There is an urgent need to understand the nature of awareness in people with severe Alzheimer’s disease (AD) to ensure effective person-centered care. Objective biomarkers of awareness validated in other clinical groups (e.g., anesthesia, minimally conscious states) offer an opportunity to investigate awareness in people with severe AD. In this article we demonstrate the feasibility of using Transcranial magnetic stimulation (TMS) combined with EEG, event related potentials (ERPs) and fMRI to assess awareness in severe AD. TMS-EEG was performed in six healthy older controls and three people with severe AD. The perturbational complexity index (PCIST) was calculated as a measure of capacity for conscious awareness. People with severe AD demonstrated a PCIST around or below the threshold for consciousness, suggesting reduced capacity for consciousness. ERPs were recorded during a visual perception paradigm. In response to viewing faces, two patients with severe AD provisionally demonstrated similar visual awareness negativity to healthy controls. Using a validated fMRI movie-viewing task, independent component analysis in two healthy controls and one patient with severe AD revealed activation in auditory, visual and fronto-parietal networks. Activation patterns in fronto-parietal networks did not significantly correlate between the patient and controls, suggesting potential differences in conscious awareness and engagement with the movie. Although methodological issues remain, these results demonstrate the feasibility of using objective measures of awareness in severe AD. We raise a number of challenges and research questions that should be addressed using these biomarkers of awareness in future studies to improve understanding and care for people with severe AD.
Deficits in social cognition and function are characteristic of dementia, commonly accompanied by a loss of awareness of the presence or extent of these deficits. This lack of awareness can impair social relationships, increase patients’ and carers’ burden, and contribute to increased rates of institutionalization. Despite clinical importance, neural correlates of this complex phenomenon remain unclear. We conducted a systematic search of five electronic databases to identify functional and structural neuroimaging studies investigating the neural correlates of impaired awareness of social cognition and function in any dementia type. We rated study quality and conducted a narrative synthesis of the results of the eight studies that met the predefined eligibility criteria. Across these studies, deficits in awareness of impairments in social cognition and function were associated with structural or functional abnormalities in the frontal pole, orbitofrontal cortex, temporal pole, middle temporal gyrus, inferior temporal gyrus, fusiform gyrus, amygdala, hippocampus, parahippocampal gyrus, and insula. Several identified regions overlap with established neural correlates of social cognition. More research is needed to understand awareness of social cognition and function and how this becomes impaired in dementia to improve neuroscientific understanding, aid the identification of this problematic symptom, and target interventions to reduce burden and improve care.
Background Predictions about future dementia prevalence vary but usually suggest large increases in numbers of people with dementia as the population ages. However, in some countries, for example, the US, UK and Netherlands, while overall numbers of people with dementia are growing as predicted, the age‐specific incidence rates of dementia have decreased substantially. This is probably due to educational, socio‐economic, health and lifestyle changes. Method We reviewed known risk factors listed in the 2017 Lancet commission: education, hypertension, hearing impairment, smoking, obesity, depression, exercise, diabetes and social contact; literature about cognitive reserve and considered effective interventions for these risks. Result Cognitive reserve is the brain resilience which allows for cognition maintenance despite neuropathological damage. Early, mid and late life factors are all important. Early‐life factors, such as education, are important for cognitive reserve and those with more education build greater cognitive reserve. Lifelong higher educational attainment also reduces dementia risk. Cognitive reserve is not static and is affected by a number of factors. Quantifying it uses proxy measures such as education, residual approaches (the variance of cognition not explained by demographic variables and brain measures) or identifying underlying brain functional. People in more cognitively demanding jobs tend to show less cognitive deterioration before, and sometimes after retirement than those in less demanding jobs. Hypertension and obesity in mid‐life are risk factors for dementia, as is hearing impairment. More frequent social contacts at age 60 years is associated with lower dementia risk over 15 years of follow‐up. Smoking in late life increases the risk of dementia. In later life people’s physical health may moderate the susceptibility to neuropathology. Those who are frail may develop Alzheimer’s disease with a lesser burden of neuropathology. Older people otherwise in good physical health can sustain a higher burden of neuropathology without cognitive impairment. There are however relatively few evidence based interventions and we will discuss what interventions we found in systematic review and what developments are still needed. Conclusion There are clinically and economically effective interventions. It is important to consider the stage of the life course when thinking about possible effective interventions to prevent dementia.
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