Characterising obstructive sleep apnoea in memory clinics: hypoxemia, memory, and structural brain changes

Abstract

Dementia is characterised by the progressive deterioration of cognitive function, leading to an impairment in activities of everyday life. Between 40-50% of dementia risk can be attributed to modifiable risk factors, warranting early intervention approaches for dementia prevention. Obstructive sleep apnoea (OSA) in midlife is associated with a 26% increased risk of dementia longitudinally. However, there is limited knowledge regarding these inter-relationships in older adults ‘at-risk’ for dementia. It is important to understand the links between OSA and neurodegeneration in these older samples, since this is a critical window for secondary prevention strategies. The current thesis aims to provide new knowledge regarding the inter-relationships between OSA and cognitive impairment in older adults seeking within a specialist memory clinic. The first study demonstrates that greater OSA severity is linked to poorer sleep-dependent memory performance in older adults with subjective memory complaints. The second study shows the importance of intermittent hypoxemia during REM sleep on daytime memory performance in older adults with mild cognitive impairment. The third study assessed tract-specific white matter alterations in older adults at-risk of dementia with OSA compared to without OSA. The final study examines the rates of OSA in a memory clinic using a variety of methods including self-report, sleep study, and pulse oximetry. Overall, although older people may attend memory clinics for cognitive concerns, the findings of this thesis show that memory performance is linked to sleep micro-architecture, hypoxia and to neuroimaging markers. Screening older people within the memory clinic for OSA may be, particularly if treatment for OSA in such groups can slow cognitive decline or prevent dementia.