Morning salivary cortisol and cognitive function in mid-life: evidence from a population-based birth cohort

Association of perceived stress with memory decline in older Chinese: The Guangzhou Biobank Cohort Study

BACKGROUND

Previous studies on associations of perceived stress with poor memory performance in older adults showed inconsistent results. We examined the prospective associations of perceived stress with memory decline using data from Guangzhou Biobank Cohort Study (GBCS).

METHODS

Perceived stress was measured by the Perceived Stress Scale (PSS) at baseline (2003-2006), with greater scores indicating greater stress. Memory function was measured by delayed 10-word recall test (DWRT) and immediate 10-word recall test (IWRT), with greater scores indicating better performance, at baseline and follow-up (2008-2012) examinations, analyzed as mean annual change in scores.

RESULTS

9656 participants (72 % women) with mean age 61.6 (standard deviation = 6.4) years were included. During an average of 4.4 years of follow-up, after adjusting for confounders, each one-point greater PSS score was associated with mean annual decline in DWRT scores (β (95 % CI) = -0.005 (-0.008 to -0.002)). Greater Perceived Helplessness (PH) scores, but not Perceived Self-efficacy scores, was associated with greater mean annual decline in DWRT and IWRT scores (β (95 % CI) = -0.005 (-0.009 to -0.001) and - 0.012 (-0.018 to -0.005), respectively), and similar patterns were observed in five out of seven PH items (βs from -0.02 to -0.07). Interaction analysis showed that the association of greater PSS with greater decline in DWRT scores was observed only in those with low family income (β (95 % CI) = -0.08 (-0.13 to -0.04), P for interaction = 0.03).

CONCLUSIONS

Greater perceived stress was associated with a greater decline in delayed recall memory, especially in those with low family income.

Pet ownership and cognitive frailty among Chinese rural older adults who experienced a social loss: Is there a sex difference?

BACKGROUND

The loss of a spouse (widowed or divorced) is one of the most common forms of social loss in older adults. However, evidence is limited regarding whether social loss is associated with cognitive frailty. Maintaining pets has become increasingly popular. Despite its health benefits, little is known about whether pet ownership can buffer cognitive frailty in older adults facing social loss. Here, we examined the role of pet ownership in the relationship between social loss and cognitive frailty among males and females older adults living in rural China.

METHODS

A total of 2638 rural older adults were analysed. Binary logistic regression analyses were conducted to explore risk or protective factors associated with cognitive frailty. Participants were categorised into four groups according to social loss and pet ownership assessment: (i) no social loss + own pet, (ii) no social loss + no pet, (iii) social loss + own pet, and (iv) social loss + no pet. Binary logistic regression was also performed to examine the interaction effects of social loss and pet ownership on cognitive frailty stratified by sex.

RESULTS

Regardless of pet ownership, spousal loss was associated with cognitive frailty for men and women. Female participants who experienced loss without a pet had a significantly higher risk of cognitive frailty. However, we did not observe a significant association between pet ownership and cognitive frailty among men who experienced loss.

CONCLUSIONS

Our findings highlight the buffering effect of pet ownership on cognitive frailty in older women experiencing social loss. This implies that targeted support for older adults of different sexes who experienced social losses may be effective in preventing cognitive frailty in rural China.

Widowhood and cognitive decline in adults aged 50 and over: A systematic review and meta-analysis

While widowhood is known to be associated with poorer physical and mental health outcomes, studies examining the association of widowhood with cognition have yielded mixed results. This review aimed to elucidate the link between widowhood and cognitive decline. A systematic search of Medline, Embase, PsycInfo, CINAHL and Scopus (until December 2020) was conducted to identify studies on the association between widowhood (vs. being married) and cognition in cognitively healthy adults aged 50 +. A cross-sectional meta-analysis (of 10 studies; n = 24,668) found a significant association of widowhood with cognition (g = - 0.36, 95% CI [- 0.47, - 0.25], p = < 0.001). Meta-regressions suggested that study design, cognitive domain measured, sample age, difference in mean age between widowed and married groups, and study continent did not account for observed heterogeneity. A longitudinal meta-analysis (of 3 studies; n = 10,378) found that the "continually widowed" group (from baseline to follow-up) showed significantly steeper declines in cognition compared to the "continually married" group (g = - 0.15, 95%CI [- 0.19, - 0.10], p = < 0.001). Findings indicate that widowhood may be a risk factor for cognitive decline. As there are no effective treatments for cognitive impairment, studying mechanisms by which widowhood might be associated with poorer cognition could inform prevention programs for those who have experienced spousal bereavement.

Salivary biomarkers and neuropsychological outcomes: A non-invasive approach to investigate pollutants-associated neurotoxicity and its effects on cognition in vulnerable populations

The occurrence of neurotoxicity caused by xenobiotics such as pesticides (dichlorodiphenyltrichloroethane, organophosphates, pyrethroids, etc.) or metals (mercury, lead, aluminum, arsenic, etc.) is a growing concern around the world, particularly in vulnerable populations with difficulties on both detection and symptoms treatment, due to low economic status, remote access, poor infrastructure, and low educational level, among others features. Despite the numerous molecular markers and questionnaires/clinical evaluations, studying neurotoxicity and its effects on cognition in these populations faces problems with samples collection and processing, and information accuracy. Assessing cognitive changes caused by neurotoxicity, especially those that are subtle in the initial stages, is fundamentally challenging. Finding accurate, non-invasive, and low-cost strategies to detect the first signals of brain injury has the potential to support an accelerated development of the research with these populations. Saliva emerges as an ideal pool of biomarkers (with interleukins and neural damage-related proteins, among others) and potential alternative diagnostic fluid to molecularly investigate neurotoxicity. As a source of numerous neurological biomarkers, saliva has several advantages compared to blood, such as easier storage, requires less manipulation, and the procedure is cheaper, safer and well accepted by patients compared with drawing blood. Regarding cognitive dysfunction, neuropsychological batteries represent, with their friendly interface, a feasible and accurate method to evaluate the eventual cognitive deficits associated with neurotoxicity in people from diverse cultural and educational backgrounds. The association of these two tools, saliva and neuropsychological batteries, to cover the molecular and cognitive aspects of neurotoxicity in vulnerable populations, could potentially increase the prevalence of early intervention and successful treatment.

Sleep and circadian rhythm disturbances in intensive care unit (ICU)-acquired delirium: a case-control study

OBJECTIVE

The relationships among sleep, circadian rhythm, and intensive care unit (ICU)-acquired delirium are complex and remain unclear. This study aimed to examine the pathophysiological mechanisms of sleep and circadian rhythm disturbances in patients with ICU-acquired delirium.

METHODS

This study included critical adult patients aged 18 to 75 years who were treated in the ICU. Twenty-four-hour polysomnography was performed and serum melatonin and cortisol levels were measured six times during polysomnography. Receiver operating characteristic curves and binomial logistic regression were used to evaluate the potential of sleep, melatonin, and cortisol as indicators of delirium in the ICU.

RESULTS

Patients with delirium (n = 24) showed less rapid eye movement (REM) sleep compared with patients without delirium (n = 24, controls). Melatonin levels were lower and cortisol levels were higher in the delirium group than in the control group. REM sleep, melatonin, and cortisol were significantly associated with delirium. The optimal cutoff values of REM sleep and mean melatonin and cortisol levels that predicted delirium were ≤1.05%, ≤422.09 pg/mL, and ≥212.14 ng/mL, respectively.

CONCLUSIONS

REM sleep, and melatonin and cortisol levels are significantly associated with the risk of ICU-acquired delirium. Improved sleep and readjustment of circadian rhythmicity may be therapeutic targets of ICU-acquired delirium.

Glucocorticoid Therapy is Associated with a Lower Risk of Dementia

BACKGROUND

Recent evidence indicates an important role for neuroinflammation in the pathological cascade of Alzheimer's disease (AD), and neuroinflammation is increasingly being recognized as a potential therapeutic target.

OBJECTIVE

To assess the impact of glucocorticoids on the risk of developing dementia.

METHODS

We used health insurance data of the largest German health insurer from 2004-2013 with a baseline sample of 176,485 persons aged 50 years and older to study the association of glucocorticoid treatment and incidence of dementia. Cox proportional-hazard models were calculated adjusting for sex, age, and comorbidities known to be major risk factors for dementia and were given as hazard ratios (HR) with 95% confidence intervals (CI). We further stratified glucocorticoid treatment by route of application and treatment duration.

RESULTS

Of the 176,485 dementia-free persons, 19,938 were diagnosed with dementia by the end of 2013. The risk of suffering from dementia was significantly lower for glucocorticoid users compared to non-users (HR = 0.81, CI = 0.78-0.84). The lowest risk was found among users of inhaled glucocorticoid (HR = 0.65, CI = 0.57-0.75), followed by nasal (HR = 0.76, CI = 0.66-0.87), other (HR = 0.84, CI = 0.80-0.88), and oral users (HR = 0.83, CI = 0.78-0.88). We found no difference in risk reduction between long- and short-term-users.

CONCLUSION

Longitudinal German health insurance data indicate that the use of glucocorticoids is associated with a lower risk of dementia. Prospective clinical trials will be necessary to determine whether glucocorticoids can have a positive impact on neuroinflammation and thus protect persons against dementia.

Normalized Cortisol Reactivity Predicts Future Neuropsychological Functioning in Children With Mild/Moderate Asthma

Cortisol reactivity to adrenocorticotropic hormone (ACTH) has been associated with neuropsychological processes including attention and memory in children with asthma. While cortisol reactivity to a psychological stressor is often considered a measure of current neuroendocrine functioning, this study examines the association of the cortisol reactivity and subsequent neuropsychological functioning. Using prospective data from the Childhood Asthma Management Program (CAMP), we explored the predictive ability of cortisol reactivity to ACTH and children's later attention and memory using traditional and an alternative cortisol reactivity (normalized cortisol) measures. Cortisol reactivity was assessed at study entry and 1-year follow-up, and neuropsychological functioning was assessed at 3-year follow-up. Cortisol reactivity was assessed through plasma cortisol concentrations collected at baseline (CORTBASELINE) and 30 min post-ACTH challenge (CORTPOST-A CTH). An alternative measure of cortisol reactivity was developed through post-ACTH stimulation cortisol, normalized by cortisol by baseline (CORTNORM -ACTH). CORT B ASELINE positively predicted year 3 attention, while CORTNORM -ACTH negatively predicted attention, suggesting convergence of cortisol variables in prediction of neuropsychological function. Year 1 CORTACTH positively predicted child memory at year 3; Year 1 CORTNORM-ACTH negatively predicted year 3 sustained attentions. These findings demonstrate that HPA reactivity, including the application of normalized cortisol reactivity, can predict subsequent neuropsychological functioning of children with mild to moderate asthma.

Does widowhood affect cognitive function among Chinese older adults?

There is growing evidence from Western countries that widowhood may affect cognitive health in later life. However, little is known about whether widowhood is associated with cognitive health in Eastern Asian countries such as China and what factors may explain the association between widowhood and cognitive health. We add to this line of research by investigating the effect of widowhood on 2-year change in cognitive function among Chinese adults ages 55 and older from 2011 to 2013, using data from the China Health and Retirement Longitudinal Study. Cognitive function was measured by episodic memory and mental intactness (i.e., attention and time orientation). Our results showed that Chinese older adults who were continually widowed at both waves had significantly lower episodic memory scores at Wave 2 than their continually married counterparts, controlling for episodic memory at Wave 1, age, gender, education, and other sociodemographic variables. This suggests that the continually widowed experienced greater decline in episodic memory than the continually married over the 2-year period. After further controlling for economic resources, health, and social engagement, the difference in memory decline between the continually widowed and the continually married barely changed. The effect of widowhood on memory decline was similar for men and women. However, the continually widowed were not significantly different from the continually married in the decline of mental intactness. In addition, newly widowed adults were not significantly different from the continually married in the change of episodic memory and mental intactness. We conclude that staying widowed for 2 years or more may be an independent risk factor for episodic memory decline in China. More research is needed to investigate the mediating and moderating mechanisms underlying the association between widowhood and memory decline.

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.

A reliable global cognitive decline and cortisol as an associated risk factor for patients with late-life depression in the short term: A 1-year prospective study

BACKGROUND

Late-life depression is a risk factor of dementia. It may increase the risk of reliable cognitive decline in the short term, and its associated risk factors remain unclear. Cortisol level may be one of the important predictors.

OBJECTIVES

To estimate whether patients with late-life depression are at an increased risk for reliable global cognitive declines in 1 year, and explore associated risk factors predicting cognitive declines.

METHODS

This prospective 1-year follow-up study involved 148 participants (67 with late-life depression and 81 normal elderly). Global cognitive function was assessed by the Mini-Mental State Examination (MMSE). The reliable global cognitive decline was defined by the reliable change index (RCI) of the MMSE. Factors related to cognitive function (e.g., age, gender, education, duration of depression and severity of depression) were obtained. Serum cortisol levels were measured at baseline.

RESULTS

At the 1-year follow-up assessment, 19 patients with late-life depression (28.4%) showed reliable global cognitive declines, a risk that was 6.4 times (95% CIs = 1.3-31.1, p = 0.021) higher than that of normal elderly. Elevated serum cortisol levels and older age were associated with the risk of cognitive decline that was 1.6- and 1.2-times higher (95% CIs = 1.07-2.5, p = 0.02, and 95% CIs = 1.04-1.4, p = 0.01 respectively).

LIMITATIONS

Serum cortisol levels were measured only in the morning.

CONCLUSIONS

Late-life depression is associated with a greatly increased risk of reliable cognitive decline in short term. Cortisol dysregulation may contribute to the pathology of cognitive decline.

Interactive effects of testosterone and cortisol on hippocampal volume and episodic memory in middle-aged men

Animal and human research suggests that testosterone is associated with hippocampal structure and function. Studies examining the association between testosterone and either hippocampal structure or hippocampal-mediated cognitive processes have overwhelmingly focused on the effects of testosterone alone, without considering the interaction of other neuroendocrine factors. The aim of the present study was to examine the interactive effects of testosterone and cortisol in relation to hippocampal volume and episodic memory in a sample of late-middle aged men from the Vietnam Era Twin Study of Aging. The average age of participants was 56.3 years (range 51-60). Salivary hormone samples were collected at multiple time-points on two non-consecutive at-home days, and an in-lab assessment. Area under the curve with respect to ground measures for cortisol and testosterone were utilized. Significant testosterone-by-cortisol interactions were observed for hippocampal volume, and episodic memory. When cortisol levels were elevated (1 SD above the mean), testosterone levels were positively associated with hippocampal volume and memory performance. However, when cortisol levels were low (1 SD below the mean), testosterone levels were inversely related to hippocampal volume and memory performance. These findings suggest that in context of high cortisol levels, testosterone may be neuroprotective. In contrast, low testosterone may also be neuroprotective in the context of low cortisol levels. To our knowledge this is the first demonstration of such an interaction in a structural brain measure and an associated cognitive ability. These results argue in favor of broadening neuroendocrine research to consider the simultaneous and interactive effects of multiple hormones on brain structure and function.

Hair cortisol and cognitive performance in working age adults

It has been hypothesized that prolonged exposure to high cortisol levels results in cognitive impairment. However, previous research into the relationship between cortisol and cognition has produced mixed results, most likely due to difficulties achieving valid estimates of long-term cortisol exposure based on salivary or plasma cortisol assessments at a single time point. Furthermore, there has been little research on the cognitive effects of long-term cortisol exposure in working-age adults. In the present study, hair samples were collected from 246 nurses (89.8% female) aged from 21 to 62 (M=42.0, SD=11.2). Hair cortisol concentrations (HCC) in the proximal 3-cm hair segment were analyzed providing an estimate of integrated cortisol secretion over the 3 month-period prior to hair sampling. Cognition was measured using a battery of 15 neuropsychological tests, measuring core dimensions of memory, inductive reasoning, processing speed, crystalized intelligence and major aspects of executive functioning. HCC was not significantly related to any of the cognitive abilities measured, either before or after controlling for potential moderators such as age, sex, education, health, well-being, work ability and burnout. Tests for nonlinear relationships also yielded non-significant results. Thus, despite the study being well powered, long term cortisol exposure did not appear to be related to cognitive performance in this sample of working-age adults, suggesting that long term cortisol exposure may be less relevant to cognition in younger and middle-aged adults than was previously thought.

Prisoner of war status, posttraumatic stress disorder, and dementia in older veterans

BACKGROUND

It is not known whether prisoners of war (POWs) are more likely to develop dementia independently of the effects of posttraumatic stress disorder (PTSD).

METHODS

We performed a retrospective cohort study in 182,879 U.S. veterans age 55 years and older, and examined associations between POW status and PTSD at baseline (October 1, 2000-September 30, 2003), and incident dementia during follow-up (October 1, 2003-September 30, 2012).

RESULTS

A total of 484 veterans (0.3%) reported being POWs, of whom 150 (31.0%) also had PTSD. After adjusting for demographics, medical and psychiatric comorbidities, period of service, and the competing risk of death, the risk of dementia was increased in veterans who were POWs only (hazard ratio [HR], 1.61; 95% confidence interval [CI], 1.30-1.98) or had PTSD only (HR, 1.52; 95% CI, 1.41-1.64) and was greatest in veterans who were POWs and also had PTSD (HR, 2.24; 95% CI, 1.72-2.92).

CONCLUSIONS

POW status and PTSD increase risk of dementia in an independent, additive manner in older veterans.

Lower morning to evening cortisol ratio is associated with cognitive impairment in men but not women: An analysis of 733 older subjects of the cross-sectional KORA-Age study

BACKGROUND

A dysregulated hypothalamic-pituitary-adrenocortical axis (HPA) is thought to play a role in the pathophysiology of cognitive impairment. Surprisingly, little agreement exists on the association of cortisol and cognitive impairment. Thus, we sought to examine the association between cognitive function and salivary cortisol levels in a representative sample of older men and women.

METHODS

A cross-sectional analysis was conducted among 733 study participants (65-90 years old, mean age=74.9) of the population-based KORA (Cooperative Health Research in the Region of Augsburg)-Age study. Associations were examined between cognitive function (determined by telephone interview for cognitive status-modified, TICS-m) and salivary cortisol measured upon waking (M1), 30min after awakening (M2), and in the late evening (E).

RESULTS

In a dose response manner, lower morning (M1 and M2), and increased evening levels were observed in participants with probable dementia (4.5%, N=33) and slightly increased in those with mild cognitive impairment (MCI) (13.8%, N=101) compared to healthy individuals. Higher morning to evening ratios were associated with reduced odds of cognitive impairment, even after adjustments for important confounders (M1/E ratio: OR=1.50, 95% CI=1.08-2.07, M2/E ratio: 1.41, 1.01-1.95, per 1 standard deviation (SD) increase). However, the significant association of an increased risk for cognitive impairment was observed among men (M1/E: OR=1.94, 95% CI=1.24-3.02; M2/E=1.74, 1.12-2.71) but not women (M1/E: OR=1.11, 0.69-1.78; M2/E=1.09, 0.67-1.77).

CONCLUSION

Our findings suggest that dysregulated HPA axis reactivity, evidenced by blunted diurnal cortisol responses, are associated with impaired cognitive function in an aged population.

Antenatal glucocorticoids: where are we after forty years?

Since their introduction more than forty years ago, antenatal glucocorticoids have become a cornerstone in the management of preterm birth and have been responsible for substantial reductions in neonatal mortality and morbidity. Clinical trials conducted over the past decade have shown that these benefits may be increased further through administration of repeat doses of antenatal glucocorticoids in women at ongoing risk of preterm and in those undergoing elective cesarean at term. At the same time, a growing body of experimental animal evidence and observational data in humans has linked fetal overexposure to maternal glucocorticoids with increased risk of cardiovascular, metabolic and other disorders in later life. Despite these concerns, and somewhat surprisingly, there has been little evidence to date from randomized trials of longer-term harm from clinical doses of synthetic glucocorticoids. However, with wider clinical application of antenatal glucocorticoid therapy there has been greater need to consider the potential for later adverse effects. This paper reviews current evidence for the short- and long-term health effects of antenatal glucocorticoids and discusses the apparent discrepancy between data from randomized clinical trials and other studies.

Cortisol and cognitive function in midlife: the role of childhood cognition and educational attainment

Adult cognition and age-related cognitive decline can be influenced by dysregulation of the hypothalamic pituitary adrenal axis with concomitant changes in cortisol levels. However, very little is known about the role of childhood cognition and educational attainment in this relationship. Using data from the British 1946 birth cohort, the present study investigated: (1) associations between cortisol levels and patterns and cognitive function in midlife; (2) direct and interactive effects of childhood cognition, educational attainment and cortisol on cognitive function in midlife. Verbal memory, letter search speed and reaction time were assessed at age 60-64 years. Salivary cortisol samples (wakening, 30 min after wakening and evening) were collected at the same age. Childhood cognitive ability was measured at ages 8, 11, and 15, and educational level was reported at age 26. Associations between cortisol, childhood cognition, educational attainment and cognitive function in midlife were tested using linear regression and structural equation modelling approaches. Higher evening cortisol level was associated with slower reaction time and lower verbal memory. These associations were independent of childhood cognition and education as well as a range of other potential confounders. Childhood cognition and education were not directly associated with evening cortisol. However, there was a significant interaction effect between childhood cognition and evening cortisol on reaction time (p=.002): higher evening cortisol was associated with slower reaction time only among those with low childhood cognitive ability. There was little evidence of associations between the other cortisol measures and cognitive function.

Prospective association of morning salivary cortisol with depressive symptoms in mid-life: a life-course study

OBJECTIVE

Associations of cortisol and depression vary at different life-stages, yet population-based, prospective studies are scarce. We aimed to assess associations of morning cortisol with depressive symptoms in mid-life taking account of lifetime psychological health.

METHODS

Participants were 5,403 men and women from the 1958 British Birth Cohort whose salivary cortisol was assessed at 45y (45min after waking (T1) and 3h later (T2)) and who completed the 5-item Mental-Health Index (MHI-5) about depressive symptoms at age 50y. Lifetime psychological health was identified from child and adult measures.

RESULTS

For women, higher T2 cortisol at 45y predicted depression (MHI-5 scores ≤52) at 50y (odds ratio [OR]=1.17; 95% confidence intervals [CI] 1.05,1.30 per standard deviation increase in T2 cortisol), attenuating when adjusted for current (45y) and previous (7-42y) psychological health (OR=1.11; 95% CI 0.98, 1.24). Similarly, an association in women of flatter cortisol delta (T2-T1) with depressive symptoms at 50y weakened after adjustment for current (45y) and previous (7-42y) psychological health. For men, lower T2 cortisol at 45y predicted greater depressive symptoms at 50y and the association strengthened when adjusted for lifetime psychological health. Likewise, lower cortisol AUC predicted higher risk of depression for men after adjusting for prior psychological health (OR=0.85; CI 0.72, 1.00). Associations were largely unaltered by control for covariates.

CONCLUSIONS

In women, higher cortisol in late morning at 45y is prospectively associated with depressive symptoms at 50y through a link with lifetime psychological health. In men, lower cortisol predicts subsequent symptoms, independent of depressive history.

Causes and consequences of age-related steroid hormone changes: insights gained from nonhuman primates

Similar to humans, rhesus macaques (Macaca mulatta) are large, long-lived diurnal primates, and show similar age-related changes in the secretion of many steroid hormones, including oestradiol, testosterone, cortisol and dehydroepiandrosterone (DHEA). Consequently, they represent a pragmatic animal model in which to examine the mechanisms by which these steroidal changes contribute to perturbed sleep-wake cycles and cognitive decline in the elderly. Using remote serial blood sampling, we have found the circulating levels of DHEA sulphate, as well as oestradiol and testosterone, decline markedly in old monkeys. Furthermore, using the real-time polymerase chain reaction, we have shown that the genes for the enzymes associated with the conversion of DHEA to oestradiol and testosterone (3β-hydroxysteroid dehydrogenase, 17β-hydroxysteroid dehydrogenase, and aromatase) are highly expressed in brain areas associated with cognition and behaviour, including the hippocampus, prefrontal cortex and amygdala. Taken together, these findings suggest that the administration of supplementary DHEA in the elderly may have therapeutic potential for cognitive and behavioural disorders, although with fewer negative side effects outside of the central nervous system. To test this, we have developed a novel steroid supplementation paradigm for use in old animals; this involves the oral administration of DHEA and testosterone at physiologically relevant times of the day to mimic the circadian hormone patterns observed in young adults. We are currently evaluating the efficacy of this steroid supplementation paradigm with respect to reversing age-associated disorders, including perturbed sleep-wake cycles and cognitive decline, as well as an impaired immune response.

25-Hydroxyvitamin D and cognitive performance in mid-life

Hypovitaminosis D has been linked with poor cognitive function, particularly in older adults, but studies lack a lifespan approach; hence, the effects of reverse causality remain unknown. In the present study, we aimed to assess the relationship between 25-hydroxyvitamin D (25(OH)D) concentrations and subsequent cognitive performance in mid-adulthood and the influence of earlier life factors, including childhood cognitive ability, on this association. Information for the present study was obtained from the members of the 1958 British birth cohort (n 6496). Serum 25(OH)D concentration, indicating vitamin D status, was measured at age 45 years. Verbal memory (immediate and delayed word recall), verbal fluency (animal naming) and speed of processing were tested at age 50 years. Information on childhood cognitive ability, educational attainment, vitamin D-related behaviours and other covariates was collected prospectively from participants throughout their life. Childhood cognitive ability and educational attainment by age 42 years were strongly correlated with cognitive performance at age 50 years and with several vitamin D-related behaviours in mid-adulthood, but not with 25(OH)D concentrations at age 45 years. Participants with both low ( < 25 nmol/l) and high ( ≥ 75 nmol/l) 25(OH)D concentrations at age 45 years performed significantly worse on immediate word recall. The associations attenuated after adjustment for childhood cognitive ability, education, and socio-economic position; however, for the immediate word recall test, there was a non-linear association with 25(OH)D after further adjustment for obesity, menopausal status, smoking, alcohol consumption, physical activity and depressive symptoms at age 45 years (Pcurvature= 0·01). The present study demonstrated that 25(OH)D concentrations were non-linearly associated with immediate word recall in mid-life. A clarification of the level of 25(OH)D concentrations that is most beneficial for predicting better cognitive performance in mid-life is required.