The cortisol awakening response and cognition across the adult lifespan

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.

Neuroinflammation, cerebrovascular dysfunction and diurnal cortisol biomarkers in a memory clinic cohort: Findings from the Co-STAR study

Cortisol dysregulation, neuroinflammation, and cerebrovascular dysfunction are biological processes that have been separately shown to be affected in Alzheimer's disease (AD). Here, we aimed to identify biomarker signatures reflecting these pathways in 108 memory clinic patients with subjective cognitive decline (SCD, N = 40), mild cognitive impairment (MCI, N = 39), and AD (N = 29). Participants were from the well-characterized Cortisol and Stress in Alzheimer's Disease (Co-STAR) cohort, recruited at Karolinska University Hospital. Salivary diurnal cortisol measures and 41 CSF proteins were analyzed. Principal component analysis was applied to identify combined biosignatures related to AD pathology, synaptic loss, and neuropsychological assessments, in linear regressions adjusted for confounders, such as age, sex, education and diagnosis. We found increased CSF levels of C-reactive protein (CRP), interferon γ-inducible protein (IP-10), thymus and activation-regulated chemokine (TARC), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in MCI patients. Further, markers of cortisol dysregulation (flattened salivary cortisol awakening response and flattened cortisol slope) correlated with increased levels of placental growth factor (PlGF), IP-10, and chitinase 3-like 1 (YKL-40) in the total cohort. A biosignature composed of cortisol awakening response, cortisol slope, and CSF IL-6 was downregulated in AD patients. Moreover, biomarker signatures reflecting overlapping pathophysiological processes of neuroinflammation and vascular injury were associated with AD pathology, synaptic loss, and worsened processing speed. Our findings suggest an early dysregulation of immune and cerebrovascular processes during the MCI stage and provide insights into the interrelationship of chronic stress and neuroinflammation in AD.

The influence of time of day on memory recognition for faces

Time of day can alter memory performance in general. Its influence on memory recognition performance for faces, which is important for daily encounters with new persons or testimonies, has not been investigated yet. Importantly, high levels of the stress hormone cortisol impair memory recognition, in particular for emotional material. However, some studies also reported high cortisol levels to enhance memory recognition. Since cortisol levels in the morning are usually higher than in the evening, time of day might also influence recognition performance. In this pre-registered study with a two-day design, 51 healthy men encoded pictures of male and female faces with distinct emotional expressions on day one around noon. Memory for the faces was retrieved two days later at two consecutive testing times either in the morning (high and moderately increased endogenous cortisol levels) or in the evening (low endogenous cortisol levels). Additionally, alertness as well as salivary cortisol levels at the different timepoints was assessed. Cortisol levels were significantly higher in the morning compared to the evening group as expected, while both groups did not differ in alertness. Familiarity ratings for female stimuli were significantly better when participants were tested during moderately increased endogenous cortisol levels in the morning than during low endogenous cortisol levels in the evening, a pattern which was previously also observed for stressed versus non-stressed participants. In addition, cortisol levels during that time in the morning were positively correlated with the recollection of face stimuli in general. Thus, recognition memory performance may depend on the time of day and as well as on stimulus type, such as the difference of male and female faces. Most importantly, the results suggest that cortisol may be meaningful and worth investigating when studying the effects of time of day on memory performance. This research offers both, insights into daily encounters as well as legally relevant domains as for instance testimonies.

Diurnal cortisol, neuroinflammation, and neuroimaging visual rating scales in memory clinic patients

BACKGROUND

Neuroinflammation is a hallmark of the Alzheimer's disease (AD) pathogenic process. Cortisol dysregulation may increase AD risk and is related to brain atrophy. This cross-sectional study aims to examine interactions of cortisol patterns and neuroinflammation markers in their association with neuroimaging correlates.

METHOD

134 participants were recruited from the Karolinska University Hospital memory clinic (Stockholm, Sweden). Four visual rating scales were applied to magnetic resonance imaging or computed tomography scans: medial temporal lobe atrophy (MTA), global cortical atrophy (GCA), white matter lesions (WML), and posterior atrophy. Participants provided saliva samples for assessment of diurnal cortisol patterns, and underwent lumbar punctures for cerebrospinal fluid (CSF) sampling. Three cortisol measures were used: the cortisol awakening response, total daily output, and the ratio of awakening to bedtime levels. Nineteen CSF neuroinflammation markers were categorized into five composite scores: proinflammatory cytokines, other cytokines, angiogenesis markers, vascular injury markers, and glial activation markers. Ordinal logistic regressions were conducted to assess associations between cortisol patterns, neuroinflammation scores, and visual rating scales, and interactions between cortisol patterns and neuroinflammation scores in relation to visual rating scales.

RESULT

Higher levels of angiogenesis markers were associated with more severe WML. Some evidence was found for interactions between dysregulated diurnal cortisol patterns and greater neuroinflammation-related biomarkers in relation to more severe GCA and WML. No associations were found between cortisol patterns and visual rating scales.

CONCLUSION

This study suggests an interplay between diurnal cortisol patterns and neuroinflammation in relation to brain structure. While this cross-sectional study does not provide information on causality or temporality, these findings suggest that neuroinflammation may be involved in the relationship between HPA-axis functioning and AD.

Life-course stress, cognition, and diurnal cortisol in memory clinic patients without dementia

AIMS

To examine associations of life-course stress with cognition and diurnal cortisol patterns in older adulthood, as well as potential mediation effects of diurnal cortisol patterns and perceived stress on the association between life-course stress and cognition.

METHODS

127 participants without dementia were selected from a cohort of Swedish memory clinic patients. Cross-sectional associations between scores on two chronic stress questionnaires (perceived stress, stressful life events (SLEs)), five cognitive domains (overall cognition, memory, working memory, processing speed, perceptual reasoning), and two measures of diurnal cortisol patterns (total daily output, diurnal cortisol slope), as well as potential mediation effects of diurnal cortisol patterns and perceived stress on associations between life-course stress and cognition, were assessed using linear regressions.

RESULTS

Greater lifetime exposure to SLEs was associated with worse memory, working memory, and processing speed performance, but not with diurnal cortisol patterns. A greater number of SLEs in late childhood was associated with worse working memory and processing speed, while a greater number of SLEs in non-recent adulthood were associated with better overall cognition and perceptual reasoning. Greater perceived stress was associated with a flattened diurnal cortisol slope, but not with cognition. No evidence for interplay between self-reported and physiological stress markers was found in relation to cognition, although there appeared to be a significant positive indirect association between economic/legal SLEs and the diurnal cortisol slope via perceived stress.

CONCLUSIONS

The associations between SLEs and cognition depend on the period during which SLEs occur, but seem independent of late-life cortisol dysregulation.

The Biology of Stress Intolerance in Patients with Chronic Pain—State of the Art and Future Directions

Stress has been consistently linked to negative impacts on physical and mental health. More specifically, patients with chronic pain experience stress intolerance, which is an exacerbation or occurrence of symptoms in response to any type of stress. The pathophysiological mechanisms underlying this phenomenon remain unsolved. In this state-of-the-art paper, we summarised the role of the autonomic nervous system (ANS) and hypothalamus-pituitary-adrenal (HPA) axis, the two major stress response systems in stress intolerance. We provided insights into such mechanisms based on evidence from clinical studies in both patients with chronic pain, showing dysregulated stress systems, and healthy controls supported by preclinical studies, highlighting the link between these systems and symptoms of stress intolerance. Furthermore, we explored the possible regulating role for (epi)genetic mechanisms influencing the ANS and HPA axis. The link between stress and chronic pain has become an important area of research as it has the potential to inform the development of interventions to improve the quality of life for individuals living with chronic pain. As stress has become a prevalent concern in modern society, understanding the connection between stress, HPA axis, ANS, and chronic health conditions such as chronic pain is crucial to improve public health and well-being.

Understanding the relationships between physiological and psychosocial stress, cortisol and cognition

Stress is viewed as a state of real or perceived threat to homeostasis, the management of which involves the endocrine, nervous, and immune systems. These systems work independently and interactively as part of the stress response. The scientific stress literature, which spans both animal and human studies, contains heterogeneous findings about the effects of stress on the brain and the body. This review seeks to summarise and integrate literature on the relationships between these systems, examining particularly the roles of physiological and psychosocial stress, the stress hormone cortisol, as controlled by the hypothalamic-pituitary-adrenal (HPA) axis, and the effects of stress on cognitive functioning. Health conditions related to impaired HPA axis functioning and their associated neuropsychiatric symptoms will also be considered. Lastly, this review will provide suggestions of clinical applicability for endocrinologists who are uniquely placed to measure outcomes related to endocrine, nervous and immune system functioning and identify areas of intervention.

Association between Intelligence Quotient Dental Anxiety and Oral Health-related Quality of Life in Children: A Cross-sectional Study

Background

Determining the intelligence quotient (IQ) grades of children help in managing dental anxiety (DA) and maintaining the good oral health-related quality of life (OHRQoL).

Aim

To assess the association between IQ, DA, and OHRQoL in children aged 10-11 years.

Design

This cross-sectional study was carried out among 202 children aged 10-11 years in the Southern part of Tamil Nadu, India. The IQ level, DA, and OHRQoL were measured using Raven's Coloured Progressive Matrices (RCPM), Children's Fear Survey Schedule-Dental Subscale (CFSS-DS), and Child Oral Health Impact Profile Short Form (COHIP-SF) 19, respectively. Chi-squared test and Spearman rank order correlation test were used for analysis.

Results

The results revealed a significant negative correlation (p < 0.05; r = -0.239) between IQ and OHRQoL. DA was negatively correlated with IQ (r = -0.093) and OHRQoL (r = -0.065), but it was not statistically significant. The gender-based comparison revealed no significant difference in the distribution of girls and boys within different grades of IQ levels (p = 0.74), DA (p = 0.29), and OHRQoL (p = 0.85).

Conclusion

Children with higher IQ showed low OHRQoL scores. DA was negatively correlated with IQ and OHRQoL.

How to cite this article

Asokan S, PR GP, Mathiazhagan T, et al. Association between Intelligence Quotient Dental Anxiety and Oral Health-related Quality of Life in Children: A Cross-sectional Study. Int J Clin Pediatr Dent 2022;15(6):745-749.

Cortisol, cognition and Alzheimer's disease biomarkers among memory clinic patients

Objective

This study aims to investigate the relationship between diurnal cortisol patterns, cognition and Alzheimer's disease (AD) biomarkers in memory clinic patients.

Method

Memory clinic patients were recruited from Karolinska University Hospital in Sweden (n=155). Diurnal cortisol patterns were assessed using five measures: awakening levels, cortisol awakening response, bedtime levels, the ratio of awakening to bedtime levels (AM/PM ratio) and total daily output. Cognition was measured in five domains: memory, working memory, processing speed, perceptual reasoning and overall cognition. AD biomarkers Aβ42, total tau and phosphorylated tau were assessed from cerebrospinal fluid (CSF). Cognition was measured at follow-up (average 32 months) in a subsample of participants (n=57).

Results

In assessing the associations between cortisol and cognition, higher awakening cortisol levels were associated with greater processing speed at baseline. No relationship was found between diurnal cortisol patterns and change in cognition over time or CSF AD biomarkers in the total sample. After stratification by CSF Aβ42 levels, higher awakening cortisol levels were associated with worse memory performance in amyloid-positive participants. In amyloid-negative participants, higher bedtime cortisol levels and a lower AM/PM ratio were associated with lower overall cognition, greater awakening cortisol levels were associated with better processing speed, and a higher AM/PM ratio was associated with better perceptual reasoning. Additionally, higher awakening cortisol levels were associated with lower CSF Aβ42 levels in amyloid-positive participants, while higher bedtime cortisol levels and a lower AM/PM ratio were associated with higher CSF total tau in amyloid-negative participants.

Conclusions

Our findings suggest that diurnal cortisol patterns are associated with cognitive function and provide new insights into the association between diurnal cortisol patterns and AD-related CSF biomarkers. Further research is needed to examine the complex relationship between cortisol, cognition and brain pathology.

Alterations in Cortisol Profiles among Mothers of Children with ASD Related to Poor Child Sleep Quality

Caregivers of children with autism spectrum disorder (ASD) experience poorer sleep, but studies have not yet used objective measures to investigate how child and caregiver sleep affect each other. In this study, 29 mothers and their child with ASD aged between 6 and 16 years were recruited. Questionnaires measuring child autism, maternal depression, and maternal and child sleep quality were administered. Cortisol salivary samples were also obtained from the mothers over the course of a day. Results revealed that maternal depression is significantly correlated with their subjective sleep quality, sleep latency and daytime dysfunction. Child sleep quality was also found to be significantly correlated with ASD severity. In terms of maternal cortisol profiles, a significant number of mothers showed a flattened diurnal cortisol expression, and children of mothers with a flattened cortisol profile had significantly more sleep problems. Overall, results suggest that maternal and child sleep are affected by the child’s disability but also are mutually related. Future studies may consider employing measures such as actigraphy or somnography to quantify sleep quality and establish causal pathways between sleep, cortisol expression and caregiver and child outcomes. The present study has clinical implications in examining family sleep when considering treatment for ASD.

Mediation of perceived stress and cortisol in the association between neuroticism and global cognition in older adults: A longitudinal study

Neuroticism has been associated with a greater dementia risk, but its association with cognitive decline in healthy older adults remains unclear. Stress has been proposed as one of the mechanisms that could explain this relationship. Our aim was to analyse, in healthy older people, the mediating role of perceived stress and the Hypothalamic-Pituitary-Adrenal (HPA) axis in the association between neuroticism and global cognition. At Waves 1 and 2 (4-year follow-up), 87 older people (49.4% women; M age = 65.08, SD = 4.54 at Wave 1) completed a neuropsychological battery and the Perceived Stress Scale (PSS), and provided saliva samples on two (Wave 1) and three (Wave 2) consecutive days to measure the wake-to-bed slope. In Wave 2, neuroticism was assessed with the NEO-Five-Factor Inventory. PSS, but not the wake-to-bed slope, mediated the negative associations between neuroticism and global cognition (Waves 1, 2 and change). Regarding gender differences, PSS (Waves 1, 2 and change) and the wake-to-bed slope (Wave 2 and change) mediated these associations in men. Our results suggest that perceived stress and HPA-axis dysregulation could act as mechanisms underlying the association between neuroticism and cognitive functioning and decline, at least in older men.

Under Which Circumstances Does Academic Workload Lead to Stress?

Abstract. Academic stress is associated with a wide range of adverse outcomes, including detrimental effects on mental health, achievement, and well-being. Numerous studies have shown an association between the cortisol awakening response (CAR) and various health and risk factors. Some studies revealed a protective function of the CAR as a stress buffer preventing the stress system from overshooting. We investigated the moderating effect of the CAR on the within-subject association between academic workload and academic stress in participants’ daily lives using ambulatory assessment. We assessed 77 undergraduate university participants for 2 days at the beginning of the semester and approximately 3 months later, individually starting one week before an exam. Participants provided academic stress and academic workload ratings hourly during their waking time using smartphone-based e-diaries and salivary cortisol samples at awakening as well as 30, 45, and 60 min later on two consecutive days during each of the assessment waves. Average within-subject associations between academic workload and academic stress were analyzed using multilevel models. Interactions with indicators of the cortisol awakening response (CAR) were included to test moderating effects of the CAR on the workload-stress associations. There was a significant positive within-subject association between academic workload and academic stress. Significant cross-level interactions showed a moderating effect of the CAR on this association. The results point out the importance of the CAR in the regulation of the workload-stress associations in academic life and underscore the relevance of investigating the influence of specific stressor-dependent reciprocal effects of the CAR on learning and experienced stress.

The cortisol awakening response and the late positive potentials evoked by unpleasant emotional pictures in healthy adults

The cortisol awakening response (CAR) refers to a sharp rise in cortisol concentrations within the 45 min following morning awakening. Alterations in CAR have been associated with various internalizing symptoms and brain function. The current study aimed to investigate the association between CAR and neural activity in response to unpleasant emotional pictures. A total of 46 healthy adults (22.55 years ± 1.69) collected saliva samples at 0, 30, and 45 min post-awakening on two days to assess the CAR. In the afternoon after CAR measurement on the first day, electroencephalograms were recorded when the participants completed a passive viewing task. The results showed that a greater CAR was associated with a decreased late positive potential difference score between unpleasant and neutral stimuli. This finding indicates that a larger CAR may be associated with decreased attentional engagement to unpleasant emotional information in healthy adults.

Stress-Hormone Dynamics and Working Memory in Healthy Women Who Use Oral Contraceptives Versus Non-Users

BACKGROUND

Women who use oral contraceptives (OCs) may have a higher risk of developing a depression, which is associated with both vulnerability to stress and cognitive dysfunction. OCs disrupt the hypothalamic-pituitary-gonadal (HPG) axis by suppressing endogenous sex steroid production including estradiol. The HPG axis and the hypothalamic-pituitary-adrenal (HPA) axis are known to interact, possibly through modulations driven by estradiol. OCs may affect HPA regulation capacity, i.e., disturb cortisol dynamics such as the cortisol awakening response (CAR), and influence cognition such as working memory (WM). We hypothesize that OC use is associated with blunted cortisol dynamics and impaired WM performance relative to non-users.

METHODS

Data from 78 healthy women in the reproductive age were available from the CIMBI database. We evaluated if CAR and WM differed between OC users (n=25) and non-users (n=53) and if the level of estradiol modulated the OC use effect on CAR or WM in generalized least square models.

RESULTS

We found that OC users had a blunted CAR (p= 0.006) corresponding to a 61% reduction relative to non-users; however, no estradiol-BY-OC use interaction effect was observed on CAR. Also, OC users had higher cortisol levels at awakening compared to non-users (p = 0.03). We observed no effect of OC use or an estradiol-BY-OC use interaction effect on WM. Also, within the OC user group, neither CAR nor WM was associated with suppressed estradiol. CAR was not associated with WM.

CONCLUSION

Healthy women who use OCs have blunted cortisol dynamics relative to non-users. However, we could not detect OC use effects on working memory in our sample size. We speculate that disrupted cortisol dynamics may be important for the emergence of depressive symptoms in OC users.

Stress, the cortisol awakening response and cognitive function

There is evidence that stress-induced disruption of the circadian rhythm of cortisol secretion, has negative consequences for brain health. The cortisol awakening response (CAR) is the most prominent and dynamic aspect of this rhythm. It has complex regulatory mechanisms making it distinct from the rest of the cortisol circadian rhythm, and is frequently investigated as a biomarker of stress and potential intermediary between stress and impaired brain function. Despite this, the precise function of the CAR within the healthy cortisol circadian rhythm remains poorly understood. Cortisol is a powerful hormone known to influence cognition in multiple and complex ways. Studies of the CAR and cognitive function have used varied methodological approaches which have produced similarly varied findings. The present review considers the accumulating evidence linking stress, attenuation of the CAR and reduced cognitive function, and seeks to contextualize the many findings to study populations, cognitive measures, and CAR methodologies employed. Associations between the CAR and both memory and executive functions are discussed in relation to its potential role as a neuroendocrine time of day signal that synchronizes peripheral clocks throughout the brain to enable optimum function, and recommendations for future research are provided.

The relationship between loneliness and cognition in healthy older men and women: The role of cortisol

Loneliness has been associated with an increased risk of cognitive decline and dementia in older people, as well as a dysregulation of Hypothalamic-Pituitary-Adrenal (HPA) axis functioning. In addition, it has been suggested that women are more vulnerable to the negative effects of loneliness on health. Our aim was to analyze the effect of HPA-axis functioning as a mediator in the relationship between loneliness and cognitive function, and interactions depending on sex, in healthy older people. To do so, 86 healthy older people (52.3% female) from 60 to 80 years old (M = 67.44, SD = 4.37) completed the revised UCLA loneliness scale. A neuropsychological battery was administered to assess global cognition, processing speed, attention and executive function, working memory, and verbal memory immediate and delayed recall. Saliva samples were provided on two consecutive weekdays to obtain awakening and bedtime cortisol levels, the diurnal cortisol slope (DCS), and the area under the curve with respect to the ground (AUCg). Our results showed that loneliness was not directly associated with cognitive performance. Furthermore, loneliness was related to higher bedtime cortisol levels, but not to awakening cortisol, the DCS, or the AUCg. In addition, loneliness was associated with worse performance on attention and processing speed, executive function, and verbal memory immediate recall, via bedtime cortisol levels. Therefore, we suggest that HPA-axis functioning is one of the biological mechanisms that mediate the relationship between loneliness and poorer cognitive function. No sex differences were observed in these associations.

Age differences in the relationship between cortisol and emotional memory

Research has shown that remembering emotional information can occur at the expense of surrounding neutral background information; this emotional memory trade-off occurs similarly in both younger and older adults. We investigated how levels of cortisol, a hormone that acts on the central nervous system, impact emotional memory with age. Younger and older adult participants incidentally encoded emotional (positive, negative, or neutral) items placed on neutral backgrounds and later completed recognition tests for both the items and the backgrounds. Cortisol was measured at multiple time points to assess basal cortisol. Results are reported for prelearning levels, as findings were comparable across time points. Results revealed that higher levels of cortisol predicted a lower memory trade-off effect for older adults compared to younger adults and that this age difference in the role of cortisol tended to be strongest for memory for negative items (rather than for backgrounds or neutral items). No such interaction emerged for the positive trade-off effect. These results suggest that cortisol levels play a different role in supporting emotional memory across the life span, with lower levels of cortisol potentially more adaptive for memory for negative emotional information and higher levels indicating potential impairment with age. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Diurnal Cortisol Dynamics, Perceived Stress, and Language Production in Aphasia

Purpose The current study investigated diurnal cortisol dynamics in adults with and without aphasia, along with subjective reports of stress and measures of language production. Dysregulation of cortisol, a common biomarker of stress, is associated with cognitive dysfunction in different clinical populations. However, little is known about the consequences of stress-induced cortisol disturbances for stroke survivors, including those with aphasia. Method Nineteen participants with aphasia and 14 age-matched neurotypical adults were tested. Saliva samples were collected from participants to assess the cortisol awakening response, a marker of the integrity of the hypothalamic-pituitary-adrenal (HPA) axis. Participants also completed 2 subjective stress questionnaires. Language was evaluated using 3 short, picture description narratives, analyzed for discourse (dys)fluency and productivity markers. Results In contrast to neurotypical participants, adults with aphasia did not show the predictable cortisol awakening response. Participants with aphasia also showed an unusual heightened level of cortisol upon awakening. Additionally, neurotypical participants demonstrated an association between intact language performance and the cortisol awakening response, whereas the participants with aphasia did not, although they did perceive the language tasks as stressful. Conclusion This study indicates that the functionality of the HPA axis, as indexed by cortisol, contributes to optimal language performance in healthy adults. The absence of an awakening response among participants with aphasia suggests that stroke leads to dysregulation of the HPA axis, although the degree to which this impairment affects language deficits in this population requires further investigation.

Exercise, the diurnal cycle of cortisol and cognitive impairment in older adults

Exercise has been shown to reduce the risk of developing Mild Cognitive Impairment and Alzheimer's disease as well as to improve cognition in healthy and cognitively impaired individuals. However, the mechanisms of these benefits are not well understood. The stress hypothesis suggests that the cognitive benefits attributed to exercise may partially be mediated by changes in the cortisol secretion pattern. Chronic stress may increase the risk of AD and exacerbate the cognitive deficits and brain pathology characteristic of the condition while physical activity has been shown to attenuate most of stress consequences and risk factors for AD. Initially, research on the effects of cortisol on cognition and physical activity focused on cortisol levels at one time point but the circadian pattern of cortisol secretion is complex and it is still unclear which aspects are most closely associated with cognitive function. Thus, the aim of this review was to analyze the exercise/stress/cognition hypothesis focusing on the effects of the diurnal cycle of cortisol on cognitive function and physical activity in older adults with and without cognitive impairment.

Bioconversion of Corticosterone into Corticosterone-Glucoside by Glucosyltransferase

Glucosylation of the 21-hydroxyl group of glucocorticoid changes its solubility into hydrophilicity from hydrophobicity and, as with glucocorticoid glucuronides as a moving object in vivo, it is conceivable that it exhibits the same behavior. Therefore, glucosylation to the 21-hydroxyl group while maintaining the 11β-hydroxyl group is particularly important, and glucosylation of corticosterone was confirmed by high-resolution mass spectrometry and 1D (¹H and ¹³C) and 2D (COSY, ROESY, HSQC-DEPT and HMBC) NMR. Moreover, the difference in bioactivity between corticosterone and corticosterone 21-glucoside was investigated in vitro. Corticosterone 21-glucoside showed greater neuroprotective effects against H₂O₂-induced cell death and reactive oxygen species (ROS) compared with corticosterone. These results for the first time demonstrate that bioconversion of corticosterone through the region-selective glucosylation of a novel compound can present structural potential for developing new neuroprotective agents.

Elevated cortisol awakening response associated with early life stress and impaired executive function in healthy adult males

Experiencing early life stress (ELS) and subsequent dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis may play a role in the aetiology of mental health disorders. However, the exact mechanisms linking HPA-axis dysregulation with the development of psychopathology have not been fully delineated. Progress in this area is hampered by the complex and often conflicting associations found between markers of HPA-axis function and risk factors for mental health disorders such as impaired executive function (EF) and ELS. This study investigated the association of the cortisol awakening response (CAR) with ELS and EF in a healthy adult male population (n=109, aged 21-63). As previous inconsistencies in CAR and ELS association studies may be the result of not considering ELS-related factors such as cumulative exposure, type of stressor and developmental timing of ELS, these were also investigated. The main findings were that the CAR was significantly elevated in individuals reporting ELS compared to those reporting no ELS (p=0.007) and that an elevated CAR predicted poorer problem solving/planning (p=0.046). Cumulative exposure, type of stressor and developmental timing of ELS were also found to impact significantly on the CAR. These results suggest that ELS is associated with chronic changes in HPA-axis function and that these changes may be associated with impairments in problem solving/planning. Future work should investigate further the neurobiological mechanisms linking ELS, the CAR and EF and their role in conferring risk for the development of mental health disorders.

Assessment of the cortisol awakening response: Real-time analysis and curvilinear effects of sample timing inaccuracy

The cortisol awakening response (CAR) is typically measured in the domestic setting. Moderate sample timing inaccuracy has been shown to result in erroneous CAR estimates and such inaccuracy has been shown partially to explain inconsistency in the CAR literature. The need for more reliable measurement of the CAR has recently been highlighted in expert consensus guidelines where it was pointed out that less than 6% of published studies provided electronic-monitoring of saliva sampling time in the post-awakening period. Analyses of a merged data-set of published studies from our laboratory are presented. To qualify for selection, both time of awakening and collection of the first sample must have been verified by electronic-monitoring and sampling commenced within 15min of awakening. Participants (n=128) were young (median age of 20 years) and healthy. Cortisol values were determined in the 45min post-awakening period on 215 sampling days. On 127days, delay between verified awakening and collection of the first sample was less than 3min ('no delay' group); on 45days there was a delay of 4-6min ('short delay' group); on 43days the delay was 7-15min ('moderate delay' group). Cortisol values for verified sampling times accurately mapped on to the typical post-awakening cortisol growth curve, regardless of whether sampling deviated from desired protocol timings. This provides support for incorporating rather than excluding delayed data (up to 15min) in CAR analyses. For this population the fitted cortisol growth curve equation predicted a mean cortisol awakening level of 6nmols/l (±1 for 95% CI) and a mean CAR rise of 6nmols/l (±2 for 95% CI). We also modelled the relationship between real delay and CAR magnitude, when the CAR is calculated erroneously by incorrectly assuming adherence to protocol time. Findings supported a curvilinear hypothesis in relation to effects of sample delay on the CAR. Short delays of 4-6min between awakening and commencement of saliva sampling resulted in an overestimated CAR. Moderate delays of 7-15min were associated with an underestimated CAR. Findings emphasize the need to employ electronic-monitoring of sampling accuracy when measuring the CAR in the domestic setting.