significantly, whereas mood did not. During fMRI, response speed decreased for neutral words and positive targets, and accuracy decreased trendwise for neutral words and for positive targets with a negative distracter. Following TSD, processing of positive words was associated with increased left dorsolateral prefrontal activation. Processing of emotional words in general was associated with increased insular activity, whereas contrasting positive vs. negative words showed subthreshold increased activation in the (para)hippocampal area. Cortisol secretion was significantly lower after TSD. Decreased voxel-by-voxel [¹¹C]raclopride binding potential (BP_ND) was observed in left caudate. TSD induces widespread cognitive, neurophysiologic and endocrine changes in healthy adults, characterized by reduced cognitive functioning, despite increased regional brain activity. The blunted HPA-axis response together with altered [¹¹C]raclopride binding in the basal ganglia indicate that sustained wakefulness requires involvement of additional adaptive biological systems.

Self-awakening improves alertness in the morning and during the day after partial sleep deprivation

The ability to awaken at a predetermined time without an alarm is known as self-awakening. Self-awakening improves morning alertness by eliminating sleep inertia; however, the effects of self-awakening on daytime alertness and alertness that has deteriorated as a result of sleep loss are unknown. The aim of this study was to determine the effects of self-awakening on both morning and daytime alertness after partial sleep deprivation. Fifteen healthy males without the habit of self-awakening participated in a cross-over trial including forced awakening and self-awakening conditions. In each condition, participants' sleep was restricted to 5 h per night in their homes for 4 consecutive days. They completed a psychomotor vigilance task and subjective ratings of sleepiness immediately upon awakening each morning. On the fourth day, participants completed subjective ratings of sleepiness, a psychomotor vigilance task and sleep latency tests in the laboratory seven times at 1-h intervals during the day. The response speed on the psychomotor vigilance task, in the morning and during the day, was higher in the self-awakening than the forced awakening condition. Our results showed that self-awakening improved alertness (assessed by response speeds) by reducing sleep inertia and alleviated daytime sleepiness heightened by partial sleep deprivation.