Michelle Olaithe

Neurocognitive function in obstructive sleep apnoea: A meta-review

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.

Executive dysfunction in OSA before and after treatment: a meta-analysis.

STUDY OBJECTIVES 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. DESIGN 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. MEASUREMENTS Research papers were selected which assessed 5 subdomains of executive function: Shifting, Updating, Inhibition, Generativity, and Fluid Reasoning. RESULTS 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. DISCUSSION 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).

The relationship between hearing impairment and cognitive function: a meta-analysis in adults

Hearing loss affects over 1.23 billion people globally. It has been proposed that hearing impairment negatively impacts on cognition. Some studies have demonstrated a faster rate of decline in cognition, and increased risk of incident all‐cause dementia. This finding is not ubiquitous. This study used meta‐analysis to examine the evidence‐base regarding the relationship between hearing and cognition.

Cognition and nocturnal disturbance in OSA: the importance of accounting for age and premorbid intelligence

IntroductionObstructive 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.MethodParticipants 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.ResultsAlthough 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.ConclusionsThe mechanisms underlying the effects of OSA on cognition remain to be defined. Implications are discussed in light of these findings.

Embedded Figures Test Performance in the Broader Autism Phenotype: A Meta-analysis

People with autism show superior performance to controls on the Embedded Figures Test (EFT). However, studies examining the relationship between autistic-like traits and EFT performance in neurotypical individuals have yielded inconsistent findings. To examine the inconsistency, a meta-analysis was conducted of studies that (a) compared high and low Autism-Spectrum Quotient (AQ) groups, and (b) treated AQ as a continuous variable. Outcomes are consistent with superior visual search forming part of the broader autism phenotype, but in existing literature, this is evident only when comparing extreme groups. Reanalysis of data from previous studies suggests findings are unlikely to be driven by a small number of high scorers. Monte Carlo simulations are used to illustrate the effect of methodological differences on results.

Cognitive deficits in obstructive sleep apnea: Insights from a meta-review and comparison with deficits observed in COPD, insomnia, and sleep deprivation

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 deficits 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: seven in OSA, two in insomnia, five in COPD, and four 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.

Can we get more from the Epworth Sleepiness Scale (ESS) than just a single score?: a confirmatory factor analysis of the ESS

PurposeThe Epworth Sleepiness Scale (ESS) is a widely used tool for measuring sleepiness. In addition to providing a single measure of sleepiness (a one-factor structure), the ESS also has the capacity to provide additional information about specific factors that facilitate sleep onset, including a person’s posture, activity and environment. These features of sleepiness are referred to as somnificity. This study evaluates and compares the fit of a one-factor structure (sleepiness) and three-factor structure (reflecting low, medium and high levels of somnificity) for the ESS.MethodsAll participants (a community sample N = 356 and a clinical sample N = 679) were administered the ESS. Confirmatory factor analysis was used to evaluate and compare the fit of one- and three-factor models of the ESS.ResultsIn both samples, a three-factor structure (community sample adjusted X2 = 2.95, root mean square error of approximation (RMSEA) = 0.07, Comparative Fit Index (CFI) = 0.95; clinical sample adjusted X2 = 3.98, RMSEA = 0.07, CFI = 0.98) provided a level of model fit that was at least as good as the one-factor structure (community sample adjusted X2 = 5.01, RMSEA = 0.11, CFI = 0.87; clinical sample adjusted X2 = 8.87, RMSEA = 0.11, CFI = 0.92).ConclusionsIn addition to a single measure of sleepiness, the ESS can provide subscale scores which relate to three underlying levels of somnificity. These findings suggest that the ESS can be used to measure an individual’s overall sleep propensity as well as more specific measures of sleep propensity in low, moderate and high levels of situational somnificity.

Reviewing the relationship between OSA and cognition: Where do we go from here?

Obstructive sleep apnoea (OSA) is a disorder of breathing during sleep resulting in temporary reduction in cerebral oxygenation and sleep disruption. A growing body of research reveals a relatively consistent pattern of deficits in cognition, particularly in attention, episodic memory, and executive function, which are partially remediated by treatment.

Sleep and Aging: Examining the Effect of Psychological Symptoms and Risk of Sleep-Disordered Breathing

Controversy exists as to whether self-reported sleep quality declines with age, despite changes in sleep being accepted as part of normal aging. This study sought to investigate age-related differences in self-reported sleep quality, after controlling for conditions that are common with age, such as psychological symptoms and increased risk of sleep-disordered breathing (SDB). The Pittsburgh Sleep Quality Index (PSQI) was administered to a sample of 582 community adults (aged 18–89 years), and the association between age and 3 factors of the PSQI (sleep efficiency, perceived sleep quality, and daily disturbance), and global scores, was examined controlling for depression, anxiety, stress, gender, and SDB risk. Results indicate that (a) before controlling for covariates, there was no significant relation between age and all indexes of self-reported sleep quality, with the exception of sleep efficiency. However, once depression, gender, and SDB risk were controlled for, a significant, yet small, relation was revealed between older age and poorer global sleep quality; (b) there was no association between age and perceived sleep quality or daily disturbances before or after controlling for relevant covariates; and (c) depression, gender, and SDB risk were significant predictors of poorer sleep quality across the indexes but, in general, did not have a marked impact on the relation between age and sleep quality. In conclusion, results suggest that sleep problems are common across the lifespan, and that there were modest age-related differences in self-reported sleep quality, which were not due to depressed mood, gender, or risk of SDB.

Predicting uptake of continuous positive airway pressure (CPAP) therapy in obstructive sleep apnoea (OSA): a belief-based theoretical approach

PurposeObstructive 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.MethodsFour 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.ResultsThe 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).ConclusionsIllness 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.