Postdoctoral Researcher, University of Western Australia
Obstructive Sleep Apnoea (OSA) is a night-time breathing disorder within which an individual stops breathing and awakens many times per hour of sleep. This sleep and breathing disturbance is remarkably common with a prevalence of 9% in women and 27% in men, in a middle aged population. OSA is a known risk factor for diabetes, heart disease, dementia, and depression, is associated with obesity, and has a higher incidence in indigenous peoples. Addressing OSA potentially reduces the risk of a range of wide spread, high impact diseases. The disease is estimated to cost $6.6B per annum, and increases motor vehicle accidents, occupational injuries and absenteeism, and causes problems with relationships. At the heart of these vehicle, work, and social problems are disruptions to cognition. My research has clarified the picture of disruption to thinking skills in OSA, demonstrating that individuals with OSA have problems with attending to, remembering, and organising information. These thinking skills are indispensable for control and organisation of daily activity. Identifying what disruptions cause these thinking disturbances will allow for targeted therapy. My research has shown that key to these thinking disturbances is sleep disruption. Sleep disruptions in OSA play a crucial role in harming an individual’s ability to attend to, and organise information, and that the length of time an individual has had OSA, or the double burden of age and OSA, may worsen the impact on thinking skills. I am presently using a data-driven statistical technique to investigate what factors disrupt thinking skills in individuals with OSA. Some of the factors we expect this analysis to uncover are the number of comorbidities an individual with OSA, the amount of sleep disruption, the amount of time and depth of low oxygen, intelligence before developing OSA, and the length of time an individual has had OSA.
Abstract: Obstructive sleep apnoea (OSA) is a common disorder, for which continuous positive airway pressure (CPAP) therapy is a standard treatment. Despite its well-established efficacy, many patients choose not to initiate CPAP treatment. The present study investigated the degree to which biological measures (e.g. Apnoea-Hypopnoea Index [AHI]), symptom experiences (e.g. fatigue) and illness representations (e.g. perceived consequences) predict the decision of individuals newly diagnosed with OSA to undergo a trial of CPAP therapy.Four hundred forty-nine individuals (316 males) newly diagnosed with OSA. Epworth sleepiness scale (ESS), Fatigue Severity Scale, Depression Anxiety Stress Scale and Illness Perception Questionnaire-Revised (IPQ-R) were administered at time of sleep study. These, patient demographics and sleep study variables were used to determine factors predicting patient decision to proceed with a trial of CPAP.The participants were most likely to attribute their OSA to unchangeable and psychological factors. For those with moderate OSA (AHI, 15 to 30) IPQ-R illness consequence was predictive of decision to initiate CPAP (p = 0.002). For severe OSA (AHI >30) age, ESS and IPQ illness causal beliefs were predictive of decision to initiate CPAP (p < 0.001).Illness beliefs are important determinants of the choice of recently diagnosed OSA patients whether or not to undertake a trial of CPAP therapy. Concerns about illness consequences were important in those with moderate OSA. In severe OSA, sleepiness symptoms are more prominent and a more significant determinant of CPAP uptake along with age and causal beliefs.
Pub.: 22 Mar '13, Pinned: 13 Aug '17
Abstract: Obstructive sleep apnea (OSA) is a common disorder that is associated with impaired attention, memory and executive function. However, the mechanisms underlying such dysfunction are unclear. To determine the influence of sleep fragmentation and hypoxia, this study examined the effect of sleep fragmentation and hypoxia on cognition in OSA, while controlling for potentially confounding variables including sleepiness, age and premorbid intelligence.Participants with and without OSA (N = 150) were recruited from the general community and a tertiary hospital sleep clinic. All underwent comprehensive, laboratory-based polysomnography (PSG) and completed assessments of cognition including attention, short- and long-term memory and executive function. Structural equation modelling (SEM) was used to construct a theoretically-driven model to examine the relationships between hypoxia and sleep fragmentation, and cognitive function.Although after controlling for IQ, increased sleep disturbance was a significant predictor of decreased attention (p = 0.04) and decreased executive function (p = 0.05), controlling for age removes these significant relationships. No significant predictors of memory function were found.The mechanisms underlying the effects of OSA on cognition remain to be defined. Implications are discussed in light of these findings.
Pub.: 20 May '14, Pinned: 13 Aug '17
Abstract: Adult obstructive sleep apnoea (OSA) is associated with cognitive dysfunction. While many review articles have attempted to summarize the evidence for this association, it remains difficult to determine which domains of cognition are affected by OSA. This is because of marked differences in the nature of these reviews (e.g. many are unsystematic) and the many different tasks and domains assessed. This paper addresses this issue by comparing the results of only systematic reviews or meta-analyses assessing the effects of OSA on cognition, the relationship between OSA severity and cognition, and/or the effects of treatment on cognition in OSA. Electronic databases and hand-searching were undertaken to select reviews that reported on these areas. We found 33 reviews; five reviews met predetermined, stringent selection criteria. The majority of reviews supported deficits in attention/vigilance, delayed long-term visual and verbal memory, visuospatial/constructional abilities, and executive function in individuals with OSA. There is also general agreement that language ability and psychomotor function are unaffected by OSA. Data are equivocal for the effects of OSA on working memory, short-term memory and global cognitive functioning. Attention/vigilance dysfunction appears to be associated with sleep fragmentation and global cognitive function with hypoxaemia. Continuous positive airway pressure treatment of OSA appears to improve executive dysfunction, delayed long-term verbal and visual memory, attention/vigilance and global cognitive functioning. In order to improve our understanding of cognitive dysfunction in OSA, future research should pay particular attention to participant characteristics, measures of disease severity and choice of neuropsychological tests.
Pub.: 24 Aug '12, Pinned: 13 Aug '17
Abstract: Obstructive sleep apnea (OSA) is a nocturnal breathing disorder that is associated with cognitive impairment. The primary determinants of cognitive deficits in OSA are thought to be sleep disruption and blood gas abnormalities. Cognitive impairment is also seen in other disorders that are characterised primarily by sleep disturbance (e.g., sleep restriction/deprivation, insomnia) or hypoxia/hypercarbia (e.g. chronic obstructive pulmonary disease (COPD). Assessment of the cognitive defects observed in these other disorders could help better define the mechanisms underlying cognitive deficits in OSA. This study utilised meta-review methodology to examine the findings from systematic reviews and meta-analyses of the effects of untreated OSA, COPD, insomnia and sleep deprivation on cognitive function in adults, compared with norms or controls. Eighteen papers met inclusion criteria: 7 in OSA, 2 in insomnia, 5 in COPD, and 4 in sleep deprivation. OSA and COPD were both accompanied by deficits in attention, memory, executive function, psychomotor function and language abilities, suggesting that hypoxia/hypercarbia may be an important determinant of deficits in these domains in OSA. Both OSA and sleep deprivation studies were accompanied by deficits in attention and memory, suggesting that short-term sleep disturbance in OSA may contribute to deficits in these domains. Visuospatial deficits were unique to OSA, suggesting the contribution of a mechanism other than sleep disturbance and hypoxia/hypercarbia to this problem. Our findings suggest that the cognitive deficits associated with untreated OSA are multidimensional, with different physiological disturbances responsible for differing cognitive problems.
Pub.: 30 Mar '17, Pinned: 13 Aug '17
Abstract: Obstructive sleep apnea (OSA) is a frequent and often underdiagnosed condition that is associated with upper airway collapse, oxygen desaturation, and sleep fragmentation leading to cognitive dysfunction. There is meta-analytic evidence that subdomains of attention and memory are affected by OSA. However, a thorough investigation of the impact of OSA on different subdomains of executive function is yet to be conducted. This report investigates the impact of OSA and its treatment, in adult patients, on 5 theorized subdomains of executive function.An extensive literature search was conducted of published and unpublished materials, returning 35 studies that matched selection criteria. Meta-analysis was used to synthesize the results from studies examining the impact of OSA on executive functioning compared to controls (21 studies), and before and after treatment (19 studies); 5 studies met inclusion in both categories.Research papers were selected which assessed 5 subdomains of executive function: Shifting, Updating, Inhibition, Generativity, and Fluid Reasoning.All 5 domains of executive function demonstrated medium to very large impairments in OSA independent of age and disease severity. Furthermore, all subdomains of executive function demonstrated small to medium improvements with CPAP treatment.Executive function is impaired across all five domains in OSA; these difficulties improved with CPAP treatment. Age and disease severity did not moderate the effects found; however, further studies are needed to explore the extent of primary and secondary effects, and the impact of age and premorbid intellectual ability (cognitive reserve).
Pub.: 03 Sep '13, Pinned: 13 Aug '17