Obstructive sleep apnoea and cognitive impairment in older adults

Lee, V 2019, Obstructive sleep apnoea and cognitive impairment in older adults, Doctor of Philosophy (PhD), Health and Biomedical Sciences, RMIT University.


Document type: Thesis
Collection: Theses

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Title Obstructive sleep apnoea and cognitive impairment in older adults
Author(s) Lee, V
Year 2019
Abstract Obstructive sleep apnoea (OSA) has been linked to several neuropsychological deficits, such as attention and executive functioning deficits, and memory impairment. Recently, OSA has been identified as a risk factor for the development of mild cognitive impairment (MCI)/dementia. Given the reported association between OSA and cognitive decline, identifying the potential mechanisms can have important implications for early detection and risk assessment. Identification of cognitive areas affected by OSA is also important as it allows the possibility of an intervention that targets the sleep-related factors that may be contributing towards the development of cognitive impairment. The broad aim of this thesis was to examine the relationship between cognition and obstructive sleep apnoea in older adults with and without comorbid MCI.

The first study of the thesis consists of two parts and both aimed to investigate specific autobiographical memory impairment in OSA patients. While our previous study (Lee, Trinder & Jackson, 2016) reported impairment in specific autobiographical memory recall in OSA patients, we also reported that age may be a potential confounding factor. Accordingly, the first aim was to expand our previous work and investigate if there is an age-related effect on specific autobiographical memory impairment in OSA patients. Specific autobiographical memory performance was compared between four groups: (i) 20 young healthy controls (<50 years); (ii) 20 young OSA patients (<50 years); (iii) 19 older healthy controls (≥50 years); and (iv) 18 older OSA patients (≥50 years). Results indicated that all OSA patients performed significantly worse than healthy controls and young OSA patients are as impaired as older OSA patients in specific autobiographical memory recall.

Secondly, specific autobiographical memory impairment has been reported in OSA and MCI patients independently. Given the high comorbidity between OSA and MCI patients, it is yet unknown if this specific autobiographical memory impairment observed in individuals with clinically significant cognitive decline can be attributed to sleep apnoea. Accordingly, the second part of this study aimed to assess specific autobiographical memory performance in patients with comorbid OSA and MCI in comparison to OSA with no significantly cognitive impairment and healthy controls. In this part, specific autobiographical memory performance was compared between three groups (i) 18 OSA patients with comorbid MCI; (ii) 19 age-matched OSA patients; and (iii) 19 aged-matched healthy controls. The results revealed that OSA patients without clinically significant cognitive impairment performed as poorly as OSA patients with MCI in specific autobiographical memory recall.

Following on from the first study, the second study continued the investigation of cognitive impairment in patients with comorbid OSA and MCI. The majority of studies that examined cognitive impairment in patients with comorbid OSA and MCI/dementia have mainly focused on global cognition. Given the known impairments of different cognitive domains in OSA patients, limited studies have examined the relationship between specific cognitive domains and sleep apnoea in patients with comorbid OSA and MCI. Accordingly, the second study aimed to examine the relationship between sleep apnoea severity and cognitive performance in patients with comorbid OSA and MCI. To examine the potential underlying mechanisms of this relationship, this portion of the thesis was also interested in exploring the relationship between cognitive performance and the different aspects of sleep apnoea, including intermittent hypoxia, sleep fragmentation, sleep architecture and subjective sleep measures. Also, the study compared cognitive performance and mood between MCI patients with and without OSA in a subset of cognitive domains.

Eighteen OSA patients with MCI completed a neuropsychological test-battery including measures of global cognition, verbal memory, visual memory, working memory, processing speed and attention, and executive function. Results indicated that higher sleep apnoea severity was significantly associated with poorer global cognition and working memory. Further analyses showed that cognitive performance was significantly linked with measures of intermittent hypoxia and percentage of time spent in slow wave sleep (SWS) but not measures of sleep fragmentation, subjective daytime sleepiness and subjective sleep quality. Finally, the between group comparison demonstrated that MCI patients with OSA had significantly more anxiety symptoms, and poorer processing speed when compared to MCI patients without OSA, or with age-matched healthy controls.

Finally, study three aimed to investigate the efficacy of three months of CPAP therapy on cognitive performance and mood in patients with comorbid OSA and MCI. Recent findings from Osorio and colleagues (2015) reported that individuals at an earlier stage of cognitive impairment may benefit the most from CPAP use, and that CPAP therapy has the potential to slow down the age of onset in MCI patients. While several CPAP trial studies have been conducted with patients with Alzheimer's disease, limited studies have examined the effects of CPAP therapy on cognitive performance and mood in MCI patients. In this study, eight OSA patients with MCI received three months of CPAP therapy. Prior to starting CPAP and again after three months of treatment, participants completed a 90-minute neuropsychological test battery, and a set of mood and sleep questionnaires. The results indicated that three months of CPAP therapy in this patient population have the potential to improve daytime sleepiness, global cognitive, logical memory and specific autobiographical memory.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Health and Biomedical Sciences
Subjects Psychology not elsewhere classified
Keyword(s) Obstructive sleep apnoea
Cognition
Cognitive impairment
Older adults
Continuous positive airway pressure therapy
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Created: Mon, 30 Sep 2019, 11:57:08 EST by Adam Rivett
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