Are optimal levels of testosterone associated with better cognitive function in healthy older women and men?

Sex steroid and cognitive function among community-dwelling older men with or without vascular risk factors: a cross-sectional study

BACKGROUND

The relationship of testosterone and estradiol concentrations with cognitive function among community-dwelling older men was inconclusive. To examine the association of serum testosterone and estradiol concentrations with cognitive function in older men with or without vascular risk factors (VRFs).

METHODS

This cross-sectional study consisted of 224 community-dwelling men aged 65-90 years in the Songjiang District of Shanghai, China. Serum testosterone and estradiol were measured by electrochemiluminescence immunoassay. The following five factors were defined as VRFs in this study: obesity, history of hypertension, diabetes, stroke, and coronary heart disease. Multivariable linear regression was used to examine the association of testosterone and estradiol with the Mini-Mental State Examination (MMSE) in participants with or without VRF. Restricted cubic spline (RCS) regression was performed to account for the nonlinearity of these associations.

RESULTS

An inverted "U" shaped non-linear relationship was found between testosterone concentration and MMSE score in men with one VRF (P overall =.003, non-linear P =.002). Estradiol showed an inverted "U" shaped non-linear relationship with MMSE score independent of VRFs (men without VRF, P overall =.049, non-linear P =.015; men with one VRF, overall P =.007, non-linear P =.003; men with two or more VRFs, overall P =.009, non-linear P =.005).

CONCLUSION

In older men, an optimal level of sex steroid concentration may be beneficial to cognitive function and the VRFs should be considered when interpreting the relationship between sex steroid and cognitive function.

Sex Differences in Dementia, Cognition, and Health in the Cognitive Function and Ageing Studies (CFAS)

Background

There is renewed interest in whether sex differences in dementia risk exist, and what influence social and biological factors have.

Objective

To review evidence from the Cognitive Function and Ageing Studies (CFAS), a multi-center population-representative cohort study in the UK; focusing on dementia and cognition, incorporating findings on participants' health and social circumstances.

Methods

After identifying all CFAS publications, the results of all sex-stratified primary analyses of CFAS data were narratively reviewed.

Results

Of 337 publications, 94 report results by sex (including null findings), which are summarized by theme: dementia epidemiology, cognition, mental health, health expectancy, social context and biological resource (including neuropathology).

Conclusions

Where differences are found they most commonly favor men; however, greater mortality in men may confound associations with age-related outcomes. This 'survival bias' may explain findings of greater risk of dementia and faster cognitive decline in women. Age-specific dementia incidence was similar between sexes, although reduced incidence across study generations was more pronounced in men. Mood disorders were more prevalent in women, but adjusting for disability and deprivation attenuated the association. Prominent findings from other cohorts that women have more Alzheimer's disease pathology and greater risk of dementia from the Apolipoprotein E ɛ4 allele were not observed, warranting further investigation. The 'male-female health-survival paradox' is demonstrated whereby women live longer but with more comorbidity and disability. Examining why health expectancies changed differently over two decades for each sex (interacting with deprivation) may inform population interventions to improve cognitive, mental and physical health in later life.

Sex-based differences in effector cells of the adaptive immune system during Alzheimer's disease and related dementias

Neurological conditions such as Alzheimer's disease (AD) and related dementias (ADRD) present with many challenges due to the heterogeneity of the related disease(s), making it difficult to develop effective treatments. Additionally, the progression of ADRD-related pathologies presents differently between men and women. With two-thirds of the population affected with ADRD being women, ADRD has presented itself with a bias toward the female population. However, studies of ADRD generally do not incorporate sex-based differences in investigating the development and progression of the disease, which is detrimental to understanding and treating dementia. Additionally, recent implications for the adaptive immune system in the development of ADRD bring in new factors to be considered as part of the disease, including sex-based differences in immune response(s) during ADRD development. Here, we review the sex-based differences of pathological hallmarks of ADRD presentation and progression, sex-based differences in the adaptive immune system and how it changes with ADRD, and the importance of precision medicine in the development of a more targeted and personalized treatment for this devastating and prevalent neurodegenerative condition.

Sex hormones, SHBG and cognitive performance among older Australian women: an observational study

OBJECTIVE

This study aims to explore the associations between sex hormones and cognitive performance in older women.

METHODS

Associations between sex hormones, sex hormone binding globulin (SHBG) and cognitive performance were examined in women aged at least 70 years, without dementia and not using medications that influence sex hormones. Linear and generalized linear regression models included age, body mass index, education, smoking, alcohol, living circumstances, diabetes, hypertension, depression and impaired renal function.

RESULTS

The included 5511 women had a median (interquartile range) age of 73.9 (71.6-77.6) years. No associations were found for estrone, estradiol, testosterone or dehydroepiandrosterone and cognitive performance. SHBG concentrations above quartile 1 (Q1) were significantly inversely associated with processing speed (Q2, β = -0.94, 95% confidence interval [CI] - 1.64 to -0.24, p = 0.009; Q3, β = -0.82, 95% CI -1.53 to -0.10, p = 0.025; and Q4, β = -0.95, 95% CI -1.70 to -0.20, p = 0.013).

CONCLUSIONS

Sex hormones were not associated with cognitive performance. The finding that low SHBG is associated with better processing speed warrants further investigation. The null findings for the sex hormones establish a firm baseline to confidently explore the association between sex hormones and longitudinal cognitive performance in this population.

TRIAL REGISTRATION

International Standard Randomized Controlled Trial Number Register (ISRCTN83772183) and ClinicalTrials.gov (NCT01038583).

Testosterone, oxytocin and co-operation: A hypothesis for the origin and function of music

Since the time of Darwin, theories have been proposed on the origin and functions of music; however, the subject remains enigmatic. The literature shows that music is closely related to important human behaviours and abilities, namely, cognition, emotion, reward and sociality (co-operation, entrainment, empathy and altruism). Notably, studies have deduced that these behaviours are closely related to testosterone (T) and oxytocin (OXT). The association of music with important human behaviours and neurochemicals is closely related to the understanding of reproductive and social behaviours being unclear. In this paper, we describe the endocrinological functions of human social and musical behaviour and demonstrate its relationship to T and OXT. We then hypothesised that the emergence of music is associated with behavioural adaptations and emerged as humans socialised to ensure survival. Moreover, the proximal factor in the emergence of music is behavioural control (social tolerance) through the regulation of T and OXT, and the ultimate factor is group survival through co-operation. The "survival value" of music has rarely been approached from the perspective of musical behavioural endocrinology. This paper provides a new perspective on the origin and functions of music.

Association between testosterone and cognitive performance in postmenopausal women: a systematic review of observational studies

This review was conducted to explore the association between endogenous testosterone blood concentrations and cognitive performance among community dwelling postmenopausal women. We searched Ovid MEDLINE, EMBASE, PsycINFO and Web of Science databases for observational studies with at least 100 postmenopausal participants. The results were categorized by study design, reporting of total or free testosterone and risk of bias assessments, narratively. Ten of the 26 articles retrieved for full-text review met the inclusion criteria, six provided cross-sectional data, seven provided longitudinal data and one provided case-control data. Cognitive performance tests differed between studies. Eight studies measured testosterone by immunoassay, one by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and one did not specify their methodology. Eleven different cognitive domains were tested by 37 different instruments. Irrespective of the study design, the findings were inconsistent and inconclusive. Both positive and inverse associations were reported for each of global cognition and immediate and delayed verbal recall. The majority of studies reported no association between total or free testosterone and cognitive performance. Although this review did not demonstrate an association between testosterone and cognitive performance in postmenopausal women, the findings should be considered inconclusive due to the imprecision of testosterone measurement and the methodological heterogeneity of the included studies.

Associations between cognitive function and endogenous levels of estradiol and testosterone in adults with type 2 diabetes

AIMS

To assess associations that endogenous estradiol and testosterone levels have with cognitive function in older adults with Type 2 diabetes mellitus (T2DM).

METHODS

We use data from the Look AHEAD clinical trial of behavioral weight loss. Endogenous estradiol and total testosterone levels were determined using stored serum from 996 individuals, mean age 69 years, at two times (averaging 4 years apart) during years 8-18 of follow-up. One to four standardized assessments of attention, executive function, memory, and verbal fluency were collected during this follow-up. Mixed effects models and multiple imputation were used to assess associations that estradiol and total testosterone levels had with body mass index and cognitive function.

RESULTS

Estradiol levels were not associated with cognitive function in either sex. Total testosterone levels were not associated with cognitive function in women, but greater total testosterone levels were associated with better verbal fluency in men (p < 0.001), most strongly among those carrying the APOE-e4 allele (interaction p = 0.02). The weight loss intervention left a legacy of relatively lower cognitive functioning among women, which was not mediated by current levels of sex hormones.

CONCLUSIONS

Behavioral weight loss intervention does not affect cognitive functioning through mechanisms related to estradiol or testosterone.

CLINICALTRIALS

gov Identifier: NCT00017953.

Reproductive hormone levels, androgen receptor CAG repeat length and their longitudinal relationships with decline in cognitive subdomains in men: The European Male Ageing Study

OBJECTIVE

It has been proposed that endogenous sex hormone levels may present a modifiable risk factor for cognitive decline. However, the evidence for effects of sex steroids on cognitive ageing is conflicting. We therefore investigated associations between endogenous hormone levels, androgen receptor CAG repeat length, and cognitive domains including visuoconstructional abilities, visual memory, and processing speed in a large-scale longitudinal study of middle-aged and older men.

METHODS

Men aged 40-79 years from the European Male Ageing Study (EMAS) underwent cognitive assessments and measurements of hormone levels at baseline and follow-up (mean = 4.4 years, SD ± 0.3 years). Hormone levels measured included total and calculated free testosterone and estradiol, dihydrotestosterone, luteinizing hormone, follicle-stimulating hormone, dehydroepiandrosterone sulphate and sex hormone-binding globulin. Cognitive function was assessed using the Rey-Osterrieth Complex Figure Copy and Recall, the Camden Topographical Recognition Memory and the Digit Symbol Substitution Test. Multivariate linear regressions were used to examine associations between baseline and change hormone levels, androgen receptor CAG repeat length, and cognitive decline.

RESULTS

Statistical analyses included 1,827 and 1,423 participants for models investigating relationships of cognition with hormone levels and CAG repeat length, respectively. In age-adjusted models, we found a significant association of higher baseline free testosterone (β=-0.001, p=0.005) and dihydrotestosterone levels (β=-0.065, p=0.003) with greater decline on Rey-Osterrieth Complex Figure Recall over time. However, these effects were no longer significant following adjustment for centre, health, and lifestyle factors. No relationships were observed between any other baseline hormone levels, change in hormone levels, or androgen receptor CAG repeat length with cognitive decline in the measured domains.

CONCLUSIONS

In this large-scale prospective study there was no evidence for an association between endogenous sex hormone levels or CAG repeat length and cognitive ageing in men. These data suggest that sex steroid levels do not affect visuospatial function, visual memory, or processing speed in middle-aged and older men.

Low Serum Testosterone Concentrations Are Associated With Poor Cognitive Performance in Older Men but Not Women

Objective: Current evidence on the association between serum testosterone and cognitive performance has been inconsistent, especially in older adults. To investigate the associations between serum testosterone and cognitive performance in a nationally representative sample of older men and women. Methods: We used data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014. 1,303 men and 1,349 women aged 60 years or older were included in the study. Serum total testosterone was preformed via isotope dilution liquid chromatography tandem mass spectrometry (ID-LC-MS/MS) method. Free testosterone was calculated by Vermeulen's formula. Cognitive performance was evaluated by the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) test, Animal Fluency test, and Digit Symbol Substitution Test (DSST). Binary logistic regression and restricted cubic spline models were applied to evaluate the association of testosterone and cognitive performance. Results: In men, higher concentrations of total testosterone were associated with better performance on CERAD test (OR = 0.51; 95%CI = 0.27-0.95) and DSST (OR = 0.54; 95%CI = 0.30-0.99) in adjusted group. Similarly, higher concentrations of free testosterone were associated with better performance on CERAD test (OR = 0.32; 95%CI = 0.17-0.61) and DSST (OR = 0.41; 95%CI = 0.17-0.96) in men. These associations were not seen in women. Conclusion: Serum testosterone concentrations were inversely associated with cognitive performance in older men but not women in the United States.

Testosterone and Cognitive Impairment or Dementia in Middle-Aged or Aging Males: Causation and Intervention, a Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

To investigate the association between testosterone levels and the risk of dementia and to assess the effectiveness of testosterone supplement treatment in patients with cognitive impairment or dementia.

METHODS

We searched Pubmed, Cochrane Library, and EMBASE on September 30, 2019.

RESULTS

The risk factor portion of the review included 27 studies with 18 599 participants. Studies revealed inconsistent findings on the association between testosterone levels and the risk of all-cause dementia or Alzheimer disease (AD). The result from our meta-analysis showed an increased risk of all-cause dementia with decreasing total testosterone (total-T, 4572 participants, hazard ratio: 1.14, 95% CI: 1.04-1.26). Some studies also found an increased risk of AD with a lower level of total-T, free testosterone, and bioavailable testosterone. Testosterone supplement treatment may improve general cognitive function and motor response in the short term as measured by the Developmental Test of Visual-Motor Integration (mean difference [MD]: 4.4, 95% CI: 1.20-7.59) and the Mini-Mental State Examination (MD: 3.4, 95% CI: 0.83-5.97) and verbal memory as measured by story recall delay at 3 months (MD: 8.4, 95% CI: 0.49-16.3).

CONCLUSION

Lower levels of testosterone may be associated with an increased risk of all-cause dementia or AD. Testosterone supplement treatment may or may not improve general cognitive function in patients with cognitive impairment/AD.

Cognitive impairment and associations with structural brain networks, endocrine status, and risk genotypes in patients with newly diagnosed prostate cancer referred to androgen-deprivation therapy

BACKGROUND

Evidence suggests that patients with prostate cancer (PCPs) receiving androgen-deprivation therapy (ADT) are at risk for cognitive impairment. Research with other populations with cancer indicates that cognitive impairment may also occur before systemic treatment. The authors assessed cognitive impairment in untreated PCPs referred to ADT and explored associations with structural brain networks, endocrine status, and selected genotypes.

METHODS

Forty untreated PCPs and 27 healthy controls (HCs) who completed a questionnaire package underwent neuropsychological testing, magnetic resonance imaging, and blood sampling. Cognitive impairment was defined as a z score ≤-2 on 1 neuropsychological test or ≤-1.5 on 2 neuropsychological tests. Structural brain networks were investigated using diffusion-weighted imaging and graph theory. Associations of cognitive performance with patient-reported outcome measures (PROMs), brain networks, testosterone levels, and genotypes (apolipoprotein ε [APOE], catechol-O-methyltransferase [COMT], and brain-derived neurotrophic factor [BDNF]) were explored.

RESULTS

PCPs performed poorer than HCs on 7 of 15 neuropsychological tests and exhibited a higher frequency of cognitive impairment (57.5% vs 22.2%; P ≤ .01 to .03). All neuropsychological outcomes were associated with ≥1 PROM (P ≤ .01 to .04). Compared with the HC group, the PCP group exhibited altered global network organization as well as disrupted regional network characteristics in frontal and temporal regions (P < .01). PCPs had lower testosterone levels (P < .01) than HCs, which correlated with better visuospatial performance (r = -0.33; P = .04). No effects were found of APOE, COMT, or BDNF.

CONCLUSIONS

The current results suggest that untreated PCPs may demonstrate cognitive impairment and that psychological and behavioral symptoms (PROMs), as well as impairment in structural brain networks, might be the underlying mechanisms.

Blood-based biomarkers in hypothalamic-pituitary axes for the risk of dementia or cognitive decline: a systematic review and meta-analysis

Blood-based biomarkers are ideal candidates for dementia prediction. This systematic review and meta-analysis aimed to evaluate longitudinal relationships of blood hormones and hormone-binding proteins in hypothalamic-pituitary (HP) axes with dementia or cognitive decline. PubMed, MEDLINE, EMBASE, PsycINFO, and BIOSIS were systematically searched from 1919 to June 2020. Fifteen types of hormones and four types of hormone-binding proteins were measured in 48 prospective studies. Increased risk of dementia or cognitive decline could be predicted by elevated blood concentrations of free-thyroxine (free-T4, RR = 1.06, p = 0.001) and sex hormone-binding globulin (SHBG, RR = 1.10, p = 0.025). Lower thyroid-stimulating hormone (TSH) levels within (RR = 1.28, p < 0.001) and below (RR = 1.27, p = 0.004) the normal range were both risky. Current evidence suggests the alterations of multiple blood molecules in HP axes, especially TSH, free-T4, and SHBG precede the incidence of dementia or cognitive decline. The underpinning etiology remains to be elucidated in the future.

Sex differences in Alzheimer's-related Tau biomarkers and a mediating effect of testosterone

Women show greater pathological Tau biomarkers than men along the Alzheimer's disease (AD) continuum, particularly among apolipoprotein ε-E4 (APOE4) carriers; however, the reason for this sex difference in unknown. Sex differences often indicate an underlying role of sex hormones. We examined whether testosterone levels might influence this sex difference and the modifying role of APOE4 status. Analyses included 172 participants (25 cognitively normal, 97 mild cognitive impairment, 50 AD participants) from the Alzheimer's Disease Neuroimaging Initiative (34% female, 54% APOE4 carriers, aged 55-90). We examined the separate and interactive effects of plasma testosterone levels and APOE4 on cerebrospinal fluid phosphorylated-tau181 (p-Tau) levels in the overall sample and the sex difference in p-Tau levels before and after adjusting for testosterone. A significant APOE4-by-testosterone interaction revealed that lower testosterone levels related to higher p-Tau levels among APOE4 carriers regardless of sex. As expected, women had higher p-Tau levels than men among APOE4 carriers only, yet this difference was eliminated upon adjustment for testosterone. Results suggest that testosterone is protective against p-Tau particularly among APOE4 carriers. The lower testosterone levels that typically characterize women may predispose them to pathological Tau, particularly among female APOE4 carriers.

Aging and the Male Reproductive System

This narrative review presents an overview of current knowledge on fertility and reproductive hormone changes in aging men, the factors driving and modulating these changes, their clinical consequences, and the benefits and risks of testosterone (T) therapy. Aging is accompanied by moderate decline of gamete quality and fertility. Population mean levels show a mild total T decline, an SHBG increase, a steeper free T decline, and a moderate LH increase with important contribution of comorbidities (e.g., obesity) to these changes. Sexual symptoms and lower hematocrit are associated with low T and are partly responsive to T therapy. The relationship of serum T with body composition and metabolic health is bidirectional; limited beneficial effects of T therapy on body composition have only marginal effects on metabolic health and physical function. Skeletal changes are associated primarily with estradiol and SHBG. Cognitive decline is not consistently linked to low T and is not improved by T therapy. Although limited evidence links moderate androgen decline with depressive symptoms, T therapy has small beneficial effects on mood, depressive symptoms, and vitality in elderly patients with low T. Suboptimal T (and/or DHT) has been associated with increased risk of stroke, but not of ischemic heart disease, whereas an association with mortality probably reflects that low T is a marker of poor health. Globally, neither severity of clinical consequences attributable to low T nor the nature and magnitude of beneficial treatment effects justify the concept of some broadly applied "T replacement therapy" in older men with low T. Moreover, long-term safety of T therapy is not established.

Debate position: cognition and mood are not improved in men administered exogenous testosterone therapy

PURPOSE OF REVIEW

The purpose of this article is to provide an overview of the increasing evidence suggesting that exogenous testosterone therapy is not associated with improvements in cognition or mood. This article is part of a series, in this issue, in which authors are assigned opinion pieces on controversial topics pertaining to testosterone replacement.

RECENT FINDINGS

Testosterone is increasingly being prescribed. Particularly in the setting of recent data suggestive of possible cardiovascular risk associated with its use; a clear understanding of the domains of health that improve with exogenous testosterone use is important. Data on endogenous and exogenous testosterone with cognition and mood are mixed, likely partly related to methodological differences of type of testosterone, patient population, and dosing.

SUMMARY

Overall, available data are not suggestive of a clear benefit of testosterone supplementation in multiple domains of cognition and in mood. Supraphysiologic testosterone has been associated with adverse psychological outcomes, albeit not uniformly in studies.

Effects of Testosterone Therapy on Cognitive Function in Aging: A Systematic Review

Endogenous testosterone in the aging man has been scrutinized extensively in regard to its effects on performance in many cognitive domains, especially verbal fluency, visuospatial and visuoperceptual abilities, memory, and executive function. Studies of testosterone supplementation have sought to identify potential cognitive improvements in men with and without baseline cognitive impairment, and have had a wide range of results. The variability in outcomes is likely related, in part, to the lack of consensus on methods for testosterone measurement and supplementation and, in part, to the disparate measures of cognitive function used in randomized controlled studies. Despite the limitations imposed by such inconsistent methods, promising associations have been found between cognition and testosterone supplementation in both eugonadal men and men with low testosterone levels, with and without baseline cognitive dysfunction. This systematic review highlights the cognitive measures used in and the outcomes of existing studies of testosterone and cognition in aging men. The review suggests that larger studies and a more standardized approach to assessment will be needed before we can fully understand and realize sustained benefits from testosterone supplementation in the elderly male population, particularly given the substantial increase in testosterone supplementation in clinical practice.

The Effects of Testosterone Supplementation on Cognitive Functioning in Older Men

Reduction in testosterone levels in men during aging is associated with cognitive decline and risk of dementia. Animal studies have shown benefits for testosterone supplementation in improving cognition and reducing Alzheimer’s disease pathology. In a randomized, placebo-controlled, crossover study of men with subjective memory complaint and low testosterone levels, we investigated whether testosterone treatment significantly improved performance on various measures of cognitive functioning. Forty-four men were administered a battery of neuropsychological tests to establish the baseline prior to being randomly divided into two groups. The first group (Group A) received 24 weeks of testosterone treatment (T treatment) followed by 4 weeks washout, and then 24 weeks of placebo (P); the second group (Group B) received the same treatments, in reverse order (Placebo, washout, and then T treatment). In group A (TèP), compared to baseline, there was a modest (1 point) but significant improvement in general cognitive functioning as measured by the Mini Mental State Examination (MMSE) following testosterone treatment. This improvement from baseline was sustained following the washout period and crossover to placebo treatment. Similar Mini Mental State Examination (MMSE) scores were observed when comparing testosterone treatment with placebo. In group B (PèT) a significant increase was observed from baseline following testosterone treatment and a trend towards an increase when compared to placebo treatment. Improvements in baseline depression scores (assessed by Geriatric Depression Scale) were observed following testosterone/placebo treatment in both groups, and no difference was observed when comparing testosterone with placebo treatment. Our findings indicate a modest improvement on global cognition with testosterone treatment. Larger clinical trials with a longer follow- up and with the inclusion of blood and brain imaging markers are now needed to conclusively determine the significance of testosterone treatment.

A Mendelian randomization study of testosterone and cognition in men

Testosterone replacement for older men is increasingly common, with some observations suggesting a protective effect on cognitive function. We examined the association of endogenous testosterone with cognitive function among older men in a Mendelian randomization study using a separate-sample instrumental variable (SSIV) analysis estimator to minimize confounding and reverse causality. A genetic score predicting testosterone was developed in 289 young Chinese men from Hong Kong, based on selected testosterone-related single nucleotide polymorphisms (rs10046, rs1008805 and rs1256031). The association of genetically predicted testosterone with delayed 10-word recall score and Mini-Mental State Examination (MMSE) score was assessed at baseline and follow-up using generalized estimating equation among 4,212 older Chinese men from the Guangzhou Biobank Cohort Study. Predicted testosterone was not associated with delayed 10-word recall score (-0.02 per nmol/L testosterone, 95% confidence interval (CI) -0.06-0.02) or MMSE score (0.06, 95% CI -0.002-0.12). These estimates were similar after additional adjustment for age, education, smoking, use of alcohol, body mass index and the Framingham score. Our findings do not corroborate observed protective effects of testosterone on cognitive function among older men.

The impact of luteinizing hormone and testosterone on beta amyloid (Aβ) accumulation: Animal and human clinical studies

This article is part of a Special Issue "SBN 2014". Hormonal changes associated with ageing have been implicated in the pathogenesis of Alzheimer's disease (AD), the most common form of dementia. Reductions in serum testosterone and increases in luteinizing hormone (LH) are established AD risk factors for dementia in men and have important roles in modulating AD pathogenesis. One of the defining features of AD is the accumulation of amyloid-beta (Aβ) in the brain, which has a key role in the neurodegenerative cascade. Both testosterone and LH have been shown to modulate CNS Aβ accumulation in animal studies, and associations with cerebral amyloid load in human studies have supported this. The underlying mechanisms by which these hormones modulate Aβ accumulation and contribute to neurodegeneration are not completely understood, however they have been shown to regulate Aβ metabolism, enhance its clearance and alter the processing of its parent molecule, the amyloid precursor protein. This review will discuss underlying mechanisms by which testosterone and LH modulate Aβ and provide an update on therapeutic approaches targeting these hormones.

Relationship of serum testosterone levels with cognitive function in chronic antipsychotic-treated male patients with schizophrenia

INTRODUCTION

Some evidence suggests that testosterone might be involved in the cognitive impairments of schizophrenia. We assessed major cognitive domains and serum testosterone levels in male long-term inpatients with schizophrenia. This study aimed to test whether testosterone in serum was abnormal in patients, and whether it was related to the cognitive impairment of schizophrenia.

METHODS

Serum testosterone levels in male schizophrenics (n = 80) and normal controls (n = 40) were measured by immunoassay. All patients were assessed for performance on executive functions, sustaining and focusing of attention, memory functions, and verbal fluency using the Digit Cancellation Test (DCT), Semantic Fluency Test, Spatial Span (SS), Trail Making Test, part A (TMT-A), Block Design, and Paced Auditory Serial Addition Test.

RESULTS

Serum testosterone levels in schizophrenic patients were similar to control subjects (P > 0.05). We found that serum testosterone levels were significantly correlated with total time taken (in seconds) in the DCT (r = 0.261, P < 0.05) and SS score (r = -0.240, P < 0.05) in schizophrenic patients. Moreover, backward linear regression revealed that testosterone levels significantly predicted performance in DCT (β = 0.240, P = 0.028) and SS score (β = -0.207, P = 0.047) in patients.

DISCUSSION

Our findings suggest that there is no significant difference in serum testosterone levels between groups, and that serum testosterone levels are associated with the spatial memory and attention deficits in chronic antipsychotic-treated male patients with schizophrenia.

Endogenous sex hormones and cognitive function in the elderly

BACKGROUND

Estrogen and testosterone may influence cognitive function in the older adult, but the relationship between sex hormones and cognitive function is complex.

AIM

To examine associations of sex hormones and cognitive function among older adults ≥65 years old.

METHODS

Using a cross-sectional research design, data were collected once from 71 elderly (mean age 86.4 years). Global cognitive function and executive function were measured with standardized instruments, and saliva samples were collected for salivary estradiol and testosterone.

RESULTS

Estradiol was significantly and positively correlated with global cognitive function in men only (r = 0.54, p < 0.05). Testosterone was not significantly correlated with global cognitive function or executive function in either gender.

DISCUSSION AND CONCLUSION

Associations between sex hormones and cognitive function were mostly non-significant. However, higher estradiol was significantly correlated with better global cognitive function in men, suggesting gender-specific differences. Along with sex hormones, other comorbidity may need to be assessed together in relation to cognitive function in the elderly. Accordingly, clinicians play an important role in educating and promoting beneficial actions to preserve cognitive function.

Testosterone deficiency, insulin-resistant obesity and cognitive function

Testosterone is an androgenic steroid hormone, which plays an important role in the regulation of male reproduction and behaviors, as well as in the maintenance of insulin sensitivity. Several studies showed that testosterone exerted beneficial effects in brain function, including preventing neuronal cell death, balancing brain oxidative stress and antioxidant activity, improving synaptic plasticity and involving cognitive formation. Although previous studies showed that testosterone deficiency is positively correlated with cognitive impairment and insulin-resistant obesity, several studies demonstrated contradictory findings. Thus, this review comprehensively summarizes the current evidence from in vitro, in vivo and clinical studies of the relationship between testosterone deficiency and insulin-resistant obesity as well as the correlation between either insulin-resistant obesity or testosterone deficiency and cognitive impairment. Controversial reports and the mechanistic insights regarding the roles of testosterone in insulin-resistant obesity and cognitive function are also presented and discussed.

Relationships between testosterone levels and cognition in patients with Alzheimer disease and nondemented elderly men

BACKGROUND/AIMS

Previous research suggests that low levels of testosterone may be associated with the development of Alzheimer disease (AD), as well as poorer performance on certain neuropsychological tests and increased risk of depression.

METHODS

This study utilized data from 61 nondemented older men and 68 men with probable AD.

RESULTS

Testosterone levels did not differ between the groups. Regression analyses in men with AD revealed that testosterone levels did not significantly predict performance on neuropsychological tests or a measure of depression. Among controls, testosterone levels predicted estimated premorbid verbal IQ and performance on a verbal fluency test.

CONCLUSION

Findings suggest that testosterone is not associated with most neuropsychological test performances in patients with AD.

Effects of gonadal hormones on cognitive behaviour in elderly men and women

Over the last four decades, animal and cell culture studies have shown that sex steroids can have protective effects on the ageing brain. Limited short-term positive effects (2-4 months) of oestrogen treatment were found in women without (as well as with) dementia. By contrast to these initial promising findings, several large treatment studies showed that longer-term oestrogen treatment, particularly when given in combination with progesterone, could exert negative effects on cognitive function in women aged over 65 years. Several observational studies of older women and men also suggest that longer exposure to higher endogenous oestrogen levels at an older age might confer risk for accelerated cognitive decline and dementia. However, health of participants may modify this association and, in women closer to the age at the onset of menopause, positive associations of oestrogens with cognition were also found. The 'healthy cell bias' theory suggests that oestrogens have protective effects in healthy neurones, although cells undergoing pathological change show acceleration in their demise when exposed to oestrogens. In older men, most studies reported higher bioavailable testosterone levels to be associated with better cognitive function. Other studies have reported optimal testosterone levels for better global cognitive function and a reduced risk of cognitive decline. Variation in health status over time and the use of (in)sensitive cognitive tests and hormone assays may explain why this was not always found. In older women, this association (of testosterone with cognition) is less clear. Small studies reported some benefits of testosterone treatment in combination with oestrogen on cognition, although these were of short duration. Several observational studies, on the other hand, found negative associations between high testosterone levels and worse cognitive function in older women. Age, health status, duration of treatment and sex may thus modify effects of longer-term elevated sex steroid levels on brain function.

Hair testosterone and visuospatial memory in middle-aged men and women with and without depressive symptoms

BACKGROUND

Testosterone binds to androgen receptors, which can be found abundantly in the hippocampus. Associations between testosterone levels and visuospatial memory have been reported, albeit with inconsistent results. Previous studies have used point sampling of testosterone levels (blood, saliva) rather than long-term secretion measures. Hair analysis for steroids allows for retrospective ascertainment of cumulative steroid measures over several months. We examined hair testosterone and its association with verbal and visuospatial memory in middle-aged men and women with and without major depression.

METHODS

We examined a total of 73 middle-aged individuals (35 depressed patients, and 38 age-, sex- and education-matched healthy subjects). We tested verbal (Auditory Verbal Learning Task) and visuospatial (Rey figure) memory and measured testosterone in the hair by liquid chromatography tandem mass spectrometry.

RESULTS

Hair testosterone levels did not differ between patients and controls (mean 1.35pg/mg vs. 1.40pg/mg, SD 0.61 and 0.80, respectively). In men (n=24) but not women (n=49), hair testosterone was associated with visuospatial memory in a multiple regression analysis after controlling for age, education, body mass index, and depression (adjusted R(2)=0.56).

CONCLUSIONS

With the new method of testosterone measurement in hair allowing for long-term cumulative ascertainment of testosterone secretion, we extend recent results of a male-specific role for testosterone in visuospatial memory.

Endogenous Sex Hormones and Cognitive Function in Older Adults

Estrogen and testosterone may influence cognition in older adults, but the relationship between sex hormones and cognitive function is complex. The aim of this systematic review is to examine the role of sex hormones in cognitive function among older adults. A comprehensive, electronic review of literature was performed. Inclusion criteria were original quantitative research, written in English, used human subjects with a mean age of ≥60 years, and published from January 1997 through May 2012. Findings were mixed, although potential patterns were identified. Estradiol levels were potentially associated with benefits to episodic memory, semantic memory, verbal memory, and verbal learning in females only. The association between testosterone and cognitive function was mixed in both genders. Mixed findings may have been influenced by methodological differences and future studies should include research designs with ample rigor, sufficiently powered samples, consistent cognitive measurements, and clear descriptions of handling and storage of biological specimens.

Effect of estrogen and testosterone replacement therapy on cognitive fatigue

Both estrogen and testosterone insufficiency has been associated with reduced psychological well-being including fatigue. However, hormonal replacement studies on fatigue are rare. Therefore, we wanted to study the effect of testosterone and estrogen replacement therapy on cognitive fatigue and the relation between sex hormone levels and cognitive fatigue in oophorectomized women. Fifty women with surgically induced menopause (mean age: 54.0 ± 2.9 years) were randomly assigned to treatment with estradiol valerate in combination with testosterone undecanoate or placebo for 24 weeks in a double-blind cross-over study. Neuropsychological tests and questionnaires were used to assess cognitive fatigue and psychological well-being. Cognitive fatigue was significantly associated to poor self-rated health and higher body mass index but not to general psychological well-being or sex hormone levels. Treatment with testosterone + estrogen had no significant effect on cognitive fatigue but the results indicated a curvilinear relation for hormonal levels. The estrogen/testosterone ratio was more related to functions rather than high or low hormone levels per se. We found that cognitive fatigue is frequent in oophorectomized women and negatively associated to self-perceived health and positively associated to BMI. A well-balanced ratio between estrogen and testosterone levels may be important for cognitive fatigue.

Gender differences in verbal learning in older participants

Gender differences in cognitive function may diminish with age. We investigated gender and gender-by-age interactions in relation to verbal learning. Cross-sectional data were available from seven cohorts. Meta-analyses indicated that overall verbal learning favored women. Performance declined with age for both genders and there was little difference between genders in the rate of decline in healthy elderly cohorts. However, impoverished older cohorts with poor health and slightly better educated men showed trends for a male advantage occurring from the age of 70 years onwards. The reverse was seen in cohorts where more women had better education and showed less decline with an older age. Controlling for education in analyses did not affect this systematic bias. Slight demographic differences within cohorts may affect gender sensitive tests with age. However, gender differences are small in the elderly and do not indicate a need for separate gender norms for immediate verbal recall dementia screening tests.

Testosterone levels in healthy men are related to amygdala reactivity and memory performance

Testosterone is a steroid hormone thought to influence both emotional and cognitive functions. It is unknown, however, if testosterone also affects the interaction between these two domains, such as the emotional arousal-induced enhancement of memory. Healthy subjects (N=234) encoded pictures taken from the International Affective Picture System (IAPS) during functional magnetic resonance imaging (fMRI) and underwent a free recall test 10 min after memory encoding. We show that higher endogenous testosterone levels at encoding were associated with higher arousal ratings of neutral pictures in men. fMRI analysis revealed that higher testosterone levels were related to increased brain activation in the amygdala during encoding of neutral pictures. Moreover, endogenous testosterone levels were positively correlated with the number of freely recalled neutral pictures. No such relations were found in women. These findings point to a male-specific role for testosterone in enhancing memory by increasing the biological salience of incoming information.

Sex hormones, aging, and Alzheimer's disease

A promising strategy to delay and perhaps prevent Alzheimer's disease (AD) is to identify the age-related changes that put the brain at risk for the disease. A significant normal age change known to result in tissue-specific dysfunction is the depletion of sex hormones. In women, menopause results in a relatively rapid loss of estradiol and progesterone. In men, aging is associated with a comparatively gradual yet significant decrease in testosterone. We review a broad literature that indicates age-related losses of estrogens in women and testosterone in men are risk factors for AD. Both estrogens and androgens exert a wide range of protective actions that improve multiple aspects of neural health, suggesting that hormone therapies have the potential to combat AD pathogenesis. However, translation of experimental findings into effective therapies has proven challenging. One emerging treatment option is the development of novel hormone mimetics termed selective estrogen and androgen receptor modulators. Continued research of sex hormones and their roles in the aging brain is expected to yield valuable approaches to reducing the risk of AD.

Testosterone levels and cognition in elderly men: a review

Average testosterone levels and many cognitive functions show a decline with age. There is evidence to suggest that this association is not just age related. Results from cell culture and animal studies provide convincing evidence that testosterone could have protective effects on brain function. Alzheimer's disease (AD) is characterised by brain pathology affecting cognitive function and AD prevalence increases with age. Testosterone levels are lower in AD cases compared to controls, and some studies have suggested that low free testosterone (FT) may precede AD onset. Men with AD may show accelerated endocrinological ageing, characterised by an earlier lowering of thyroid stimulating hormone, an earlier increase in sex hormone binding globulin (SHBG), a subsequent earlier decrease in FT and an earlier increase in gonadotropin levels in response to this. Positive associations have been found between testosterone levels and global cognition, memory, executive functions and spatial performance in observational studies. However, non-significant associations were also reported. It may be that an optimal level of testosterone exists at which some cognitive functions are improved. This may be modified with an older age, with a shifting of the optimal testosterone curve to maintain cognition to the left and a lower optimal level thus needed to be beneficial for the brain. Genetic factors, such as APOE and CAG polymorphisms may further interact with testosterone levels in their effects on cognition. The roles of SHBG, gonadotropins, thyroid hormones and estrogens in maintaining cognitive function and preventing dementia in men are also not completely understood and should be investigated further. Hypogonadal men do not seem to benefit from testosterone supplementation but small scale, short term intervention studies in eugonadal men with and without cognitive impairments have shown promising results. Larger randomised, controlled trials are needed to further investigate testosterone treatment in protecting against cognitive decline and/or dementia.

Endogenous estradiol is associated with verbal memory in nondemented older men

This study examined the relationship between endogenous hormones and cognitive function in nondemented, ethnically-diverse community-dwelling older men enrolled in the Einstein Aging Study (EAS). All eligible participants (185 men, mean age=81 years) received neuropsychological assessment (Free and Cued Selective Reminding Test (FCSRT), Logical Memory (LM), Trail Making Test B (TMTB), block design (BD)) and provided blood samples for hormonal assays (total estradiol, total testosterone, calculated free testosterone index). Linear regression analysis adjusted for age, education, body mass index, and cardiovascular comorbidities indicated that men with high levels of total estradiol demonstrated better FCSRT verbal memory performance (β=0.17, p<0.02) compared to men with lower levels of total estradiol. The results remained unchanged when the model was further adjusted for ethnicity. We did not detect an association between testosterone and cognitive performance. These findings indicate that high levels of total estradiol in older men are associated with better performance on a cue-based, controlled learning test of verbal memory that is a sensitive predictor of dementia.