Salivary cortisol, brain volumes, and cognition in community-dwelling elderly without dementia

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.

Examining HPA-axis functioning as a mediator of the relationship between depression and cognition across the adult lifespan

Altered HPA-axis functioning is a hypothesized mechanism for worsened cognition in depression. The current study examines the indirect effects of depression on processing speed, executive functioning, and memory as a function of the HPA-axis. 38 individuals with a depression diagnosis and 50 healthy controls (HCs) aged 18-86 underwent neuropsychological testing and at-home diurnal salivary cortisol collection. Depression was assessed via structured clinical interviews and rating scales. Cognitive composite scores were derived from factor analysis. Daytime cortisol exposure was estimated using area under the curve (AUC). Depression was associated with higher cortisol levels and slower processing speed . A significant suppression effect of AUC was present on the relationship between depression and processing speed. Limitations include the cross-sectional design and limited sample heterogeneity. Though poorly modulated HPA-axis is one proposed mechanism of cognitive alterations in depression, our results did not support this conclusion for processing speed. Alternative mechanisms should be considered to inform interventions to target cognitive alterations in depression.

Aerobic exercise increases cortisol awakening response in older adults

Evidence from both preclinical and clinical studies suggests aerobic exercise may dampen age-related decline in cognitive performance. Alterations in hypothalamic-pituitary-adrenal (HPA) axis function and reactivity may be a mechanism by which aerobic exercise benefits cognitive performance, and reduces perceived stress. This investigation was completed as an ancillary investigation of the Brain in Motion (BIM) study, a 6-month supervised aerobic exercise intervention. Participants were generally healthy and screened for inclusion/exclusion criteria for the parent study. Thirty-eight participants were recruited (Mean age = 65.0 [SD = 5.1]; 60% female) and the final longitudinal sample was 32 participants. Participants provided a passive drool sample at: waking, 15, 30, and 45 min post-waking to assess the cortisol awakening response (CAR) and 3, 6, 9, and 12 h post-waking to assess daily area under the curve for cortisol. Salivary cortisol was quantified by liquid chromatography coupled to tandem mass spectrometry. The exercise intervention increased CAR but no differences were observed in daily AUC. In addition, larger increases in CAR were positively associated with greater decreases in subjective stress. Thus, aerobic exercise improved the CAR in otherwise healthy, but sedentary older adults and greater improvements in CAR were associated with greater reductions in perceived stress.

Dysregulation of the hypothalamic pituitary adrenal (HPA) axis and cognitive capability at older ages: individual participant meta-analysis of five cohorts

Evidence on the association between functioning of the hypothalamic pituitary adrenal (HPA) axis and cognitive capability at older ages is mixed. We undertook a systematic review (until October 2016) and individual participant data (IPD) meta-analysis to test if dysregulation of the HPA axis is associated with worse cognitive capability. Five cohort studies were included in the IPD meta-analysis of diurnal cortisol patterns with crystallised and fluid cognitive ability. Higher night time cortisol was associated with worse fluid ability (standardised coefficient per SD increase −0.063, 95% CI −0.124, −0.002, P = 0.04; I² = 79.9%; age and gender adjusted). A larger diurnal drop was associated with better fluid ability (standardised coefficient per SD increase 0.037, 95% CI 0.008, 0.065, P = 0.01; I² = 49.2%; age and gender adjusted). A bigger cortisol awakening response (CAR) was weakly associated with better fluid (P = 0.09; I² = 0.0%; age and gender adjusted) and crystallised (P = 0.10; I² = 0.0%; age and gender adjusted) ability. There is weak evidence that a greater diurnal decline of the HPA axis and a larger CAR are associated with improvements in cognition at older ages. As associations are cross-sectional, we cannot rule out reverse causation.

High Cortisol and the Risk of Dementia and Alzheimer's Disease: A Review of the Literature

Introduction: Cortisol effects on the brain are exerted through two distinct receptors, inducing complex and even opposite effects on the cerebral structures implicated in the various cognitive functions. High cortisol may also have deleterious effects on the brain structures and contribute to neurodegeneration, in particular Alzheimer’s disease (AD), via different mechanisms.

Objective: To examine the interrelationships between cortisol, cognitive impairment and AD.

Methods: Review of the literature.

Results: Clinical studies found that elevated cortisol was associated with poorer overall cognitive functioning, as well as with poorer episodic memory, executive functioning, language, spatial memory, processing speed, and social cognition; while in animals, glucocorticoid administration resulted in cognitive impairment and abnormal behavior. In cognitively healthy subjects, higher cortisol levels have been associated with an increased risk of cognitive decline and AD. Subjects with dementia and Mild Cognitive Impairment (MCI) due to AD have been found to have higher CSF cortisol levels than cognitively healthy controls. Elevated CSF cortisol may also be associated with a more rapid cognitive decline in MCI due to AD. Elevated cortisol levels have been also found in delirium. High cortisol may mediate the impact of stressful life events, high neuroticism, depression, sleep disturbances, as well as cardiovascular risk factors on cognitive performance, neurodegeneration, and cognitive decline. High cortisol may also exert neurotoxic effects on the hippocampus, and promote oxidative stress and amyloid β peptide toxicity. Further possible underlying mechanisms include the interactions of cortisol with inflammatory mediators, neurotransmitters, and growth factors.

Conclusion: Elevated cortisol levels may exert detrimental effects on cognition and contribute to AD pathology. Further studies are needed to investigate cortisol-reducing and glucocorticoidreceptor modulating interventions to prevent cognitive decline.

Circulating cortisol and cognitive and structural brain measures: The Framingham Heart Study

OBJECTIVE

To assess the association of early morning serum cortisol with cognitive performance and brain structural integrity in community-dwelling young and middle-aged adults without dementia.

METHODS

We evaluated dementia-free Framingham Heart Study (generation 3) participants (mean age 48.5 years, 46.8% men) who underwent cognitive testing for memory, abstract reasoning, visual perception, attention, and executive function (n = 2,231) and brain MRI (n = 2018) to assess total white matter, lobar gray matter, and white matter hyperintensity volumes and fractional anisotropy (FA) measures. We used linear and logistic regression to assess the relations of cortisol (categorized in tertiles, with the middle tertile as referent) to measures of cognition, MRI volumes, presence of covert brain infarcts and cerebral microbleeds, and voxel-based microstructural white matter integrity and gray matter density, adjusting for age, sex, APOE, and vascular risk factors.

RESULTS

Higher cortisol (highest tertile vs middle tertile) was associated with worse memory and visual perception, as well as lower total cerebral brain and occipital and frontal lobar gray matter volumes. Higher cortisol was associated with multiple areas of microstructural changes (decreased regional FA), especially in the splenium of corpus callosum and the posterior corona radiata. The association of cortisol with total cerebral brain volume varied by sex (p for interaction = 0.048); higher cortisol was inversely associated with cerebral brain volume in women (p = 0.001) but not in men (p = 0.717). There was no effect modification by the APOE4 genotype of the relations of cortisol and cognition or imaging traits.

CONCLUSION

Higher serum cortisol was associated with lower brain volumes and impaired memory in asymptomatic younger to middle-aged adults, with the association being evident particularly in women.

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.

Stress-induced corticosterone secretion covaries with working memory in aging

A substantial literature details the relationship between age-related changes to the hypothalamic-pituitary-adrenal axis and deterioration of mnemonic functions that depend on the hippocampus. The relationship between adrenocortical status and other forms of memory that depend on the prefrontal cortex is less well understood in the context of advanced age. Here, we characterized performance of young adult and aged F344 rats on a prefrontal cortex-dependent working memory task and subsequently measured corticosterone (CORT) levels over the diurnal cycle and during exposure to an acute stressor. Our analyses revealed that aged rats with better working memory mounted a greater CORT response during acute stress exposure than either young adults or age-matched rats with impaired working memory. We also observed that age-related elevation of basal CORT levels is not associated with working memory performance. Jointly, these data reveal that the hypothalamic-pituitary-adrenal axis-mediated response to acute stress is positively associated with working memory in aging.

Longitudinal relationships among depressive symptoms, cortisol, and brain atrophy in the neocortex and the hippocampus

OBJECTIVE

Depression is associated with accelerated aging and age-related diseases. However, mechanisms underlying this relationship remain unclear. The aim of this study was to longitudinally assess the link between depressive symptoms, brain atrophy, and cortisol levels.

METHOD

Participants from the Betula prospective cohort study (mean age = 59 years, SD = 13.4 years) underwent clinical, neuropsychological and brain 3T MRI assessments at baseline and a 4-year follow-up. Cortisol levels were measured at baseline in four saliva samples. Cortical and hippocampal atrophy rates were estimated and compared between participants with and without depressive symptoms (n = 81) and correlated with cortisol levels (n = 49).

RESULTS

Atrophy in the left superior frontal gyrus and right lingual gyrus developed in parallel with depressive symptoms, and in the left temporal pole, superior temporal cortex, and supramarginal cortex after the onset of depressive symptom. Depression-related atrophy was significantly associated with elevated cortisol levels. Elevated cortisol levels were also associated with widespread prefrontal, parietal, lateral, and medial temporal atrophy.

CONCLUSION

Depressive symptoms and elevated cortisol levels are associated with atrophy of the prefrontal and limbic areas of the brain.

The Aerobic and Cognitive Exercise Study (ACES) for Community-Dwelling Older Adults With or At-Risk for Mild Cognitive Impairment (MCI): Neuropsychological, Neurobiological and Neuroimaging Outcomes of a Randomized Clinical Trial

Prior research has found that cognitive benefits of physical exercise and brain health in older adults may be enhanced when mental exercise is interactive simultaneously, as in exergaming. It is unclear whether the cognitive benefit can be maximized by increasing the degree of mental challenge during exercise. This randomized clinical trial (RCT), the Aerobic and Cognitive Exercise Study (ACES) sought to replicate and extend prior findings of added cognitive benefit from exergaming to those with or at risk for mild cognitive impairment (MCI). ACES compares the effects of 6 months of an exer-tour (virtual reality bike rides) with the effects of a more effortful exer-score (pedaling through a videogame to score points). Fourteen community-dwelling older adults meeting screening criteria for MCI (sMCI) were adherent to their assigned exercise for 6 months. The primary outcome was executive function, while secondary outcomes included memory and everyday cognitive function. Exer-tour and exer-score yielded significant moderate effects on executive function (Stroop A/C; d's = 0.51 and 0.47); there was no significant interaction effect. However, after 3 months the exer-tour revealed a significant and moderate effect, while exer-score showed little impact, as did a game-only condition. Both exer-tour and exer-score conditions also resulted in significant improvements in verbal memory. Effects appear to generalize to self-reported everyday cognitive function. Pilot data, including salivary biomarkers and structural MRI, were gathered at baseline and 6 months; exercise dose was associated with increased BDNF as well as increased gray matter volume in the PFC and ACC. Improvement in memory was associated with an increase in the DLPFC. Improved executive function was associated with increased expression of exosomal miRNA-9. Interactive physical and cognitive exercise (both high and low mental challenge) yielded similarly significant cognitive benefit for adherent sMCI exercisers over 6 months. A larger RCT is needed to confirm these findings. Further innovation and clinical trial data are needed to develop accessible, yet engaging and effective interventions to combat cognitive decline for the growing MCI population.

ClinicalTrials.gov ID: NCT02237560

Cerebral Structure and Cognitive Performance in African Americans and European Americans With Type 2 Diabetes

Background

African Americans typically perform worse than European Americans on cognitive testing. Contributions of cardiovascular disease (CVD) risk factors and educational quality to cognitive performance and brain volumes were compared in European Americans and African Americans with type 2 diabetes.

Methods

Association between magnetic resonance imaging-determined cerebral volumes of white matter (WMV), gray matter (GMV), white matter lesions (WMLV), hippocampal GMV, and modified mini-mental state exam (3MSE), digit symbol coding (DSC), Rey Auditory Verbal Learning Test (RAVLT), Stroop, and verbal fluency performance were assessed in Diabetes Heart Study Memory in Diabetes (MIND) participants. Marginal models incorporating generalized estimating equations were employed with serial adjustment for risk factors.

Results

The sample included 520 African Americans and 684 European Americans; 56 per cent female with mean ± SD age 62.8 ± 10.3 years and diabetes duration 14.3 ± 7.8 years. Adjusting for age, sex, diabetes duration, BMI, HbA1c, total intracranial volume, scanner, statins, CVD, smoking, and hypertension, WMV (p = .001) was lower and WMLV higher in African Americans than European Americans (p = .001), with similar GMV (p = .30). Adjusting for age, sex, education, HbA1c, diabetes duration, hypertension, BMI, statins, CVD, smoking, and depression, poorer performance on 3MSE, RAVLT, and DSC were seen in African Americans (p = 6 × 10-23-7 × 10-62). Racial differences in cognitive performance were attenuated after additional adjustment for WMLV and nearly fully resolved after adjustment for wide-range achievement test (WRAT) performance (p = .0009-.65).

Conclusions

African Americans with type 2 diabetes had higher WMLV and poorer cognitive performance than European Americans. Differences in cognitive performance were attenuated after considering WMLV and apparent poorer educational quality based on WRAT.

Brain structural changes in late-life generalized anxiety disorder

Late-life Generalized Anxiety Disorder (GAD) is relatively understudied and the underlying structural and functional neuroanatomy has received little attention. In this study, we compare the brain structural characteristics in white and gray matter in 31 non-anxious older adults and 28 late-life GAD participants. Gray matter indices (cortical thickness and volume) were measured using FreeSurfer parcellation and segmentation, and mean diffusivity was obtained through Diffusion Tensor Imaging (DTI). We assessed both macroscopic white matter changes [using white matter hyperintensity (WMH) burden] and microscopic white matter integrity [using fractional anisotropy (FA)]. No differences in macro- or microscopic white matter integrity were found between GAD and non-anxious controls (HC). GAD participants had lower cortical thickness in the orbitofrontal cortex (OFC), inferior frontal gyrus, and pregenual anterior cingulate cortex (ACC). Higher worry severity was associated with gray matter changes in OFC, ACC and the putamen. The results did not survive the multiple comparison correction, but the effect sizes indicate a moderate effect. The study suggests that late-life GAD is associated with gray matter changes in areas involved in emotion regulation, more so than with white matter changes. We conclude that anxiety-related chronic hypercortisolemia may have a dissociative effect on gray and white matter integrity.

Short-term mechanisms influencing volumetric brain dynamics

With the use of magnetic resonance imaging (MRI) and brain analysis tools, it has become possible to measure brain volume changes up to around 0.5%. Besides long-term brain changes caused by atrophy in aging or neurodegenerative disease, short-term mechanisms that influence brain volume may exist. When we focus on short-term changes of the brain, changes may be either physiological or pathological. As such determining the cause of volumetric dynamics of the brain is essential. Additionally for an accurate interpretation of longitudinal brain volume measures by means of neurodegeneration, knowledge about the short-term changes is needed. Therefore, in this review, we discuss the possible mechanisms influencing brain volumes on a short-term basis and set-out a framework of MRI techniques to be used for volumetric changes as well as the used analysis tools. 3D T₁-weighted images are the images of choice when it comes to MRI of brain volume. These images are excellent to determine brain volume and can be used together with an analysis tool to determine the degree of volume change. Mechanisms that decrease global brain volume are: fluid restriction, evening MRI measurements, corticosteroids, antipsychotics and short-term effects of pathological processes like Alzheimer's disease, hypertension and Diabetes mellitus type II. Mechanisms increasing the brain volume include fluid intake, morning MRI measurements, surgical revascularization and probably medications like anti-inflammatory drugs and anti-hypertensive medication. Exercise was found to have no effect on brain volume on a short-term basis, which may imply that dehydration caused by exercise differs from dehydration by fluid restriction. In the upcoming years, attention should be directed towards studies investigating physiological short-term changes within the light of long-term pathological changes. Ultimately this may lead to a better understanding of the physiological short-term effects of pathological processes and may aid in early detection of these diseases.

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Fluid-restriction, evening MRI, corticosteroids, & antipsychotics decrease volume

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Fluid-intake, morning MRI, surgical revascularization & medications increase volume

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Short-term changes within the light of long-term pathological changes should be investigated

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Short-term changes may introduce bias in longitudinal data

Late-Life Depression, Hippocampal Volumes, and Hypothalamic-Pituitary-Adrenal Axis Regulation: A Systematic Review and Meta-analysis

BACKGROUND

We systematically reviewed and meta-analyzed the association of late-life depression (LLD) with hippocampal volume (HCV) and total brain volume (TBV), and of cortisol levels with HCV, including subgroup analyses of depression characteristics and methodological aspects.

METHODS

We searched PubMed and Embase for original studies that examined the cross-sectional relationship between LLD and HCV or TBV, and 46 studies fulfilled the inclusion criteria. Standardized mean differences (Hedges' g) between LLD and control subjects were calculated from crude or adjusted brain volumes using random effects. Standardized Fisher transformations of the correlations between cortisol levels and HCVs were calculated using random effects.

RESULTS

We included 2702 LLD patients and 11,165 control subjects from 35 studies examining HCV. Relative to control subjects, patients had significantly smaller HCVs (standardized mean difference = -0.32 [95% confidence interval, -0.44 to -0.19]). Subgroup analyses showed that late-onset depression was more strongly associated with HCV than early-onset depression. In addition, effect sizes were larger for case-control studies, studies with lower quality, and studies with small sample size, and were almost absent in cohort studies and studies with larger sample sizes. For TBV, 2523 patients and 7880 control subjects from 31 studies were included. The standardized mean difference in TBV between LLD and control subjects was -0.10 (95% confidence interval, -0.16 to -0.04). Of the 12 studies included, higher levels of cortisol were associated with smaller HCV (correlation = -0.11 [95% confidence interval, -0.18 to -0.04]).

CONCLUSIONS

While an overall measure of LLD may be associated with smaller HCVs, differentiating clinical aspects of LLD and examining methodological issues show that this relationship is not straightforward.

Memory Training Program Decreases the Circulating Level of Cortisol and Pro-inflammatory Cytokines in Healthy Older Adults

Aging cognitive decline has been associated to impairment of the Hypothalamus Pituitary Adrenals (HPA) axis activity and a higher level of the systemic inflammation. However, little is known about the molecules driving this process at peripheral level. In addition, the cognitive function is to some extent modifiable with Memory Training (MT) programs, even among older adults and beyond. The study aims to evaluate whether MT could contribute to ameliorate cognitive performance and modulate the HPA axis activity as well the low level inflammation in the aging phenotype. Whether the phosphatase WIP-1, a negative regulator for inflammation, is involved in this process was also investigated. We recruited 31 young adults (19-28, years of age) and 62 older adults aged over 60. Thirty-two older adults were submitted to 6-months of MT program (EG), and 28 older adults were no treated and used as Control Group (CG). Global cognitive functioning (MMSE score), verbal and visual memory, and attention were assessed at baseline (T0) and after 6-months (T1). At the same time, plasmatic level of Cortisol (C), IL-1β, IL-18, IL-6, and the expression of WIP-1 mRNA and protein in ex vivo Peripheral Blood Mononuclear Cells were analyzed in young adults at T0, as well in older adults at T0 and T1. Together, the results suggest that MT improves the global cognitive functionality, verbal and visual memory, as well as the level of attention. At the same time we observed a decrease of the plasmatic level of C, of the cytokines, and an increase of the expression of mRNA and protein of WIP-1. The analysis of correlations highlighted that the level of the mRNA of WIP-1 was positively associated to the MMSE score, and negatively to the C and cytokine levels. In conclusion, we purpose the MT as tool that could help support successful aging through the improving of memory, attention and global cognitive function performance. Furthermore, this approach could participate to maintain lower the peripheral levels of the C and pro-inflammatory cytokines. The WIP-1 as a potential new target of the pathophysiology of aging is theorized.

Moderating Effects of Cortisol on Neural-Cognitive Association in Cognitively Normal Elderly Subjects

Cortisol homeostasis is important for healthy brain and cognitive aging. The aim of the current study is to investigate the role of serum cortisol levels in the relationship between regional brain volumes and cognitive processing speed in a group of cognitively normal elderly subjects. Forty-one healthy elderly participants were from a parallel longitudinal study. The reported data in this study reflects baseline measurements. Whole-brain anatomical scanning was performed using a 3.0 Tesla Philips Medical Systems Achieva scanner. Cognitive processing speed was assessed by the digit-symbol and symbol search tests, from the Chinese version of the Wechsler Adult Intelligence Scale—third edition (WAIS-III). Serum cortisol levels (sampled in the late morning) were measured by ELISA kits. Whole-brain regression analysis revealed that serum cortisol levels positively predicted the white matter volumes (WMV) of the right thalamus, the gray matter volumes (GMV) of the left thalamus and right cerebellar tonsil, and negatively predicted the WMV and GMV of the left middle temporal gyrus (MTG) in 41 healthy elderly participants. Furthermore, serum cortisol significantly moderated the relationship between the GMV of the left MTG and processing speed, as well as the GMV of the left thalamus and processing speed. This study provided the first piece of evidence supporting serum cortisol levels in moderating the relationship between regional brain volumes and processing speed in healthy elderly subjects. This observation enriches our understanding of the role of cortisol in brain morphology and cognitive functioning.

Associations between hippocampal morphology, diffusion characteristics, and salivary cortisol in older men

High, unabated glucocorticoid (GC) levels are thought to selectively damage certain tissue types. The hippocampus is thought to be particularly susceptible to such effects, and though findings from animal models and human patients provide some support for this hypothesis, evidence for associations between elevated GCs and lower hippocampal volumes in older age (when GC levels are at greater risk of dysregulation) is inconclusive. To address the possibility that the effects of GCs in non-pathological ageing may be too subtle for gross volumetry to reliably detect, we analyse associations between salivary cortisol (diurnal and reactive measures), hippocampal morphology and diffusion characteristics in 88 males, aged ∼73 years. However, our results provide only weak support for this hypothesis. Though nominally significant peaks in morphology were found in both hippocampi across all salivary cortisol measures (standardised β magnitudes<0.518, p_uncorrected>0.0000003), associations were both positive and negative, and none survived false discovery rate correction. We found one single significant association (out of 12 comparisons) between a general measure of hippocampal diffusion and reactive cortisol slope (β=0.290, p=0.008) which appeared to be driven predominantly by mean diffusivity but did not survive correction for multiple testing. The current data therefore do not clearly support the hypothesis that elevated cortisol levels are associated with subtle variations in hippocampal shape or microstructure in non-pathological older age.

Personality, Cortisol, and Cognition in Non-demented Elderly Subjects: Results from a Population-Based Study

Certain personality traits, in particular higher neuroticism, have been associated, on one hand, with elevated cortisol levels, and on the other hand, with poorer cognitive performance. At the same time, several studies highlighted the association between high cortisol and poor cognitive functioning. Here, we hypothesized that increased cortisol may be associated with poorer cognition and with certain personality traits (mainly high neuroticism), and that personality might explain the association between cortisol and cognition. A cross-sectional analysis was conducted using data from Colaus/PsyColaus, a population-based study involving residents of Lausanne, Switzerland. Salivary cortisol samples (upon waking, 30 min after waking, at 11 am and at 8 pm) along with cognitive and personality measures were obtained from 643 non-demented participants aged at least 65. Personality traits were assessed using the NEO Five-Factor Inventory (NEO-FFI). We examined the links between the cortisol Area under the Curve (AUC), the Clinical Dementia Rating Sum of Boxes (CDRSOB) and the NEO-FFI scores. No association was found between personality traits and the CDRSOB or the MMSE score, controlling for age, sex, depression, education and BMI. However, the executive functioning domain z-score was negatively associated with agreeableness (p = 0.005; slope = -0.107 [-0.181; -0.033]) and openness (p = 0.029; slope = -0.081 [-0.154; -0.008]) after controlling for age, sex, depression, education and BMI. The CDRSOB score was positively associated with the cortisol AUC after controlling for age, sex, BMI, education and depression, (p = 0.003; slope = 0.686 [0.240; 1.333]). This association remained significant after controlling for personality traits and for the interaction between personality traits and the cortisol AUC (p = 0.006; slope = 0.792 [0.233; 1.352]. High agreeableness and openness might be associated with poorer executive performance in later life. Increased cortisol may be associated with both specific personality traits (high extraversion, low openness) and worse cognitive performance. Increased salivary cortisol does not mediate the relationship between personality traits and cognitive impairment.

Plasma Cortisol, Brain Amyloid-β, and Cognitive Decline in Preclinical Alzheimer's Disease: A 6-Year Prospective Cohort Study

BACKGROUND

Hypothalamic-pituitary-adrenal axis dysregulation, which is typically assessed by measuring cortisol levels, is associated with cognitive dysfunction, hippocampal atrophy, and increased risk for mild cognitive impairment and Alzheimer's disease (AD). However, little is known about the role of hypothalamic-pituitary-adrenal axis dysregulation in moderating the effect of high levels of amyloid-β (Aβ+) on cognitive decline in the preclinical phase of AD, which is often protracted, and thus offers opportunities for prevention and early intervention.

METHODS

Using data from a 6-year multicenter prospective cohort study, we evaluated the relation between Aβ level, plasma cortisol level, and cognitive decline in 416 cognitively normal older adults.

RESULTS

Results revealed that Aβ+ older adults experienced faster decline than Aβ- older adults in all cognitive domains (Cohen's d at 6-year assessment = 0.37-0.65). They further indicated a significant interaction between Aβ and cortisol levels for global cognition (d = 0.32), episodic memory (d = 0.50), and executive function (d = 0.59) scores, with Aβ+ older adults with high cortisol levels having significantly faster decline in these domains compared with Aβ+ older adults with low cortisol levels. These effects were independent of age, sex, APOE genotype, anxiety symptoms, and radiotracer type.

CONCLUSIONS

In cognitively healthy older adults, Aβ+ is associated with greater cognitive decline and high plasma cortisol levels may accelerate the effect of Aβ+ on decline in global cognition, episodic memory, and executive function. These results suggest that therapies targeted toward lowering plasma cortisol and Aβ levels may be helpful in mitigating cognitive decline in the preclinical phase of AD.