Undetected preclinical neurodegenerative disease in models of normal cognitive aging
AffiliationFlorey Department of Neuroscience and Mental Health
Document TypePhD thesis
Access StatusThis item is embargoed and will be available on 2021-01-11. This item is currently available to University of Melbourne staff and students only, login required.
© 2018 Dr. Karra Danyelle Harrington
With population aging, understanding cognitive changes that occur in late life is vital to support these increasing numbers of older adults to maintain their wellbeing and independence. Furthermore, accurate estimates of age-related cognitive change will enable the differentiation of early stage neurodegenerative disease from normal aging. Current cognitive aging models describe a pattern of progressive decline in memory,executive function, and processing speed abilities, and retention of experience-based knowledge, with increasing age. However, given that many older adults show signs of neurodegenerative disease, despite not meeting clinical criteria for dementia, it is possible that cognitive aging studies may have over-estimated the nature and magnitude of age-related cognitive decline. The aim of this thesis was to determine the extent to which undetected preclinical neurodegenerative disease could influence models of cognitive aging. Age-related change in cognition was examined in cognitively normal healthy older adults who underwent repeated clinical and neuropsychological assessments, as well as biomarker assessment for neurodegenerative disease. The influence of progression to mild cognitive impairment (MCI) and dementia was also considered. Results indicated that estimates of age-related cognitive decline were inflated by undetected disease. This was also found when the data were reconceptualised as intelligence factors and was confirmed across two cohorts and utilizing a range of analytic methods. Notably, in the absence of disease, increasing age was associated with stability of performance in episodic and working memory, and an attenuated rate of decline in some processing speed and executive functions. Together these results indicate that current expectations about cognitive loss in aging are biased by unrecognized neurodegenerative disease.
Keywordsageing; neurodegeneration; cognition; preclinical Alzheimer
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