Catherine MacLeod

Potentially modifiable lifestyle factors, cognitive reserve, and cognitive function in later life: A cross-sectional study

Background Potentially modifiable lifestyle factors may influence cognitive health in later life and offer potential to reduce the risk of cognitive decline and dementia. The concept of cognitive reserve has been proposed as a mechanism to explain individual differences in rates of cognitive decline, but its potential role as a mediating pathway has seldom been explored using data from large epidemiological studies. We explored the mediating effect of cognitive reserve on the cross-sectional association between lifestyle factors and cognitive function in later life using data from a population-based cohort of healthy older people. Methods and findings We analysed data from 2,315 cognitively healthy participants aged 65 y and over in the Cognitive Function and Ageing Study Wales (CFAS-Wales) cohort collected in 2011–2013. Linear regression modelling was used to investigate the overall associations between five lifestyle factors—cognitive and social activity, physical activity, diet, alcohol consumption, and smoking—and cognition, adjusting for demographic factors and chronic conditions. Mediation analysis tested for indirect effects of the lifestyle factors on cognition via cognitive reserve. After controlling for age, gender, and the presence of chronic conditions, cognitive and social activity, physical activity, healthy diet, and light-to-moderate alcohol consumption were positively associated with cognitive function, together accounting for 20% (95% CI 17%–23%) of variance in cognitive test scores. Cognitive reserve was an important mediator of this association, with indirect effects via cognitive reserve contributing 21% (95% CI 15%–27%) of the overall effect on cognition. The main limitations of the study derive from the cross-sectional nature of the data and the challenges of accurately measuring the latent construct of cognitive reserve. Conclusions Cross-sectional associations support the view that enhancing cognitive reserve may benefit cognition, and maintenance of cognitive health may be supported by a healthy and active lifestyle, in later life.

PRKCA Polymorphism Changes the Neural Basis of Episodic Remembering in Healthy Individuals

Everyday functioning relies on episodic memory, the conscious retrieval of past experiences, but this crucial cognitive ability declines severely with aging and disease. Vulnerability to memory decline varies across individuals however, producing differences in the time course and severity of memory problems that complicate attempts at diagnosis and treatment. Here we identify a key source of variability, by examining gene dependent changes in the neural basis of episodic remembering in healthy adults, targeting seven polymorphisms previously linked to memory. Scalp recorded Event-Related Potentials (ERPs) were measured while participants remembered words, using an item recognition task that requires discrimination between studied and unstudied stimuli. Significant differences were found as a consequence of a Single Nucleotide Polymorphism (SNP) in just one of the tested genes, PRKCA (rs8074995). Participants with the common G/G variant exhibited left parietal old/new effects, which are typically seen in word recognition studies, reflecting recollection-based remembering. During the same stage of memory retrieval participants carrying a rarer A variant exhibited an atypical pattern of brain activity, a topographically dissociable frontally-distributed old/new effect, even though behavioural performance did not differ between groups. Results replicated in a second independent sample of participants. These findings demonstrate that the PRKCA genotype is important in determining how episodic memories are retrieved, opening a new route towards understanding individual differences in memory.

Health and social exclusion in older age: Evidence from Understanding Society, the UK Household Longitudinal Study

Background Social exclusion of the elderly is a key policy focus but evidence on the processes linking health and social exclusion is hampered by the variety of ways that health is used in social exclusion research. We investigated longitudinal associations between health and social exclusion using an analytical framework that did not conflate them. Methods Data employed in this study came from 4 waves of Understanding Society, the UK Household Longitudinal Study 2009–2013. The sample comprised all adults who took part in all 4 waves, were 65 years or more in Wave 3, and had complete data on our variables of interest for each analysis. We used linear regression to model the relationship between Wave 2/3 social exclusion and Wave1–2 health transitions (N=4312) and logistic regression to model the relationship between Wave2/3 social exclusion and Wave 4 health states, conditional on Wave 3 health (N=4244). Results There was a dose–response relationship between poor health in Waves 1 and 2 and later social exclusion. Use of a car, mobile phone and the internet moderated the association between poor health and social exclusion. Given the health status in Wave 3, those who were more socially excluded had poorer outcomes on each of the three domains of health in Wave 4. Conclusions Use of the internet and technology protected older adults in poor health from social exclusion. Age-friendly hardware and software design might have public health benefits.

Re-thinking social exclusion in later life: A case for a new framework for measurement

ABSTRACT Social exclusion is a dynamic multi-dimensional process that is interactive in nature. The complex interplay between domains, whereby each domain can act as a determinant, indicator and/or outcome of social exclusion, hinders understanding of the process and the mechanisms through which social exclusion exists. This article highlights the need to disentangle these pathways and move beyond descriptive accounts of social exclusion, presenting a new working framework that allows direct hypothesis testing of these between-domain relationships. Whilst this working framework can be applied to any population, this article focuses on older adults. Life events that can drive social exclusion such as bereavement and changes in health are more likely to occur in later life, and occur more frequently, increasing the risk of social exclusion for this population. Rooted in the new working framework, this article presents the construction of later life social exclusion measures for use with Understanding Society – the United Kingdom Household Longitudinal Study. The validity of these measures are considered by examining the characteristics of those aged 65 years and over who score the highest, and therefore experience the greatest level of exclusion. This new working framework and developed social exclusion measures provide a platform from which to explore the complex relationships between domains of social exclusion and ultimately provide a clearer understanding of this intricate multi-dimensional process.

A functional electrical stimulation system for human walking inspired by reflexive control principles

This study presents an innovative multichannel functional electrical stimulation gait-assist system which employs a well-established purely reflexive control algorithm, previously tested in a series of bipedal walking robots. In these robots, ground contact information was used to activate motors in the legs, generating a gait cycle similar to that of humans. Rather than developing a sophisticated closed-loop functional electrical stimulation control strategy for stepping, we have instead utilised our simple reflexive model where muscle activation is induced through transfer functions which translate sensory signals, predominantly ground contact information, into motor actions. The functionality of the functional electrical stimulation system was tested by analysis of the gait function of seven healthy volunteers during functional electrical stimulation–assisted treadmill walking compared to unassisted walking. The results demonstrated that the system was successful in synchronising muscle activation throughout the gait cycle and was able to promote functional hip and ankle movements. Overall, the study demonstrates the potential of human-inspired robotic systems in the design of assistive devices for bipedal walking.

Correction: Reflex Control of Robotic Gait Using Human Walking Data

The following information is missing from the Funding section: Funding was provided by the University of Glasgow (http://www.gla.ac.uk) LKAS scholarship (http://www.gla.ac.uk/services/postgraduateresearch/scholarships/kelvinsmith/). This funding was received by LM. The complete, correct Funding statement is: Funding was provided by the Engineering and Physical Sciences Research Council (EPSRC) (http://www.epsrc.ac.uk/Pages/default.aspx) through the Doctoral Training Centre (DTC) in Medical Devices, University of Strathclyde (http://www.strath.ac.uk/simd/dtc/). This funding was received by CAM. Funding was also provided by the University of Glasgow (http://www.gla.ac.uk) LKAS scholarship (http://www.gla.ac.uk/services/postgraduateresearch/scholarships/kelvinsmith/). This funding was received by LM. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Seeking assistance in later life: how do older people evaluate their need for assistance?

Abstract Background legislation places an onus on local authorities to be aware of care needs in their locality and to prevent and reduce care and support needs. The existing literature overlooks ostensibly ‘healthy’ and/or non-users of specific services, non-health services and informal assistance and therefore inadequately explains what happens before or instead of individuals seeking services. We sought to address these gaps by exploring older adults’ accounts of seeking assistance in later life. Methods we conducted semi-structured qualitative interviews with 40 adults aged 68–95. We invited participants to discuss any type of support, intervention, or service provision, whether medical, social, family-provided, paid or unpaid. Findings this paper reports older people’s accounts of how they evaluated their need for assistance. We found that the people in our sample engaged in a recursive process, evaluating their needs on an issue-by-issue basis. Participants’ progression through this process hinged on four factors: their acknowledgement of decline; the perceived impact of decline on their usual activities and independence; their preparedness to be a recipient of assistance; and, the opportunity to assert their need. In lieu of seeking assistance, participants engaged in self-management, but also received unsolicited or emergency assistance. Conclusions older people’s adaptations to change and attempts to meet their needs without assistance mean that they do not present to services, limiting the local authority’s knowledge of their needs and ability to plan appropriate services. Our findings offer four stages for policymakers, service providers and carers to target to address the uptake of assistance.

Investigating the Functional Utility of the Left Parietal ERP Old/New Effect: Brain Activity Predicts Within but Not Between Participant Variance in Episodic Recollection

A success story within neuroimaging has been the discovery of distinct neural correlates of episodic retrieval, providing insight into the processes that support memory for past life events. Here we focus on one commonly reported neural correlate, the left parietal old/new effect, a positive going modulation seen in event-related potential (ERP) data that is widely considered to index episodic recollection. Substantial evidence links changes in the size of the left parietal effect to changes in remembering, but the precise functional utility of the effect remains unclear. Here, using forced choice recognition of verbal stimuli, we present a novel population level test of the hypothesis that the magnitude of the left parietal effect correlates with memory performance. We recorded ERPs during old/new recognition, source accuracy and Remember/Know/Guess tasks in two large samples of healthy young adults, and successfully replicated existing within participant modulations of the magnitude of the left parietal effect with recollection. Critically, however, both datasets also show that across participants the magnitude of the left parietal effect does not correlate with behavioral measures of memory – including both subjective and objective estimates of recollection. We conclude that in these tasks, and across this healthy young adult population, the generators of the left parietal ERP effect do not index performance as expected. Taken together, these novel findings provide important constraints on the functional interpretation of the left parietal effect, suggesting that between group differences in the magnitude of old/new effects cannot always safely be used to infer differences in recollection.