The impact of sleep on cognition in older adults: does depression matter?

Alix Mellor

    Research output: ThesisDoctoral Thesis

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    Abstract

    [Truncated] It is now well recognised that poor sleep affects cognition, yet this knowledge has been mostly acquired in younger or middle-aged adults. Studies in older adults are lacking, despite sleep problems and cognitive deficits with ageing being well documented. Similarly, depression has independent effects on both sleep and cognition but its impact on their relationship has been largely unexplored in older adults. The broad objectives of this thesis were to examine how sleep relates to cognition in the context of ageing and how depression impacts on this relationship. Methods of investigation included: self-reports using questionnaires, portable-polysomnography (PSG), wrist-mounted actigraphy monitoring, and neuropsychological tasks.

    The first aim of this thesis (Chapter 2) was to investigate how self-reported sleep quality changes across the lifespan, controlling for subclinical symptoms of depression and risk of sleep-disordered breathing (SDB). Participants comprised a large sample of community adults (n = 582) aged 18–89 years. Results indicate that there were modest, age-related changes in self-reported sleep quality, and that subclinical depression and SDB-risk impacted on subjective sleep quality, but did not have a marked impact on the relationship between age and sleep.

    The second aim of this thesis (Chapter 3) was to examine the pattern of association between self-reported sleep quality and cognitive complaints in a community cohort (n = 205) aged 19–89 years. Standardised questionnaires assessed subjective problems related to memory, attention, and executive functioning. Results indicate that low arousal levels (daytime effects of poor sleep) affected self-reported cognition, largely via effects on attention. In addition, depression was a significant covariate, and explained the relationship between the sleep efficiency factor and executive functioning.

    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - Jun 2014

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