The cortisol awakening response (CAR) is a crucial point of reference within the healthy cortisol circadian rhythm, with cortisol secretion typically peaking between 30 and 45 min post awakening. ...This chapter reviews the history of investigation into the CAR and highlights evidence that its regulation is relatively distinct from cortisol secretion across the rest of the day. It is initiated by awakening, under the influence of the hypothalamic suprachiasmatic nucleus, and "fine tuned" by a direct neural input to the adrenal cortex by the sympathetic nervous system. This chapter also examples the CAR in relation to other awakening-induced processes, such as restoration of consciousness, attainment of full alertness, changes in other hormones, changes in the balance of the immune system, and mobilization of the motor system, and speculates that there is a role for the CAR in these processes.
The cortisol awakening response (CAR) is associated with various aspects of cognition, including executive function, in older adult and clinical samples. However, the association between these ...variables in the healthy functioning population is not well understood due to the limited number of appropriately controlled studies. This study explored the association between the CAR and a set shifting index of executive function in 55 (44 females) healthy participants aged 20.2 ± 3.0 years. Notoriously, assessment of the CAR from self-collected saliva samples within the domestic setting is subject to sample timing error, so electronic monitoring of both awakening and sampling times were employed. Participants attended the laboratory in the afternoon of CAR assessment for testing on the Attention Switching Task of the CANTAB neuropsychological testing battery. A positive association was found between CAR magnitude and attention-switching performance in the afternoon of the same day. This was independent of known relevant CAR covariates, but only evident in CAR data collected without delay exceeding 8 min post-awakening. These findings offer insight into a potential role for the CAR in modulating cognitive functions associated with the pre-frontal cortex.
•Explored the CAR and same day attention switching in 55 healthy young adults.•Positive association between CAR and attention switching performance.•Associations only evident where CAR sampling was accurate to within 8 min.•Results indicate a role for the CAR in healthy pre-frontal cortex function.
Summary Recent evidence suggests that the cortisol awakening response (CAR) on any single day is determined by a combination of trait and state factors; however, the nature of such state associations ...remains largely unexplored. In this study we examined day-to-day changes in the CAR and their covariance with simultaneous changes in sleep-related variables, alcohol consumption, and motility levels. We employed a novel approach to this field of research in the form of a detailed case study of a 27-year-old healthy male (TS) over 50 measurement days, occurring at 3-day intervals. On each measurement day, salivary free cortisol was determined at 0, 15, 30, and 45 min post-awakening and sleep-related variables, alcohol consumption on the previous evening, and post-awakening motility were measured. Our findings show considerable day-to-day variability in the CAR, particularly the dynamic increase, which averaged 17.2 nmol/l and ranged from 3.6 to 39.0 nmol/l (max–min values). We also report a strong relationship between changes in awakening time and changes in the first waking sample (explaining ∼38% of its variability) such that later awakening was associated with a higher first waking sample. This relationship was found to be stronger on days when awakening time was earlier in the morning than on days when it was later. Our findings also provide a preliminary indication for an inverse association between alcohol consumption on the evening before a sampling day and the dynamic of the AUCI , while no associations between sleep quality, post-awakening motility levels, and mode of awakening and measures of the CAR were found.
Changes in the cortisol awakening response (CAR) have been reportedly associated with older age and may reflect changes in cognitive performance. However methodological issues around adherence, in ...regard to careful timing of the CAR, suggest caution in drawing firm conclusions. More investigation is also needed regarding which cognitive domains may be most relevant. Executive Function (EF) is linked strongly to functioning of the frontal cortex, itself linked to cortisol secretion via regulation of the Hypothalamic Adrenocortical Axis. In this study, cortisol profiles, cognitive performance and adherence were carefully assessed in a sample of 50 older participants, aged 60–91years (mean=74years). Key aspects of EF were assessed using Form B of the standard Trail-making Test controlling for time taken to complete the simpler Trail-A form of the test. Strong associations between CAR profiles and EF were evident. Cortisol measures significantly predictive of superior EF-related performance in a regression analysis were: earlier peaking and greater magnitude of the CAR. Together these measures explained fully a quarter of all the variance in test performance (R2=0.25; F=7.90; df=2,47; p<.001). Cognitive tests of declarative memory, often linked to hippocampal functioning, were not associated with CAR profiles. We conclude that in a population of healthy older adults aspects of the CAR may be strongly, and perhaps with some degree of specificity, associated with that domain of cognitive functioning, EF, which seems to depend crucially on the integrity of frontal cortex circuitry.
A relationship between individual differences in trait estimates of the cortisol-awakening response (CAR) and indices of executive function (EF) has been reported. However, it is difficult to ...determine causality from such studies. The aim of the present study was to capitalise upon state variation in both variables to seek stronger support for causality by examining daily co-variation. A 50 days researcher-participant case study was employed, ensuring careful adherence to the sampling protocol. A 24-year-old healthy male collected saliva samples and completed an attention-switching index of EF on the morning of each study day. Subsidiary control measures included wake time, sleep duration, morning fatigue, and amount of prior day exercise and alcohol consumption. As the CAR preceded daily measurement of EF, we hypothesised that, over time, a greater than average CAR would predict better than average EF. This was confirmed by mixed regression modelling of variation in cortisol concentrations, which indicated that the greater the increase in cortisol concentrations from 0 to 30 min post-awakening (CAR) the better was subsequent EF performance at 45 min post-awakening (t = 2.29, p = 0.024). This effect was independent of all potential confounding measures. Results are discussed in terms of implications for the understanding of the relationship between the CAR and the cognitive function, and the previously suggested role of the CAR in "boosting" an individual's performance for the day ahead.
•A greater CAR was associated with a stronger N2.•In CAR responders the CAR was negatively related to the false alarm rate of NoGo-trials.•The CAR predicts response inhibition in the afternoon of the ...same day.
The cortisol awakening response (CAR) is the rapid increase of cortisol levels 30–45 min after awakening in the morning. Numerous studies have indicated the relationship between the CAR and cognition. However, little is known about daily variation in the CAR and cognitive function in healthy adults. The aim of the present study was to investigate whether the CAR predicted the response inhibition function on the same day in both behaviour and the dynamic time course of brain processing. The saliva samples of 47 healthy men were collected at three time points: immediately on awakening, 30 min and 45 min post-awakening in the morning. Participants performed a Go/NoGo task while electroencephalograms (EEG) were recorded in the afternoon of the same day. The results showed that a greater CAR was associated with a stronger N2. In the sub-group of CAR responders (n = 33) the CAR was negatively related to the false alarm rate of NoGo-trials. Our findings suggested that the CAR was predictive of the function of response inhibition in both the earlier cognitive step (i.e., conflict monitoring) and the behavioural performance of response inhibition on the same day in healthy men.
Background: Attachment style has been linked with basal cortisol secretion in healthy adult women. We investigated whether dysregulation in basal cortisol secretion may be evident in younger healthy ...females.
Methods: Sixty healthy females aged 9–18 years (mean 14.16, SD ± 2.63 years) participated in the Attachment Style Interview (ASI). Eight saliva samples, synchronised to awakening, were collected per day on two consecutive weekdays to examine the cortisol awakening response (CAR) and the subsequent diurnal decline.
Results: Participants exhibiting an anxious attachment style had higher cortisol levels on awakening, in contrast to those who were securely attached. The anxious insecure group also showed an attenuated CAR compared to all other participants. Attachment style groups did not differ in cortisol secretion over the remainder of the day.
Conclusions: These findings indicate that the same pattern of cortisol dysregulation associated with disorder in adulthood manifests as a function of anxious (but not avoidant) insecure attachment style in females during healthy childhood and adolescence.
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