Cognitive correlates of reduced driving performance in healthy older adults: A meta-analytic review

AIMS / OBJECTIVES

This meta-analytic review examines the evidence for the relationship between cognitive function and driving performance in older adults. The primary aims of this review were: (a) to identify cognitive correlates of reduced driving performance in older adults and (b) to determine whether such measures reliably predict reductions in driving performance over time.

METHODS

This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Peer reviewed studies that examined the (cross-sectional or longitudinal) relationship between standardised neuropsychological test performance measures and driving performance (e.g., via an on-road test, in-vehicle monitoring system, hazard perception test or driving simulator) in healthy adults aged 60 years and older, were included.

RESULTS/DISCUSSION

Eighteen studies were eligible for inclusion, of which 12 met requirements for meta-analysis. The results indicated that reaction time and Trail Making Test (TMT) A scores exhibited small-to-moderate correlations with driving performance, with moderate effects identified for block design, TMT B, Useful Field of View (UFOV) 2 and 3 tests. Further, no significant relationships were observed between the Mini-Mental State Examination and UFOV 1 with driving performance. Due to a paucity of data, the longitudinal relationship between such measures and driving could not be identified. The findings highlight (a) the potential of cognitive assessments to identify older adults at risk of driving impairment (as part of a larger diagnostic assessment), and (b) the urgent need for prospective longitudinal studies in investigating the impact of age-related changes in cognition on driving performance over time.

Sex-Specific Protective Effects of Cognitive Reserve on Age-Related Cognitive Decline: A 5-Year Prospective Cohort Study

BACKGROUND AND OBJECTIVES

Females have a higher age-adjusted incidence of Alzheimer disease than males but the reasons for this remain unclear. One proposed contributing factor is that, historically, females had less access to education and, therefore, may accumulate less cognitive reserve. However, educational attainment is confounded by IQ, which in itself is a component of cognitive reserve and does not differ between sexes. Steeper age-related cognitive declines are associated with increased risk of dementia. We, therefore, evaluated the moderating effects of 2 proxies for cognitive reserve, education and IQ, on the steepness of age-related declining cognitive trajectories in unimpaired older males and females.

METHODS

The Tasmanian Healthy Brain Project, a long-term cohort study, recruited healthy Australians aged 50-80 years without cognitive impairment. Baseline cognitive reserve was measured using educational history and IQ, measured by the Wechsler Test of Adult Reading, Full Scale Predicted IQ (WTAR-FSIQ). Cognitive trajectories for language, executive function, and episodic and working memory over 5 years were extracted from neuropsychological assessments. The adjusted effects of education, estimated IQ, and APOE allelic variant on cognitive trajectories were compared between males and females.

RESULTS

Five hundred sixty-two individuals (mean [SD] age 60 [6.7] years; 68% male; 33% APOE ε4+) were followed up over 5 years with 1,924 assessments and 24,946 cognitive test scores (annualized attrition rate 6.6% per year). Estimated IQ correlated with years of education (p < 0.001). Estimated IQ interacted with sex to moderate age-related cognitive trajectories (p = 0.03; adjusted for education); lower IQ males experienced steeper declining trajectories than higher IQ males, but lower IQ females had similar steepness of declining trajectories to higher IQ females. Education was not associated with rate of cognitive decline (p = 0.67; adjusted for WTAR-FSIQ). There were no significant differences in age-related cognitive trajectories between APOE genotypes in either sex.

DISCUSSION

IQ, a measure of cognitive reserve, predicted the steepness of declining cognitive trajectories in males only. Education did not explain as much variation in cognitive trajectories as IQ. Our findings do not support the hypothesis that historical sex disparities in access to education contribute to the higher female incidence of Alzheimer disease.

Path analysis of biomarkers for cognitive decline in early Parkinson’s disease

Clinical and biochemical diversity of Parkinson’s disease (PD) and numerous demographic, clinical, and pathological measures influencing cognitive function and its decline in PD create problems with the determination of effects of individual measures on cognition in PD. This is particularly the case where these measures significantly interrelate with each other producing intricate networks of direct and indirect effects on cognition. Here, we use generalized structural equation modelling (GSEM) to identify and characterize significant paths for direct and indirect effects of 14 baseline measures on global cognition in PD at baseline and at 4 years later. We consider 269 drug-naïve participants from the Parkinson’s Progression Marker Initiative database, diagnosed with idiopathic PD and observed for at least 4 years after baseline. Two GSEM networks are derived, highlighting the possibility of at least two different molecular pathways or two different PD sub-types, with either CSF p-tau181 or amyloid beta (1–42) being the primary protein variables potentially driving progression of cognitive decline. The models provide insights into the interrelations between the 14 baseline variables, and determined their total effects on cognition in early PD. High CSF amyloid concentrations (> 500 pg/ml) are associated with nearly full protection against cognitive decline in early PD in the whole range of baseline age between 40 and 80 years, and irrespectively of whether p-tau181 or amyloid beta (1–42) are considered as the primary protein variables. The total effect of depression on cognition is shown to be strongly amplified by PD, but not at the time of diagnosis or at prodromal stages. CSF p-tau181 protein could not be a reliable indicator of cognitive decline because of its significantly heterogeneous effects on cognition. The outcomes will enable better understanding of the roles of the clinical and pathological measures and their mutual effects on cognition in early PD.

Fronto-temporal functional disconnection precedes hippocampal atrophy in clinically confirmed multi-domain amnestic Mild Cognitive Impairment

Mild Cognitive Impairment (MCI) is fraught with high false positive diagnostic errors. The high rate of false positive diagnosis hampers attempts to identify reliable and valid biomarkers for MCI. Recent research suggests that aberrant functional neurocircuitries emerge prior to significant cognitive deficits. The aim of the present study was to examine this in clinically confirmed multi-domain amnestic-MCI (mdaMCI) using an established, multi-time point, methodology for minimizing false positive diagnosis. Structural and resting-state functional MRI data were acquired in healthy controls (HC, n=24), clinically-confirmed multi-domain amnestic-MCI (mdaMCI, n=14) and mild Alzheimer's Dementia (mAD, n=6). Group differences in cortical thickness, hippocampal volume and functional connectivity were investigated. Hippocampal subvolumes differentiated mAD from HC and mdaMCI. Functional decoupling of fronto-temporal networks implicated in memory and executive function differentiated HC and mdaMCI. Decreased functional connectivity in these networks was associated with poorer cognitive performance scores. Preliminary findings suggest the large-scale decoupling of fronto-temporal networks associated with cognitive decline precedes measurable structural neurodegeneration in clinically confirmed MCI and may represent a potential biomarker for disease progression.

Protein prescription and delivery practices in critically ill adults: A survey of Australian and New Zealand intensive care dietitians

BACKGROUND

Protein provision is thought to be integral to attenuating muscle wasting in critical illness, yet patients receive half of that prescribed. As international guidelines lack definitive evidence to support recommendations, understanding clinicians' views relating to protein practices is of importance.

OBJECTIVES

The objective of this study was to describe Australia and New Zealand intensive care unit (ICU) dietitians' protein prescription and perceived delivery practices in critically ill adults, including common barriers and associations between ICU clinical experience and protein prescriptions for different clinical conditions.

METHODS

A 42-item descriptive quantitative survey of Australian and New Zealand intensive care dietitians was disseminated through nutrition and ICU society e-mailing lists. Data were collected on respondent demographics and reported protein practices including questions related to a multitrauma case study. Data were analysed using descriptive and content analysis and reported as n (%). Fisher's exact tests were used to compare experience and protein prescriptions.

RESULTS

Of the 67 responses received (one excluded due to >50% missing data), more than 80% of respondents stated they would prescribe 1.2-1.5 g protein/kg bodyweight/day for most critically ill patients, most commonly using European Society of Clinical Nutrition and Metabolism (ESPEN) guidelines to support prescriptions (n = 61/66, 92%). Most respondents (n = 49/66, 74%) thought their practice achieved 61-80% of protein prescriptions, with frequently reported barriers including fasting periods (n = 59/66, 89%), avoiding energy overfeeding (n = 50/66, 76%), and gastrointestinal intolerance (n = 47/66, 71%). No associations between years of ICU experience and protein prescriptions for 14 of the 15 predefined clinical conditions were present.

CONCLUSIONS

Australian and New Zealand ICU dietitians use international guidelines to inform protein prescriptions of 1.2-1.5 g/kg/day for most clinical conditions, and protein prescriptions do not appear to be influenced by years of ICU experience. Key perceived barriers to protein delivery including avoidance of energy overfeeding and gastrointestinal intolerance could be explored to improve protein adequacy.

Studying at university in later life slows cognitive decline: A long-term prospective study

INTRODUCTION

Declining cognition in later life is associated with loss of independence and quality of life. This decline in cognition may potentially be reduced or reversed through engaging in cognitively stimulating activities. This study examined the potential for university attendance in later life to enhance cognitive function in older adults.

METHODS

Cognitively unimpaired adults (n = 485, 69% female, median age 60 years) were given the opportunity to undertake free university study. Repeated neurocognitive assessment was performed over 7 years.

RESULTS

Participants in the university education group (n = 383) improved z = .02 SD (.01, .03) per year of the study compared to controls (P = .001; averaged across a battery of cognitive tests). The largest improvements were observed on tests of language and verbal learning, memory, and episodic memory.

DISCUSSION

Later-life university study was associated with improved cognitive trajectories. Later-life education may preserve cognitive function, specifically for functions associated with communication, social interaction, and maintaining independence.

Association Between Components of Cognitive Reserve and Serum BDNF in Healthy Older Adults

Background: The brain-derived neurotrophic factor (BDNF) protein has been shown to have a prominent role in neuron survival, growth, and function in experimental models, and the BDNF Val66Met polymorphism which regulates its expression has been linked to resilience toward the effects of aging on cognition. Cognitively stimulating activity is linked to both increased levels of BDNF in the brain, and protection against age-related cognitive decline. The aim of this study was to investigate the associations between serum BDNF levels, the BDNF Val66Met genotype, and components of cognitive reserve in early and mid-life, measured with the Lifetime of Experiences Questionnaire (LEQ). Methods: Serum BDNF levels were measured cross-sectionally in 156 participants from the Tasmanian Healthy Brain Project (THBP) cohort, a study examining the potential benefits of older adults engaging in a university-level education intervention. Multiple linear regression was used to estimate serum BDNF's association with age, education, gender, BDNF Val66Met genotype, later-life university-level study, and cognitively stimulating activities measured by the LEQ. Results: Serum BDNF in older adults was associated with early life education and training, increasing 0.007 log(pg/ml) [95%CI 0.001, 0.012] per unit on the LEQ subscale. Conversely, education and training in mid-life were associated with a -0.007 log(pg/ml) [-0.012, -0.001] decrease per unit on the LEQ subscale. Serum BDNF decreased with age (-0.008 log(pg/ml) [-0.015, -0.001] per year), and male gender (-0.109 log(pg/ml) [-0.203, -0.015]), but mean differences between the BDNF Val66Met polymorphisms were not significant (p = 0.066). All effect sizes were small, with mid-life education and training having the largest effect size ( η p 2 = 0.044). Conclusion: Education in both early and mid-life explained small but significant amounts of variance in serum BDNF levels, more than age or gender. These effects were opposed and independent, suggesting that education at different stages of life may be associated with different cognitive and neural demands. Education at different stages of life may be important covariates when estimating associations between other exposures and serum BDNF.

The My Active and Healthy Aging ICT platform prevents quality of life decline in older adults: a randomised controlled study

INTRODUCTION

Prevention of frailty is paramount in older adults. We evaluated the efficacy of a tailored multidomain intervention, monitored with the My Active and Healthy Aging platform, in reducing conversion from a prefrail status to overt frailty and preventing decline in quality of life.

METHODS

We performed a multicentre, multicultural, randomised control study. The effects of multidomain interventions on frailty parameters, quality of life, physical, cognitive, psychosocial function, nutrition and sleep were evaluated in a group of 101 prefrail older subjects and compared with 100 prefrail controls, receiving general health advice.

RESULTS

At the 12-month assessment, controls showed a decline in quality of life that was absent in the active group. In addition, active participants showed an increase in mood and nutrition function. No effect on remaining parameter was observed.

DISCUSSION

Our study supports the use of personalised multidomain intervention, monitored with an information and communication technology platform, in preventing quality of life decline in older adults.

Associations of Later-Life Education, the BDNF Val66Met Polymorphism and Cognitive Change in Older Adults

In 358 participants of the Tasmanian Healthy Brain Project, we quantified the cognitive consequences of engaging in varying loads of university-level education in later life, and investigated whether or not BDNF Val66Met affected outcomes. Assessment of neuropsychological, health, and psychosocial function was undertaken at baseline, 12-month, and 24-month follow-up. Education load was positively associated with change in language processing performance, but this effect did not reach statistical significance (P = 0.064). The BDNF Val66Met polymorphism significantly moderated the extent to which education load was associated with improved language processing (P = 0.026), with education load having a significant positive relationship with cognitive change in BDNF Met carriers but not in BDNF Val homozygotes. In older adults who carry BDNF Met, engaging in university-level education improves language processing performance in a load-dependent manner.

Assessing mindfulness: Experimental support for the discriminant validity of breath counting as a measure of mindfulness but not self-report questionnaires

The current study sought to examine the discriminant validity of 3 commonly used measures of mindfulness. The discriminative ability of the Mindful Attention Awareness Scale (MAAS), the Five Factor Mindfulness Questionnaire (FFMQ), and a breath counting task (BCT) was assessed in a randomized control trial involving an 8-week mindfulness training (MT) condition (n = 53) and an active control computerized attention training (CT) program (n = 33). No evidence to support the discriminant validity of MAAS or FFMQ scores was found, as these self-report measures responded to both the MT and CT conditions. Breath counting scores however demonstrated unique responsiveness to the MT program, suggesting this behavioral task may be useful in measuring changes in mindfulness as it closely resembles core cognitive processes trained during this practice. Implications of these findings for the construct validity of both self-report and behavioral measures of mindfulness are discussed, along with the suitability of current mindfulness-based interventions in studies aiming to assess mindfulness outcomes. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Neural changes in early visual processing after 6 months of mindfulness training in older adults

Mindfulness has been shown to improve attentional performance, which is known to decline in aging. Long-latency electroencephalographic (EEG) event-related potential (ERP) changes have been reported immediately after mindfulness training, however the enduring stability of these effects is unknown. Furthermore, the ability of mindfulness to impact earlier stages of information processing is unclear. We examined neural activation using high density EEG in older adults engaged in mindfulness training to examine the long-term stability of training effects. After 6 months of training, mindfulness practitioners displayed enhanced neural activation during sensory encoding and perceptual processing of a visual cue. Enhanced perceptual processing of a visual cue was associated with increased neural activation during post-perceptual processing of a subsequent target. Similar changes were not observed in a control group engaged in computer-based attention training over the same period. Neural changes following mindfulness training were accompanied by behavioural improvements in attentional performance. Our results are suggestive of increased efficiency of the neural pathways subserving bottom-up visual processing together with an enhanced ability to mobilise top-down attentional processes during perceptual and post-perceptual processing following mindfulness training. These results indicate that mindfulness may enhance neural processes known to deteriorate in normal aging and age-related neurodegenerative diseases.

Reduced cerebral pressure-flow responses are associated with electrophysiological markers of attention in healthy older adults

The aim of this study was to determine the effect of age on the relationship between cerebrovascular function and the neural bases of sustained attention. Twenty-seven healthy young adults (aged 18-30 years) and 24 older adults (60-75 years) underwent assessments of cerebrovascular function and sustained attention. Blood flow velocity of the middle cerebral artery was assessed via Transcranial Doppler Ultrasound, during seated rest, in response to hypocapnic breathing (cerebrovascular reactivity) and during a repeated sit-to-stand procedure (pressure-flow response). Attentional processing was assessed using the N2 and P3 components of the event-related potential during a two-tone auditory oddball task. Poorer pressure-flow responses were significantly associated with reductions in N2 and P3 amplitude in the old group (b = -0.50, p = .029 and b = -0.46, p = .045), but not the young group. These results suggest that alterations in the brain's capacity to combat reductions in perfusion pressure are associated with age-related differences in attentional processing, supporting the hypothesis that cerebrovascular hemodynamic disturbances play a role in age-related cognitive decline.

Healthy aging affects cerebrovascular reactivity and pressure-flow responses, but not neurovascular coupling: A cross-sectional study

Background and purpose

Aging leads to alterations in cerebrovascular function, and these are thought to contribute to cognitive decline/dementia. Disturbances to cerebral blood flow regulation have been reported, but the findings are inconsistent and to date no study has comprehensively tested the collective and independent contribution of these parameters in the same age range. Such lines of enquiry are vital since aging is a heterogeneous and complex process, with cerebrovascular parameters being differentially affected depending on the individual. A multicomponent comprehensive measure of cerebrovascular function, which accounts for such diversity, is needed to differentiate between healthy young and old adults.

Methods

We tested the effect of aging on cerebrovascular function by comparing healthy young adults aged 18–30 and older adults aged 60–75, without cognitive impairments. Cerebrovascular blood flow velocity was assessed using transcranial Doppler ultrasound. Parameters included resting middle cerebral artery velocity (MCAv), neurovascular coupling, cerebrovascular reactivity to CO₂ (hypercapnia and hypocapnia), and the pressure-flow response during a sit-to-stand procedure.

Results

MANOVA revealed that collectively, the parameters discriminated the groups (p < .001). MCAv and pressure-flow responses were lower in the older group (p < .001). While there were no differences in hypercapnic responses (p = .908) and neurovascular coupling (p = .517), hypocapnic responses were elevated in the old (p = .002).

Conclusions

Collectively, cerebrovascular parameters can distinguish between healthy young and older adults, with aging leading to reductions in MCAv, and altering cerebrovascular reactivity and pressure-flow responses under hypotensive conditions.

The My Active and Healthy Aging (My-AHA) ICT platform to detect and prevent frailty in older adults: Randomized control trial design and protocol

INTRODUCTION

Frailty increases the risk of poor health outcomes, disability, hospitalization, and death in older adults and affects 7%-12% of the aging population. Secondary impacts of frailty on psychological health and socialization are significant negative contributors to poor outcomes for frail older adults.

METHOD

The My Active and Healthy Aging (My-AHA) consortium has developed an information and communications technology-based platform to support active and healthy aging through early detection of prefrailty and provision of individually tailored interventions, targeting multidomain risks for frailty across physical activity, cognitive activity, diet and nutrition, sleep, and psychosocial activities. Six hundred adults aged 60 years and older will be recruited to participate in a multinational, multisite 18-month randomized controlled trial to test the efficacy of the My-AHA platform to detect prefrailty and the efficacy of individually tailored interventions to prevent development of clinical frailty in this cohort. A total of 10 centers from Italy, Germany, Austria, Spain, United Kingdom, Belgium, Sweden, Japan, South Korea, and Australia will participate in the randomized controlled trial.

RESULTS

Pilot testing (Alpha Wave) of the My-AHA platform and all ancillary systems has been completed with a small group of older adults in Europe with the full randomized controlled trial scheduled to commence in 2018.

DISCUSSION

The My-AHA study will expand the understanding of antecedent risk factors for clinical frailty so as to deliver targeted interventions to adults with prefrailty. Through the use of an information and communications technology platform that can connect with multiple devices within the older adult's own home, the My-AHA platform is designed to measure an individual's risk factors for frailty across multiple domains and then deliver personalized domain-specific interventions to the individual. The My-AHA platform is technology-agnostic, enabling the integration of new devices and sensor platforms as they emerge.

Diagnostic Accuracy of Memory Measures in Alzheimer's Dementia and Mild Cognitive Impairment: a Systematic Review and Meta-Analysis

With an increasing focus on biomarkers in dementia research, illustrating the role of neuropsychological assessment in detecting mild cognitive impairment (MCI) and Alzheimer's dementia (AD) is important. This systematic review and meta-analysis, conducted in accordance with PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) standards, summarizes the sensitivity and specificity of memory measures in individuals with MCI and AD. Both meta-analytic and qualitative examination of AD versus healthy control (HC) studies (n = 47) revealed generally high sensitivity and specificity (≥ 80% for AD comparisons) for measures of immediate (sensitivity = 87%, specificity = 88%) and delayed memory (sensitivity = 89%, specificity = 89%), especially those involving word-list recall. Examination of MCI versus HC studies (n = 38) revealed generally lower diagnostic accuracy for both immediate (sensitivity = 72%, specificity = 81%) and delayed memory (sensitivity = 75%, specificity = 81%). Measures that differentiated AD from other conditions (n = 10 studies) yielded mixed results, with generally high sensitivity in the context of low or variable specificity. Results confirm that memory measures have high diagnostic accuracy for identification of AD, are promising but require further refinement for identification of MCI, and provide support for ongoing investigation of neuropsychological assessment as a cognitive biomarker of preclinical AD. Emphasizing diagnostic test accuracy statistics over null hypothesis testing in future studies will promote the ongoing use of neuropsychological tests as Alzheimer's disease research and clinical criteria increasingly rely upon cerebrospinal fluid (CSF) and neuroimaging biomarkers.

Further education improves cognitive reserve and triggers improvement in selective cognitive functions in older adults: The Tasmanian Healthy Brain Project

Introduction

The strong link between early-life education and subsequent reduced risk of dementia suggests that education in later life could enhance cognitive function and may reduce age-related cognitive decline and protect against dementia.

Methods

Episodic memory, working memory, executive function, and language processing performances were assessed annually over 4 years in 359 healthy older adults who attended university for a minimum of 12 months (intervention) and were compared against 100 healthy adult controls.

Results

Multiple group latent growth curve modeling revealed a significant improvement in language processing capacity over time in the intervention group. No changes were detected for episodic memory, working memory, or executive function.

Discussion

These results suggest that complex mental stimulation resulting from late-life further education results in improved crystallized knowledge but no changes to fluid cognitive functions.

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Early-life educational attainment predicts dementia.

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Early-life educational attainment predicts rate of cognitive decline.

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Late-life education in healthy adults improves language processing capacity.

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Late-life education enhances crystallized knowledge not fluid cognitive abilities.

Environmental novelty exacerbates stress hormones and Aβ pathology in an Alzheimer's model

Cognitive stimulation has been proposed as a non-pharmacological intervention to be used in primary, secondary and tertiary prevention approaches for Alzheimer's disease. A common familial Alzheimer's disease transgenic model showed heightened levels of the stress hormone, corticosterone. When exposed to periodic enhanced cognitive stimulation, these animals demonstrated further heightened levels of corticosterone as well as increased Aβ pathology. Hence, Alzheimer's disease may be associated with hypothalamic-pituitary-adrenal (HPA) axis dysfunction, causing stimulatory environments to become stress-inducing, leading to a glucocorticoid-pathology cycle contributing to further Aβ release and plaque formation. This finding suggests that stimulation-based interventions and local environments for people with Alzheimer's disease need to be designed to minimise a stress response that may exacerbate brain pathology.

Distinguishing the cognitive processes of mindfulness: Developing a standardised mindfulness technique for use in longitudinal randomised control trials

A capacity model of mindfulness is adopted to differentiate the cognitive faculty of mindfulness from the metacognitive processes required to cultivate this faculty in mindfulness training. The model provides an explanatory framework incorporating both the developmental progression from focussed attention to open monitoring styles of mindfulness practice, along with the development of equanimity and insight. A standardised technique for activating these processes without the addition of secondary components is then introduced. Mindfulness-based interventions currently available for use in randomised control trials introduce components ancillary to the cognitive processes of mindfulness, limiting their ability to draw clear causative inferences. The standardised technique presented here does not introduce such ancillary factors, rendering it a valuable tool with which to investigate the processes activated in mindfulness practice.

Validation of a Dynamic Measure of Current Cognitive Reserve in a Longitudinally Assessed Sample of Healthy Older Adults: The Tasmanian Healthy Brain Project

Cognitive reserve (CR) is a theoretical construct describing the underlying cognitive capacity of an individual that confers differential levels of resistance to, and recovery from, brain injuries of various types. To date, estimates of an individual's level of CR have been based on single proxy measures that are retrospective and static in nature. To develop a measure of dynamic change in CR across a lifetime, we previously identified a latent factor, derived from an exploratory factor analysis of a large sample of healthy older adults, as current CR (cCR). In the present study, we examined the longitudinal results of a sample of 272 older adults enrolled in the Tasmanian Healthy Brain Project. Using results from 12-month and 24-month reassessments, we examined the longitudinal validity of the cCR factor using confirmatory factor analyses. The results of these analyses indicate that the cCR factor structure is longitudinally stable. These results, in conjunction with recent results from our group demonstrating dynamic increases in cCR over time in older adults undertaking further education, lend weight to this cCR measure being a valid estimate of dynamic change in CR over time.

Age is no barrier: predictors of academic success in older learners

Although predictors of academic success have been identified in young adults, such predictors are unlikely to translate directly to an older student population, where such information is scarce. The current study aimed to examine cognitive, psychosocial, lifetime, and genetic predictors of university-level academic performance in older adults (50-79 years old). Participants were mostly female (71%) and had a greater than high school education level (M = 14.06 years, SD = 2.76), on average. Two multiple linear regression analyses were conducted. The first examined all potential predictors of grade point average (GPA) in the subset of participants who had volunteered samples for genetic analysis (N = 181). Significant predictors of GPA were then re-examined in a second multiple linear regression using the full sample (N = 329). Our data show that the cognitive domains of episodic memory and language processing, in conjunction with midlife engagement in cognitively stimulating activities, have a role in predicting academic performance as measured by GPA in the first year of study. In contrast, it was determined that age, IQ, gender, working memory, psychosocial factors, and common brain gene polymorphisms linked to brain function, plasticity and degeneration (APOE, BDNF, COMT, KIBRA, SERT) did not influence academic performance. These findings demonstrate that ageing does not impede academic achievement, and that discrete cognitive skills as well as lifetime engagement in cognitively stimulating activities can promote academic success in older adults.

A randomised control trial of the cognitive effects of working in a seated as opposed to a standing position in office workers

Sedentary behaviour is increasing and has been identified as a potential significant health risk, particularly for desk-based employees. The development of sit-stand workstations in the workplace is one approach to reduce sedentary behaviour. However, there is uncertainty about the effects of sit-stand workstations on cognitive functioning. A sample of 36 university staff participated in a within-subjects randomised control trial examining the effect of sitting vs. standing for one hour per day for five consecutive days on attention, information processing speed, short-term memory, working memory and task efficiency. The results of the study showed no statistically significant difference in cognitive performance or work efficiency between the sitting and standing conditions, with all effect sizes being small to very small (all ds < .2). This result suggests that the use of sit-stand workstations is not associated with a reduction in cognitive performance. Practitioner Summary: Although it has been reported that the use of sit-stand desks may help offset adverse health effects of prolonged sitting, there is scant evidence about changes in productivity. This randomised control study showed that there was no difference between sitting and standing for one hour on cognitive function or task efficiency in university staff.

Is APOE ε4 associated with poorer cognitive outcome following traumatic brain injury? A meta-analysis

OBJECTIVE

Cognitive impairment is a common sequelae of traumatic brain injury (TBI); however, predicting who will experience poorer outcomes remains challenging. A potential risk factor that has gained attention is the APOE gene, with the ε4 allele hypothesized to have a detrimental effect on post-TBI cognitive outcome. The aim of this meta-analysis was to evaluate the effect of APOE ε4 both in terms of general cognitive function and within specific domains known to be prone to impairment following TBI (executive function, working memory, verbal memory and visual memory).

METHOD

A literature search was undertaken in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA), resulting in the inclusion of 10 studies (ε4-carriers n = 143, noncarriers n = 510). Neuropsychological tasks were identified, and Cohen's d was calculated and pooled. Meta-analyses were conducted on general cognitive functioning and for the specific cognitive domains of interest.

RESULTS

No significant differences were found between APOE ε4-carriers or noncarriers, either in general cognitive function or in the cognitive domains of executive function, working memory, verbal memory, or visual memory.

CONCLUSIONS

This meta-analysis indicates that APOE ε4 does not have a detrimental effect on cognitive performance following TBI. We propose that the relationship between APOE and cognitive function following TBI is complex, and a more-nuanced exploration of APOE genotypes is needed. (PsycINFO Database Record

Exploring the effect of the apolipoprotein E (APOE) gene on executive function, working memory, and processing speed during the early recovery period following traumatic brain injury

INTRODUCTION

There is evidence that the e4 allele of the apolipoprotein E (APOE) gene is detrimental to cognitive function, but results from traumatic brain injury (TBI) populations are mixed. A possible explanation is that APOEe2 carriers have routinely been incorporated into APOEe4 and non-e4 groups, despite APOEe2 being proposed to have an ameliorative effect. Our primary aim was to investigate the influence of APOEe4 on cognitive impairment during early recovery following TBI, excluding the potential confound of APOEe2 possession. A secondary objective was to explore whether APOEe4 displays more pronounced effects in moderate to severe TBI and to consider the potential postinjury protective influence of the APOEe2 allele.

METHOD

Participants who recently sustained a TBI (posttraumatic amnesia > 5 minutes) were assessed on measures of information processing speed, executive function, and working memory upon remission of posttraumatic amnesia. APOE genotype was determined by buccal saliva DNA extraction (APOEe4 n = 37, APOEe3 n = 92, APOEe2 n = 13).

RESULTS

Stepwise multiple regressions were performed to compare APOEe4 carriers to APOEe3 homozygotes, with injury severity, age, and estimated premorbid IQ included in the first step. This model was found to significantly predict performance on all tasks, accounting for 17.3-24.3% of the variance. When APOEe4 status was added for the second step, there were no significant changes on any tasks (additional variance <1%). The effect of APOEe4 in moderate to severe TBI and the effect of APOEe2 were explored by analysis of covariance (ANCOVA), with no significant effects revealed.

CONCLUSIONS

It is unlikely that APOE genotype influences cognitive function in the initial recovery period following TBI, regardless of injury severity. However, a more nuanced and long-term exploration of the effect of APOE genotype in the TBI population is warranted.

Effect of Standing or Walking at a Workstation on Cognitive Function: A Randomized Counterbalanced Trial

OBJECTIVE

In the present study, we examined the effect of working while seated, while standing, or while walking on measures of short-term memory, working memory, selective and sustained attention, and information-processing speed.

BACKGROUND

The advent of computer-based technology has revolutionized the adult workplace, such that average adult full-time employees spend the majority of their working day seated. Prolonged sitting is associated with increasing obesity and chronic health conditions in children and adults. One possible intervention to reduce the negative health impacts of the modern office environment involves modifying the workplace to increase incidental activity and exercise during the workday. Although modifications, such as sit-stand desks, have been shown to improve physiological function, there is mixed information regarding the impact of such office modification on individual cognitive performance and thereby the efficiency of the work environment.

METHOD

In a fully counterbalanced randomized control trial, we assessed the cognitive performance of 45 undergraduate students for up to a 1-hr period in each condition.

RESULTS

The results indicate that there is no significant change in the measures used to assess cognitive performance associated with working while seated, while standing, or while walking at low intensity.

CONCLUSION

These results indicate that cognitive performance is not degraded with short-term use of alternate workstations.

Sending your grandparents to university increases cognitive reserve: The Tasmanian Healthy Brain Project

OBJECTIVE

Increasing an individual's level of cognitive reserve (CR) has been suggested as a nonpharmacological approach to reducing the risk for Alzheimer's disease. We examined changes in CR in older adults participating over 4 years in the Tasmanian Healthy Brain Project.

METHOD

A sample of 459 healthy older adults between 50 and 79 years of age underwent a comprehensive annual assessment of current CR, neuropsychological function, and psychosocial factors over a 4-year period. The intervention group of 359 older adults (M = 59.61 years, SD = 6.67) having completed a minimum of 12 months part-time university study were compared against a control reference group of 100 adults (M = 62.49 years, SD = 6.24) who did not engage in further education.

RESULTS

Growth mixture modeling demonstrated that 44.3% of the control sample showed no change in CR, whereas 92.5% of the further education participants displayed a significant linear increase in CR over the 4 years of the study. These results indicate that older adults engaging in high-level mental stimulation display an increase in CR over a 4-year period.

CONCLUSION

Increasing mental activity in older adulthood may be a viable strategy to improve cognitive function and offset cognitive decline associated with normal aging. (PsycINFO Database Record

Does the Cambridge Automated Neuropsychological Test Battery (CANTAB) Distinguish Between Cognitive Domains in Healthy Older Adults?

The Cambridge Neuropsychological Test Automated Battery (CANTAB) is a semiautomated computer interface for assessing cognitive function. We examined whether CANTAB tests measured specific cognitive functions, using established neuropsychological tests as a reference point. A sample of 500 healthy older (M = 60.28 years, SD = 6.75) participants in the Tasmanian Healthy Brain Project completed battery of CANTAB subtests and standard paper-based neuropsychological tests. Confirmatory factor analysis identified four factors: processing speed, verbal ability, episodic memory, and working memory. However, CANTAB tests did not consistently load onto the cognitive domain factors derived from traditional measures of the same function. These results indicate that five of the six CANTAB subtests examined did not load onto single cognitive functions. These CANTAB tests may lack the sensitivity to measure discrete cognitive functions in healthy populations or may measure other cognitive domains not included in the traditional neuropsychological battery.

KIBRA gene polymorphism has no association with verbal or visual episodic memory performance

Inter-individual variability in memory performance has been suggested to result, in part, from genetic differences in the coding of proteins involved in long-term potentiation (LTP). The present study examined the effect of a single-nucleotide polymorphism (SNP) in the KIBRA gene (rs17070145) on episodic memory performance, using multiple measures of verbal and visual episodic memory. A total of 256 female and 130 male healthy, older adults (mean age = 60.86 years) were recruited from the Tasmanian Healthy Brain Project (THBP), undergoing both neuropsychological and genetic testing. The current study showed no significant effect of the KIBRA polymorphism on performance on the Rey Auditory Verbal Learning Task, Logical Memory test, Paired Associates Learning test or Rey Complex Figure Task. The results suggest there is little to no functional significance of KIBRA genotype on episodic memory performance, regardless of modality.

Reducing false positive diagnoses in mild cognitive impairment: the importance of comprehensive neuropsychological assessment

BACKGROUND AND PURPOSE

Longitudinal studies of mild cognitive impairment (MCI) report that a sizeable proportion of MCI cases revert to normal levels of functioning over time. The rate of recovery from MCI indicates that existing MCI diagnostic criteria result in an unacceptably high rate of false positive diagnoses and lack adequate sensitivity and specificity.

METHODS

The aim of the present study was to identify a set of neuropsychological measures able to differentiate between true positive cases of MCI from those who were unimpaired at 11 months' follow-up.

RESULTS

A discriminant function analysis identified that a combination of measures of complex sustained attention, semantic memory, working memory, episodic memory and selective attention correctly classified outcome in more than 80% of cases. The rate of false positive diagnoses (5.93%) was considerably lower than is evident in previously published MCI studies.

CONCLUSIONS

The results of the present study indicate that the rate of false positive MCI diagnoses can be significantly reduced through the use of sensitive and specific neuropsychological measures of memory and non-memory functions.

APOE and BDNF Val66Met polymorphisms combine to influence episodic memory function in older adults

Genetic polymorphisms of apolipoprotein E (APOE) and brain-derived neurotrophic factor (BDNF) have shown inconsistent associations with healthy adult cognitive functions. Recent investigations have suggested that APOE polymorphisms do not contribute to non-pathological cognitive function and that any effect is likely due to prodromal Alzheimer's disease (AD). Similarly, although BDNF Val66Met polymorphisms affect hippocampal morphology and function, associations with learning and/or memory have not always been found. This study sought to determine whether APOE and BDNF polymorphisms were associated, either independently or in combination, with adult cognition. Comprehensive neuropsychological assessments were conducted on 433 older adults, aged 50-79 years (M=62.16, SD=6.81), which yielded measures of episodic memory, working memory, executive function, and language processing. Participants underwent comprehensive neuropsychological assessment to ensure that only cognitively intact individuals comprised the sample. APOE and BDNF polymorphic data were used as predictors in general linear models that assessed composite cognitive domain variables, while covarying for education and age. Although no main effects for APOE or BDNF were found, the analysis identified a significant APOE×BDNF interaction that predicted episodic memory performance (p=.02, η(2)=.02). Post-hoc analyses demonstrated that in BDNF Val homozygotes, the cognitive consequences of APOE polymorphisms were minimal. However, in BDNF Met carriers, the hypothesized beneficial/detrimental effects of APOE polymorphisms were found. Our data show that concurrent consideration of both APOE and BDNF polymorphisms are required in order to witness a cognitive effect in healthy older adults.

Lowered performance in working memory and attentional sub-processes are most prominent in multi-domain amnestic mild cognitive impairment subtypes

BACKGROUND

Research suggests that working memory and attention deficits may be present in mild cognitive impairment (MCI). However, the functional status of these domains within revised MCI subtypes remains unclear, particularly because previous studies have examined these cognitive domains with the same tests that were used to classify MCI subtypes. The aim of this study was to examine working memory and attention function in MCI subtypes on a battery of neuropsychological tests that were distinct from those used to classify MCI subtypes

METHODS

A total of 122 adults aged 60-90 years were classified at baseline as amnestic MCI, non-amnestic MCI, and multi-domain amnestic (a-MCI+). The attentional and working memory capacity of participants was examined using a battery of tests distinct from those used to classify MCI at screening.

RESULTS

The a-MCI+ group demonstrated the poorest performance on all working memory tasks and specific sub-processes of attention. The non-amnestic MCI group had lowered performance on visual span and complex sustained attention only. There was no evidence of either attentional or working memory impairment in the amnestic MCI participants.

CONCLUSION

When MCI cohorts are assessed on measures distinct from those used at classification, a-MCI+ subjects had the most compromised working memory and attention function. These results support previous findings that suggest a-MCI+ more closely resembles early stage Alzheimer's disease and those with a-MCI+ may be at increased rate of future cognitive decline compared to those with other MCI subtypes.

Endogenous amylin and glucagon-like peptide-1 concentrations are not associated with gastric emptying in critical illness

BACKGROUND

In health, the hormones amylin and glucagon-like peptide-1 (GLP-1) slow gastric emptying (GE) and modulate glycaemia. The aims of this study were to determine amylin and GLP-1 concentrations in the critically ill and their relationship with GE, glucose absorption and glycaemia.

METHODS

In fasted critically ill and healthy subjects (n = 26 and 23 respectively), liquid nutrient, containing 100 mg (13) C-sodium octanoate and 3 g 3-O-methlyglucose (3-OMG), was administered via a nasogastric tube. Amylin, GLP-1, glucose and 3-OMG concentrations were measured in blood samples taken during fasting, and 30 min and 60 min after the 'meal'. Breath samples were taken to determine gastric emptying coefficient (GEC). Intolerance to intragastric feeding was defined as a gastric residual volume of ≥ 250 ml and/or vomiting within the 24 h prior to the study.

RESULTS

Although GE was slower (GEC: critically ill 2.8 ± 0.9 vs. health, 3.4 ± 0.2; P = 0.002), fasting blood glucose was higher (7.0 ± 1.9 vs. 5.7 ± 0.2 mmol/l; P = 0.005) and overall glucose absorption was reduced in critically ill patients (3-OMG: 9.4 ± 8.0 vs. 17.7 ± 4.9 mmol/l.60 min; P < 0.001), there were no differences in fasting or postprandial amylin concentrations. Furthermore, although fasting [1.7 (0.4-7.2) vs. 0.7 (0.3-32.0) pmol/l; P = 0.04] and postprandial [3.0 (0.4-8.5) vs. 0.8 (0.4-34.3) pmol/l; P = 0.02] GLP-1 concentrations were increased in the critically ill and were greater in feed intolerant when compared with those tolerating feed [3.7 (0.4-7.2) vs. 1.2 (0.7-4.6) pmol/l; P = 0.02], there were no relationships between GE and fasting amylin or GLP-1 concentrations.

CONCLUSION

In the critically ill, fasting GLP-1, but not amylin, concentrations are elevated and associated with feed intolerance. Neither amylin nor GLP-1 appears to substantially influence the rate of GE.

Mesenteric blood flow, glucose absorption and blood pressure responses to small intestinal glucose in critically ill patients older than 65 years

PURPOSE

To compare nutrient-stimulated changes in superior mesenteric artery (SMA) blood flow, glucose absorption and glycaemia in individuals older than 65 years with, and without, critical illness.

METHODS

Following a 1-h 'observation' period (t (0)-t (60)), 0.9 % saline and glucose (1 kcal/ml) were infused directly into the small intestine at 2 ml/min between t (60)-t (120), and t (120)-t (180), respectively. SMA blood flow was measured using Doppler ultrasonography at t (60) (fasting), t (90) and t (150) and is presented as raw values and nutrient-stimulated increment from baseline (Δ). Glucose absorption was evaluated using serum 3-O-methylglucose (3-OMG) concentrations during, and for 1 h after, the glucose infusion (i.e. t (120)-t (180) and t (120)-t (240)). Mean arterial pressure was recorded between t (60)-t (240). Data are presented as median (25th, 75th percentile).

RESULTS

Eleven mechanically ventilated critically ill patients [age 75 (69, 79) years] and nine healthy volunteers [70 (68, 77) years] were studied. The magnitude of the nutrient-stimulated increase in SMA flow was markedly less in the critically ill when compared with healthy subjects [Δt (150): patients 115 (-138, 367) versus health 836 (618, 1,054) ml/min; P = 0.001]. In patients, glucose absorption was reduced during, and for 1 h after, the glucose infusion when compared with health [AUC(120-180): 4.571 (2.591, 6.551) versus 11.307 (8.447, 14.167) mmol/l min; P < 0.001 and AUC(120-240): 26.5 (17.7, 35.3) versus 40.6 (31.7, 49.4) mmol/l min; P = 0.031]. A close relationship between the nutrient-stimulated increment in SMA flow and glucose absorption was evident (3-OMG AUC(120-180) and ∆SMA flow at t (150): r (2) = 0.29; P < 0.05).

CONCLUSIONS

In critically ill patients aged >65 years, stimulation of SMA flow by small intestinal glucose infusion may be attenuated, which could account for the reduction in glucose absorption.

The effect of occupational exposure to manganese dust and fume on neuropsychological functioning in Australian smelter workers

Chronic low-level occupational exposure to manganese (Mn) is reportedly associated with the development of Parkinsonian-like symptoms. In a study of 143 manganese smelter workers, inhalable Mn exposure was associated with lower performances on the Digit Symbol Coding and Stroop tests; respirable Mn exposure was associated with improved Digit Symbol Coding test performance and reduced performance on the Trail Making (Part A), Matrix Reasoning, and Stroop tests. While these relationships reached statistical significance, the magnitude of these effects was significantly smaller than the standard error of measurement of the neuropsychological tests, indicating that these differences are not of clinical significance.

Increased inattentional blindness in severe traumatic brain injury: Evidence for reduced distractibility?

PRIMARY OBJECTIVE

To examine the role of selective attention and visual perception in medicating inattentional blindness in a severe traumatic brain injured sample.

RESEARCH DESIGN

Cross-sectional design with age and education matched control sample.

METHODS AND PROCEDURES

Twenty participants with severe traumatic brain injury (n = 10) and matched controls (n = 10) completed a series of tests of focused attention (Stroop test), divided attention (Trail Making Test), visual perception (Visual Object and Space Perception Battery) and two tasks of inattentional blindness.

MAIN OUTCOMES AND RESULTS

The group with severe TBI were significantly slower on the Stroop test and TMT and displayed significantly elevated Stroop interference and TMT ratio scores. On the inattentional blindness tasks, fewer TBI participants identified a distracting stimulus.

CONCLUSION

The results indicate severe TBI is associated with deficits to focused and divided attention with the finding of a potentially more debilitating impairment arising from reduced distractibility following severe TBI.