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Capacity Assessment Across Functional Domains in Later Life  

Benjamin T. Mast and Diana DiGasbarro

Clinicians conduct capacity evaluations to determine an older adult’s ability to make and execute a decision within key domains of functioning. Questions of capacity often arise when an older adult experiences a decline in cognitive functioning due to Alzheimer’s disease, stroke, or severe psychiatric illness, for example. Capacity is related to legal competency, and a lack of capacity may be proved by providing evidence that an older adult is unable to understand the act or decision in question; appreciate the context and consequences of the decision or act; reason about the potential harms and benefits; or express a choice. Capacity is domain-specific, time-specific, and decision-specific. Domains include financial capacity, medical treatment and research consent capacity, driving capacity, sexual consent capacity, and voting capacity. Each capacity domain encompasses activities that may vary in complexity or risk, and thus require different levels of capacity. For example, within the medical treatment consent capacity domain, an older adult may lack the capacity to consent to a complicated and risky surgical procedure while retaining the capacity to consent to a routine blood draw. Clinicians determine capacity by using a combination of tools including capacity assessment instruments, task-specific functional evaluations, interviews with the patient and family members, measures of cognitive functioning, and consideration of social, physical, and mental health factors. Extensive research has been conducted to determine the reliability and validity of a variety of capacity assessment instruments for many domains. These instruments generally assess the patient’s responses to vignettes pertaining to the domain in question, information gleaned from structured and semi-structured interviews, functional ability, or a combination of these methods. Although there is still need for more research, especially in emerging domains, capacity assessments help to protect vulnerable older adults from harm while allowing them to retain the highest possible level of autonomy.


Intraindividual Reaction Time Variability, Attention, and Age-Related Outcomes  

David Bunce and Sarah Bauermeister

Intraindividual variability in the present context refers to the moment-to-moment variation in attentional or executive engagement over a given time period. Typically, it is measured using the response latencies collected across the trials of a behavioral neurocognitive task. In aging research, the measure has received a lot of recent interest as it may provide important insights into age-related cognitive decline and neuropathology as well as having potential as a neurocognitive assessment tool in healthcare settings. In the present chapter, we begin by reviewing the key empirical findings relating to age and intraindividual variability. Here, research shows that intraindividual variability increases with age and predicts a range of age-related outcomes including gait impairment, falls and errors more broadly, mild cognitive impairment, dementia, and mortality. Brain imaging research suggests that greater variability is associated with age-related or neuropathological changes to a frontal–cingulate–parietal network and that white matter compromise and dopamine depletion may be key underlying mechanisms. We then consider the cognitive and neurobiological theoretical underpinnings of the construct before providing a description of the various methods and metrics that have been used to compute measures of variability – reaction time cut-offs, raw and residualized intraindividual standard deviations, coefficient of variation, ex-Gaussian curve and fast Fourier transformation. A further section considers the range of neurocognitive tasks that have been used to assess intraindividual variability. Broadly, these tasks can be classified on a continuum of cognitive demands as psychomotor, executive control or higher-order cognitive tasks (e.g., episodic memory). Finally, we provide some pointers concerning the pressing issues that future research needs to address in the area. We conclude that the existing body of theoretical and empirical work underlines the potential of intraindividual reaction time variability measures as additions to the neuropsychological test batteries that are used in the early detection of a range of age-related neurocognitive disorders in healthcare settings.


Cognition and Mobility With Aging  

Karen Z. H. Li, Halina Bruce, and Rachel Downey

Research on the interplay of cognition and mobility in old age is inherently multidisciplinary, informed by findings from life span developmental psychology, kinesiology, cognitive neuroscience, and rehabilitation sciences. Early observational work revealed strong connections between sensory and sensorimotor performance with measures of intellectual functioning. Subsequent work has revealed more specific links between measures of cognitive control and gait quality. Convergent evidence for the interdependence of cognition and mobility is seen in patient studies, wherein cognitive impairment is associated with increased frequency and risk of falling. Even in cross-sectional studies involving healthy young and older adults, the effects of aging on postural control and gait are commonly exacerbated when participants perform a motor task with a concurrent cognitive load. This motor-cognitive dual-task method assumes that cognitive and motor domains compete for common capacity, and that older adults recruit more cognitive capacity than young adults to support gait and posture. Neuroimaging techniques such as magnetic resonance imaging (MRI) have revealed associations between measures of mobility (e.g., gait velocity and postural control) and measures of brain health (e.g., gray matter volumes, cortical thickness, white matter integrity, and functional connectivity). The brain regions most often associated with aging and mobility also appear to subserve high-level cognitive functions such as executive control, attention, and working memory (e.g., dorsolateral prefrontal cortex, anterior cingulate). Portable functional neuroimaging has allowed for the examination of neural functioning during real-time walking, often in conjunction with detailed spatiotemporal measures of gait. A more recent strategy that addresses the interdependence of cognitive and motor processes in old age is cognitive remediation. Cognitive training has yielded promising improvements in balance, walking, and overall mobility status in healthy older adults, and those with age-related neurodegenerative conditions such as Parkinson’s Disease.