Information processing speed in obstructive sleep apnea syndrome: a review

Verbal memory is linked to average oxygen saturation during sleep, not the apnea-hypopnea index nor novel hypoxic load variables

INTRODUCTION

The apnea-hypopnea index (AHI) is the current diagnostic parameter for diagnosing and estimating the severity of obstructive sleep apnea (OSA). It is, however, poorly associated with the main clinical symptom of OSA, excessive daytime sleepiness, and with the often-seen cognitive decline among OSA patients. To better evaluate OSA severity, novel hypoxic load parameters have been introduced that consider the duration and depth of oxygen saturation drops associated with apneas or hypopneas. The aim of this paper was to compare novel hypoxic load parameters and traditional OSA parameters to verbal memory and executive function in OSA patients.

METHOD

A total of 207 adults completed a one-night polysomnography at sleep laboratory and two neuropsychological assessments, the Rey Auditory Verbal Learning Test and Stroop test.

RESULTS

Simple linear regression analyses were used to evaluate independent associations between each OSA parameter and cognitive performance. Associations were found between immediate recall and arousal index, hypoxia <90 %, average SpO2 during sleep, and DesSev100+RevSev100. Total recall was associated with all OSA parameters, and no associations were found with the Stroop test. Subsequently, sex, age, and education were included as covariates in multiple linear regression analyses for each OSA parameter and cognitive performance. The main findings of the study were that average SpO2 during sleep was a significant predictor of total recall (p < .007, β = -.188) with the regression model explaining 21.2 % of performance variation. Average SpO2 during sleep was also a significant predictor of immediate recall (p < .022, β = -.171) with the regression model explaining 11.4 % of performance variation. Neither traditional OSA parameters nor novel hypoxic load parameters predicted cognitive performance after adjustment for sex, age, and education.

CONCLUSION

The findings validate that the AHI is not an effective indicator of cognitive performance in OSA and suggest that average oxygen saturation during sleep may be the strongest PSG predictor of cognitive decline seen in OSA. The results also underline the importance of considering age when choosing neurocognitive tests, the importance of including more than one test for each cognitive domain as most tests are not pure measures of a single cognitive factor, and the importance of including tests that cover all cognitive domains as OSA is likely to have diffuse cognitive effects.

Impact of continuous positive airway pressure on cognitive functions in adult patients with obstructive sleep apnea: A systematic review and meta-analysis

BACKGROUND

Obstructive sleep apnea (OSA) is associated with the impairment of a range of cognitive functions. Whether treatment with continuous positive airway pressure (CPAP) improves these cognitive functions is still a matter of debate.

METHODS

We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) that included OSA patients (apnea hypopnea index, AHI >10/h), naive to CPAP treatment, with a cognitive assessment before and after CPAP initiation. We compared CPAP versus sham-CPAP or placebo tablet or dietary rules or no treatment. This systematic review and meta-analysis were registered in PROSPERO (ID CRD42021275214).

RESULTS

Eleven RCTs encompassing 923 OSA patients were included. For most of them, CPAP initiation was ≤3 months. A significant post-treatment improvement was found for the Trail Making Test part B (TMT-B; SMD = -0.93, 95 % CI = [-1.60, -0.25], Z = -2.70, p = 0.007), but not for the other neuropsychological assessments. No global effects on other cognitive domains (information processing speed, executive functions, working memory) were found.

CONCLUSION

The significant improvement in the TMT-B supports a short-term enhancement in cognitive flexibility with CPAP treatment. Further studies that take into account OSA comorbidities, cognitive profiles, a more diverse range of cognition assessments and include long-term evaluations are needed.

Impact of sleep disturbance in shift workers on hippocampal volume and psychomotor speed

STUDY OBJECTIVES

Shift work interferes with circadian rhythms, affecting sleep quality and cognitive function. Poor sleep quality in shift worker (SW)s can impair psychomotor performance due to fatigue and sleepiness, increasing the risk of errors, accidents, and reduced productivity. Given the potential for atrophic changes in the hippocampus due to sleep disturbances, our study investigates how poor sleep quality correlates with hippocampal structural alterations and impacts psychomotor performance among SWs.

METHODS

We recruited 100 SWs, classifying them based on sleep quality into two groups: good sleep-SW group (n = 59) and poor sleep-SW group (n = 41). Sleep quality was assessed using both 7-day actigraphy for sleep efficiency and the Pittsburgh Sleep Quality Index. A control group of 106 non-SWs without sleep problems (non-SW group) was also included for comparison. The outcome measures were psychomotor speed and hippocampal volumes, both total and by subfield.

RESULTS

The poor sleep-SW group showed significantly smaller hippocampal volumes than both the good sleep-SW group (p < .001) and the non-SW group (p = .003). Longer shift work years correlated with greater reductions in hippocampal volume in this group (r = -0.42, p = .009), unlike in the good sleep-SW group (r = 0.08, p = .541). Furthermore, they demonstrated declines in psychomotor speed relative to the non-SW group (p = .006), which correlated with smaller hippocampal volumes (r = 0.37, p = .020).

CONCLUSIONS

SWs with poor sleep quality exhibit significant hippocampal volume reductions and psychomotor speed decline, underscoring the importance of early intervention and support for sleep issues in this population.

Excessive daytime sleepiness in young and middle-aged Chinese adults with obstructive sleep apnea: implications for cognitive dysfunction

OBJECTIVE

The objective of this study was to investigate the effects of excessive daytime sleepiness (EDS) on cognitive function among Chinese young and middle-aged Chinese patients with obstructive sleep apnea (OSA).

METHODS

Chinese adults struggling from moderate to severe OSA with apnea-hypopnea index (AHI) ≥ 15 events per hour and adults with primary snoring and mild OSA (AHI < 15 events per hour) were included in the study. The Epworth Sleepiness Scale measured hypersomnia, and cognitive function was assessed using the Mini-mental State Examination (MMSE) and Montreal Cognitive Assessment (MOCA).

RESULTS

In comparison to the primary snoring and mild OSA group (n=635), the moderate to severe OSA group (n=1423) tended to be older men with higher scores on the Epworth Sleepiness Scale (ESS), as well as higher levels of oxygen desaturation (ODI) and a higher body mass index (BMI). Patients with moderate to severe OSA had fewer years of education, lower minimum arterial oxygen saturation (min-SaO2), and more severe sleep disturbances, such as decreased slow wave sleep (SWS) and rapid eye movement (REM) and increased non-REM stages (N1 and N2). Comorbid conditions such as hypertension and diabetes mellitus were more common in these patients (P < 0.01 and P < 0.05, accordingly). Only the delayed recall scores were statistically lower in the moderate to severe OSA group than the primary snoring and mild OSA group (P < 0.05). The main factor associated with delayed recall was the ESS score rather than age or years of education among moderate-severe OSA patients ≤ 40 years of age (P < 0.05). After controlling for potential confounding factors such as age, gender, BMI, education, hypertension, diabetes, sleep stages (SWS and REM), minimum arterial oxygen saturation (min-SaO2), oxygen ODI, and AHI, there was a negative correlation between the Epworth Sleepiness Scale (ESS) score and the delayed recall scores.

CONCLUSION

Patients with moderate to severe OSA had cognitive dysfunction, particularly impairment of delayed recall. Excessive daytime sleepiness (EDS) was significantly associated with cognitive dysfunction in young and middle-aged patients with OSA.

Cognitive and emotional predictors of quality of life and functioning after COVID-19

OBJECTIVE

A long-term decline in health-related quality of life (HRQoL) has been reported after coronavirus disease 2019 (COVID-19). Studies with people with persistent symptoms showed inconsistent outcomes. Cognition and emotion are important determinants in HRQoL, but few studies have examined their prognostic significance for HRQoL and functionality in post-COVID patients with persisting symptoms. We aimed to describe QoL, HRQoL, and functioning in individuals post-COVID with varying COVID-19 severities and to investigate the predictive value of cognitive and emotional variables for QoL, HRQoL, and functioning.

METHODS

In total, 492 participants (398 post-COVID and 124 healthy controls) underwent a neurobehavioral examination that included assessments of cognition, mood, QoL/HRQoL (WHOQOL-BREF, EQ-5D), and functioning (WHODAS-II). Analysis of covariance and linear regression models were used to study intergroup differences and the relationship between cognitive and emotional variables and QoL and functioning.

RESULTS

The Physical and Psychological dimensions of WHOQoL, EQ-5D, and WHODAS Cognition, Mobility, Life Activities, and Participation dimensions were significantly lower in post-COVID groups compared with a control group. Regression models explaining 23.9%-53.9% of variance were obtained for the WHOQoL-BREF dimensions and EQ-5D, with depressive symptoms, post-COVID symptoms, employment status, income, and mental speed processing as main predictors. For the WHODAS, models explaining 17%-60.2% of the variance were obtained. Fatigue, depressive symptoms, mental speed processing, and post-COVID symptoms were the main predictors.

INTERPRETATION

QoL/HRQoL and functioning after COVID-19 in individuals with persistent symptoms were lower than in non-affected persons. Depressive symptoms, fatigue, and slower mental processing speed were predictors of lower QoL/HRQoL and functioning.

International Consensus Statement on Obstructive Sleep Apnea

BACKGROUND

Evaluation and interpretation of the literature on obstructive sleep apnea (OSA) allows for consolidation and determination of the key factors important for clinical management of the adult OSA patient. Toward this goal, an international collaborative of multidisciplinary experts in sleep apnea evaluation and treatment have produced the International Consensus statement on Obstructive Sleep Apnea (ICS:OSA).

METHODS

Using previously defined methodology, focal topics in OSA were assigned as literature review (LR), evidence-based review (EBR), or evidence-based review with recommendations (EBR-R) formats. Each topic incorporated the available and relevant evidence which was summarized and graded on study quality. Each topic and section underwent iterative review and the ICS:OSA was created and reviewed by all authors for consensus.

RESULTS

The ICS:OSA addresses OSA syndrome definitions, pathophysiology, epidemiology, risk factors for disease, screening methods, diagnostic testing types, multiple treatment modalities, and effects of OSA treatment on multiple OSA-associated comorbidities. Specific focus on outcomes with positive airway pressure (PAP) and surgical treatments were evaluated.

CONCLUSION

This review of the literature consolidates the available knowledge and identifies the limitations of the current evidence on OSA. This effort aims to create a resource for OSA evidence-based practice and identify future research needs. Knowledge gaps and research opportunities include improving the metrics of OSA disease, determining the optimal OSA screening paradigms, developing strategies for PAP adherence and longitudinal care, enhancing selection of PAP alternatives and surgery, understanding health risk outcomes, and translating evidence into individualized approaches to therapy.

Cognitive Functions, Depressive and Anxiety Symptoms After One Year of CPAP Treatment in Obstructive Sleep Apnea

Objective

The study worked with depressive symptoms, anxiety score and cognitive functions in obstructive sleep apnea (OSA) patients treated with CPAP.

Methods

Eighty-one subjects with OSA and without psychiatric comorbidity were treated with CPAP for one year and completed the following scales and cognitive tests: Trail Making Test, Verbal Fluency Test, d2 Test, Beck Depression Inventory-II and Beck Anxiety Inventory. MINI ruled out psychiatric disorder. At the two months check-up, subjects were re-evaluated for depressive and anxiety symptoms, and after one year of CPAP treatment, subjects repeated cognitive tests and scales. Data about therapy adherence and effectiveness were obtained from the patient's CPAP machines.

Results

The study was completed by 59 CPAP adherent patients and eight non-adherent patients. CPAP therapy effectiveness was verified in all patients by decreasing the apnea-hypopnoea index below 5 and/or 10% of baseline values. The adherent patients significantly improved depressive and anxiety symptoms. There was also an improvement in overall performance in the attention test; however, performance in many individual items did not change. The adherent patients also improved verbal fluency and in the Part B of the Trail making test. The non-adherent group significantly increased the number of mistakes made in the d2 test; other results were non-significant.

Conclusion

According to our results, OSA patients' mood, anxiety and certain cognitive domains improved during the one-year therapy with CPAP.

Trial Registration Number

NCT03866161.

Mentation Tracks Severity but not Oxygenation in Obstructive Sleep Apnea

There is a rough consensus, after decades of research, that obstructive sleep apnea (OSA) is associated with mild cognitive impairments, especially in areas of executive functioning (EF), attention/working memory (A/WM), episodic memory (EM), and speed of speed of information processing (SIP). However, there is less consensus as to whether apnea severity matters for these impairments, which sleep variables matter most to which cognitive domains, whether common OSA comorbidities contribute to these determinations, or whether the apparent associations are really artifacts of these comorbidities. In this study, 40 participants with OSA submitted to polysomnography and to neuropsychological assessment with an expanded Halstead-Reitan Test Battery. Aggregates of tests to cover the four cognitive domains mentioned above were linearly regressed on the apnea-hypopnea index (AHI), the nadir of oxygen saturation (NOS), and hypertension and diabetes mellitus (scored present or absent). The AHI predicted both EF (p = .015; sr2 = .13) and A/WM (p = .023; sr2 = 11) in the primary analyses, and EM (p = .027; sr2 = .10) in the secondary analyses. Thus, AHI may affect EF, A/WM and perhaps EM beyond NOS and beyond two of OSA's most common comorbidities. Implications of these findings are discussed here.

Eye-to-Hand Coordination in Obstructive Sleep APNEA Syndrome: a Descriptive Study

OBJECTIVE

Psychomotor slowdown was observed in individuals with Obstructive Sleep Apnea Syndrome (OSAS). Previous studies evaluated separately cognitive and motor reaction times, finding that OSAS individuals show a specific impairment in the latter. The present study investigates whether eye-to-hand coordination (EHC), a specific psychomotor ability, is compromised in OSAS.

METHOD

The EHC was measured in 30 OSAS individuals who were matched with 30 healthy controls by the Two-Hand Coordination Test analyzing the speed, accuracy, and coordination; the role of these variables was investigated in predicting the group they belonged to.

RESULTS

The OSAS participants showed poorer performance in the execution accuracy (t(55) = -3.36, d'Cohen = -0.89, p ≤ .001), which was also found to be the only predictor of the belonging to group (β = 0.43 (0.18), p < .05).

CONCLUSIONS

The OSAS individuals show impairments in EHC and in correcting their error (executive slowdown). This is the first investigation exploring EHC coordination in this population and contributes in understanding the psychomotor slowness characterizing OSAS.

Contribution of hypercapnia to cognitive impairment in severe sleep-disordered breathing

STUDY OBJECTIVES

Although cognitive impairment in obstructive sleep apnea (OSA) is primarily attributed to intermittent hypoxemia and sleep fragmentation, hypercapnia may also play a role in patients whose OSA is complicated by hypoventilation. This study investigated the impact of hypercapnia on cognitive function in severe sleep-disordered breathing (OSA accompanied by hypoventilation).

METHODS

Patients with severe OSA (apnea-hypopnea index >30 events/h; n = 246) underwent evaluation for accompanying hypoventilation with polysomnography that included continuous transcutaneous carbon dioxide (TcCO₂) monitoring and awake arterial blood gas analysis. Patients were categorized as having no hypoventilation (n = 84), isolated sleep hypoventilation (n = 40), or awake hypoventilation (n = 122). Global cognitive function was evaluated using the Montreal Cognitive Assessment (MoCA), memory with the Rey Auditory Verbal Learning Test (RAVLT), and processing speed with the Wechsler Adult Intelligence Scale, Fourth Edition (WAIS-IV), Digit Symbol Coding subtest (DSC).

RESULTS

Apnea-hypopnea index was similar across groups (P = .15), but the sleep and awake hypoventilation groups had greater nocturnal hypoxemia compared with the no-hypoventilation group (P < .01). Within all groups, mean MoCA scores were < 26, which is the validated threshold to indicate mild cognitive impairment; RAVLT scores were lower than age-matched norms only in the awake-hypoventilation group (P ≤ .01); and DSC scores were lower than age-matched norms within all groups (P < .01). In multivariable regression analyses, higher arterial partial pressure of carbon dioxide (PaCO₂) and TcCO₂ during wakefulness were associated with lower MoCA and DSC scores (P ≤ .03), independent of confounders including overlap syndrome (OSA + chronic obstructive pulmonary disease).

CONCLUSIONS

Awake hypoventilation is associated with greater deficits in cognitive function in patients with severe sleep-disordered breathing.

CITATION

Beaudin AE, Raneri JK, Ayas NT, Skomro RP, Smith EE, Hanly PJ; on behalf of Canadian Sleep and Circadian Network. Contribution of hypercapnia to cognitive impairment in severe sleep-disordered breathing. J Clin Sleep Med. 2022;18(1):245-254.

Objective Measures of Cognitive Performance in Sleep Disorder Research

Neurocognitive tests offer objective and reliable assessment of patients' status and progress. However, there is no consensus on how to use neurocognitive assessment in sleep disorder research. An effective use of neurocognitive assessment must be based on standardized practices and have a firm theoretic basis. The aim of this review is to offer an overview of how different tests have been used in the field, mapping each test onto a corresponding cognitive domain and propose how to move forward with a suggested cognitive battery of tests covering all major cognitive domains.

Cognitive Function in a Sleep Clinic Cohort of Patients with Obstructive Sleep Apnea

Rationale: Obstructive sleep apnea (OSA) is associated with an increased risk of mild cognitive impairment (MCI) within the general population. However, MCI risk in sleep-clinic populations of patients with OSA is poorly characterized.Objectives: To determine the prevalence of MCI in a sleep-clinic population of patients with OSA and which patients are at the greatest risk for this complication.Methods: Adults (n = 1,084) referred to three academic sleep centers for suspected OSA who had home sleep apnea testing or in-laboratory polysomnography were recruited. Patients completed sleep and medical history questionnaires, the Montreal Cognitive Assessment Test (MoCA) of global cognition, the Rey Auditory Verbal Learning Test of memory, and the Wechsler Adult Intelligence Scale-Fourth Edition Digit-Symbol Coding (DSC) subtest of information processing speed.Results: A MoCA score <26 (range 0-30) was operationally defined as MCI. MCI was present in 47.9% of our entire patient cohort, increasing to >55.3% in patients with moderate and severe OSA. Patients with a MoCA <26 were predominantly older males with more severe OSA, hypoxemia, and vascular comorbidities. Moderate and severe OSA were independently associated with >70% higher odds for MCI compared with patients with no OSA (P = 0.003). Memory and information processing speed was lower than age-matched normal values (P < 0.001), with lower MoCA and DSC scores associated with a higher oxygen desaturation index and nocturnal hypoxemia.Conclusions: Cognitive impairment is highly prevalent in patients referred to sleep clinics for suspected OSA, occurring predominantly in older males with moderate to severe OSA and concurrent vascular comorbidities. Moderate to severe OSA is an independent risk factor for MCI.

The Importance of Diagnosing and the Clinical Potential of Treating Obstructive Sleep Apnea to Delay Mild Cognitive Impairment and Alzheimer's Disease: A Special Focus on Cognitive Performance

Obstructive sleep apnea (OSA) is a highly frequent sleep disorder in the middle-aged and older population, and it has been associated with an increased risk of developing cognitive decline and dementia, including mild cognitive impairment (MCI) and Alzheimer's disease (AD). In more recent years, a growing number of studies have focused on: 1) the presence of OSA in patients with MCI or AD, 2) the link between OSA and markers of AD pathology, and 3) the role of OSA in accelerating cognitive deterioration in patients with MCI or AD. Moreover, some studies have also assessed the effects of continuous positive airway pressure (CPAP) treatment on the cognitive trajectory in MCI and AD patients with comorbid OSA. This narrative review summarizes the findings of studies that analyzed OSA as a risk factor for developing MCI and/or AD in the middle-aged and older populations with a special focus on cognition. In addition, it describes the results regarding the effects of CPAP treatment in hampering the progressive cognitive decline in AD and delaying the conversion to AD in MCI patients. Considering the importance of identifying and treating OSA in patients with MCI or AD in order to prevent or reduce the progression of cognitive decline, further larger and adequately powered studies are needed both to support these findings and to set programs for the early recognition of OSA in patients with cognitive impairment.

Characterization of the abnormal cortical effective connectivity in patients with sleep apnea hypopnea syndrome during sleep

BACKGROUND AND OBJECTIVES

Sleep apnea hypopnea syndrome (SAHS) is a prevalent sleep breathing disorder that can lead to brain damage and is also a risk factor for cognitive impairment and some common diseases. Studies on cortical effective connectivity (EC) during sleep may provide more direct and pathological information and shed new light on brain dysfunction due to SAHS. However, the EC is rarely explored in SAHS patients, especially during different sleep stages.

METHODS

To this end, six-channel EEG signals of 43 SAHS patients and 41 healthy participants were recorded by whole-night polysomnography (PSG). The symbolic transfer entropy (STE) was applied to measure the EC between cortical regions in different frequency bands. Posterior-anterior ratio (PA) was employed to evaluate the posterior-to-anterior pattern of information flow based on overall cortical EC. The statistical characteristics of the STE and PA and of the intra-individual normalized parameters (STE* and PA*) were served as different feature sets for classifying the severity of SAHS.

RESULTS

Although the patterns of STE across electrodes were similar, significant differences were found between the patient and the control groups. The variation trends across stages in the PA were also different in multiple frequency bands between groups. Important features extracted from the STE* and PA* were distributed in multiple rhythms, mainly in δ, α, and γ. The PA* feature set gave the best results, with accuracies of 98.8% and 83.3% for SAHS diagnosis (binary) and severity classification (four-way).

CONCLUSIONS

These results suggest that modifications in cortical EC were existed in SAHS patients during sleep, which may help characterize cortical abnormality in patients.

Sleep-disordered breathing and the risk of Alzheimer's disease

Sleep-disordered breathing is highly prevalent in the elderly population. Obstructive sleep apnea (OSA) represents the most common sleep disorder among the adult and elderly population. Recently, OSA diagnosis has been associated with an increased risk of developing cognitive decline and dementia, including vascular dementia and Alzheimer's disease (AD). Subsequently, there have been studies on AD biomarkers investigating cerebrospinal fluid, blood, neuroimaging, and nuclear medicine biomarkers in patients with OSA. Furthermore, studies have attempted to assess the possible effects of continuous positive airway pressure (CPAP) treatment on the cognitive trajectory and AD biomarkers in patients with OSA. This review summarizes the findings of studies on each AD biomarker (cognitive, biofluid, neuroimaging, and nuclear medicine imaging) in patients with OSA, also accounting for the related effects of CPAP treatment. In addition, the hypothetical model connecting OSA to AD in a bi-directional interplay is analyzed. Finally, the sex-based differences in prevalence and clinical symptoms of OSA between men and women have been investigated in relation to AD risk. Further studies investigating AD biomarkers changes in patients with OSA and the effect of CPAP treatment should be auspicated in future for identifying strategies to prevent the development of AD.

Waking EEG functional connectivity in middle-aged and older adults with obstructive sleep apnea

OBJECTIVES

The present study aimed at investigating changes in waking electroencephalography (EEG), most specifically regarding spectral power and functional connectivity, in middle-aged and older adults with obstructive sleep apnea (OSA). We also explored whether changes in spectral power or functional connectivity are associated with polysomnographic characteristics and/or neuropsychological performance.

METHODS

In sum, 19 OSA subjects (apnea-hypopnea index ≥ 20, age: 63.6 ± 6.4) and 22 controls (apnea-hypopnea index ≤ 10, age: 63.6 ± 6.7) underwent a full night of in-laboratory polysomnography (PSG) followed by a waking EEG and a neuropsychological assessment. Waking EEG spectral power and imaginary coherence were compared between groups for all EEG frequency bands and scalp regions. Correlation analyses were performed between selected waking EEG variables, polysomnographic parameters and neuropsychological performance.

RESULTS

No group difference was observed for EEG spectral power for any frequency band. Regarding the imaginary coherence, when compared to controls, OSA subjects showed decreased EEG connectivity between frontal and temporal regions in theta and alpha bands as well as increased connectivity between frontal and parietal regions in delta and beta 1 bands. In the OSA group, these changes in connectivity correlated with lower sleep efficiency, lower total sleep time and higher apnea-hypopnea index. No relationship was found with neuropsychological performance.

CONCLUSIONS

Contrary to spectral power, imaginary coherence was sensitive enough to detect changes in brain function in middle-aged and older subjects with OSA when compared to controls. Whether these changes in cerebral connectivity predict cognitive decline needs to be investigated longitudinally.

One Year of Continuous Positive Airway Pressure Adherence Improves Cognition in Older Adults With Mild Apnea and Mild Cognitive Impairment

BACKGROUND

Mild cognitive impairment frequently represents a predementia stage of Alzheimer's disease. Although obstructive sleep apnea is increasingly recognized as a common comorbidity of mild cognitive impairment, most apnea research has focused on middle-aged adults with moderate-to-severe obstructive sleep apnea. Mild obstructive sleep apnea, defined as 5-14 apneas or hypopneas per hour slept, is common in older adults. Little is known about the effect on cognition of adherence to continuous positive airway pressure (CPAP) treatment of obstructive sleep apnea in older adults with mild obstructive sleep apnea and mild cognitive impairment.

OBJECTIVE

The objective of this study was to explore the effect of CPAP adherence on cognition in older adults with mild obstructive sleep apnea and mild cognitive impairment.

METHODS

We conducted a secondary analysis of data from Memories 1, a 1-year quasiexperimental clinical trial on the effect of CPAP adherence in older adults with mild cognitive impairment and obstructive sleep apnea. Those with mild obstructive sleep apnea were divided into two groups based on their CPAP adherence over 1 year: (a) CPAP adherent group (mild cognitive impairment + CPAP) with an average CPAP use of ≥4 hours per night and (b) CPAP nonadherent group (mild cognitive impairment - CPAP) with an average CPAP use of <4 hours per night. Individuals currently using CPAP were not eligible. A CPAP adherence intervention was provided for all participants, and an attention control intervention was provided for participants who chose to discontinue CPAP use during the 1-year follow-up. Descriptive baseline analyses, paired t tests for within-group changes, and general linear and logistic regression models for between-group changes were conducted.

RESULTS

Those in the mild cognitive impairment + CPAP group compared to the mild cognitive impairment - CPAP group demonstrated a significant improvement in psychomotor/cognitive processing speed, measured by the Digit Symbol Coding Test. Eight participants improved on the Clinical Dementia Rating Scale, whereas six worsened or were unchanged. Twelve participants rated themselves as improved on the Alzheimer's Disease Cooperative Study-Clinical Global Impression of Change Scale, whereas three reported their status as worsened or unchanged. The mild cognitive impairment + CPAP group had greater than an eightfold increased odds of improving on the Clinical Dementia Rating and greater than a ninefold increased odds of improving on the Alzheimer's Disease Cooperative Study-Clinical Global Impression of Change Scale, compared to the mild cognitive impairment - CPAP group.

DISCUSSION

CPAP adherence may be a promising intervention for slowing cognitive decline in older adults with mild obstructive sleep apnea and mild cognitive impairment. A larger, adequately powered study is needed.

Performance of facial expression classification tasks in patients with obstructive sleep apnea

STUDY OBJECTIVES

People show a facial recognition speed advantage, termed positive classification advantage (PCA), when judging whether a facial expression is happy compared to angry or sad. This study investigated emotional face recognition by patients with obstructive sleep apnea (OSA) with impaired neurocognition.

METHODS

Thirty-four patients with OSA and 26 healthy control patients who underwent 1 night of polysomnographic evaluation before recruitment were asked to complete an emotion recognition task. Accuracy rates and reaction times were recorded and analyzed using repeated-measures analysis of variance.

RESULTS

When participants were asked to classify positive (happy) versus negative (sad) emotional expressions, the phenomenon of PCA disappeared. Importantly, however, compared with the control patients who showed PCA, patients with OSA identified sad faces faster but were similar in processing happy faces.

CONCLUSIONS

In accordance with previous studies that showed depressive emotion in patients with OSA, our results indicate that patients with OSA show negative bias in facial expression recognition, which might lead to decline in ability of social communication.

Psychomotor Performance in Patients with Obstructive Sleep Apnea Syndrome

PURPOSE

Determinants of obstructive sleep apnea (OSA) are hypoxemia and hypercapnia, as well as (micro) arousals from sleep, resulting in chronic sleep fragmentation, sleep deprivation, and excessive daytime sleepiness (EDS). All of the above-mentioned factors might contribute to psychomotor impairment seen in OSA patients. Additionally, this study aimed to assess the contribution of BMI, age, EDS assessed with Epworth sleepiness scale (ESS), and severity of OSA assessed with apnea-hypopnea index (AHI) to the reaction time on chronometric tests in OSA patients and controls. It is hypothesized that moderate and severe OSA have adverse effects on reaction time of perception to visual stimulus, of solving simple arithmetic operations, and of psychomotor limbs coordination assessed by chronometric psychodiagnostic test battery.

PATIENTS AND METHODS

This study was conducted on 206 male participants; 103 of them had moderate or severe OSA diagnosed by whole-night polysomnography/polygraphy. Control participants (N=103), matched to patients with OSA by age and BMI, had no reported OSA in their medical history, no increased risk for OSA, nor EDS. All participants were assessed with three chronometric psychodiagnostic tests, measuring the reaction time of perception to visual stimulus, of solving simple arithmetic operations, and of psychomotor limbs coordination.

RESULTS

Participants from the OSA group achieved impaired results compared to control participants in minimum single task solving time in speed of solving simple arithmetic operations (3±0.9 and 2.6±0.6, P<0.001), and in minimum solving time of a single task in complex psychomotor limbs coordination (0.69±0.2 and 0.61±0.1, P=0.007). Regression analysis revealed no significant contribution of daytime sleepiness to the results achieved in each of the tests.

CONCLUSION

It is concluded that severe OSA impaired speed of perception, convergent, and operative thinking. Moreover, it is suggested that EDS did not contribute to poor psychomotor outcome in patients with OSA in this study, when age was controlled for.

Obstructive sleep apnea, cognition and Alzheimer's disease: A systematic review integrating three decades of multidisciplinary research

Increasing evidence links cognitive-decline and Alzheimer's disease (AD) to various sleep disorders, including obstructive sleep apnea (OSA). With increasing age, there are substantial differences in OSA's prevalence, associated comorbidities and phenotypic presentation. An important question for sleep and AD researchers is whether OSA's heterogeneity results in varying cognitive-outcomes in older-adults compared to middle-aged adults. In this review, we systematically integrated research examining OSA and cognition, mild cognitive-impairment (MCI) and AD/AD biomarkers; including the effects of continuous positive airway pressure (CPAP) treatment, particularly focusing on characterizing the heterogeneity of OSA and its cognitive-outcomes. Broadly, in middle-aged adults, OSA is often associated with mild impairment in attention, memory and executive function. In older-adults, OSA is not associated with any particular pattern of cognitive-impairment at cross-section; however, OSA is associated with the development of MCI or AD with symptomatic patients who have a higher likelihood of associated disturbed sleep/cognitive-impairment driving these findings. CPAP treatment may be effective in improving cognition in OSA patients with AD. Recent trends demonstrate links between OSA and AD-biomarkers of neurodegeneration across all age-groups. These distinct patterns provide the foundation for envisioning better characterization of OSA and the need for more sensitive/novel sleep-dependent cognitive assessments to assess OSA-related cognitive-impairment.

Sleep Biomarkers, Health Comorbidities, and Neurocognition in Obstructive Sleep Apnea

OBJECTIVES

Obstructive sleep apnea (OSA) is associated with cognitive impairment but the relationships between specific biomarkers and neurocognitive domains remain unclear. The present study examined the influence of common health comorbidities on these relationships. Adults with suspected OSA (N=60; 53% male; M age=52 years; SD=14) underwent neuropsychological evaluation before baseline polysomnography (PSG). Apneic syndrome severity, hypoxic strain, and sleep architecture disturbance were assessed through PSG.

METHODS

Depression (Center for Epidemiological Studies Depression Scale, CESD), pain, and medical comorbidity (Charlson Comorbidity Index) were measured via questionnaires. Processing speed, attention, vigilance, memory, executive functioning, and motor dexterity were evaluated with cognitive testing. A winnowing approach identified 9 potential moderation models comprised of a correlated PSG variable, comorbid health factor, and cognitive performance.

RESULTS

Regression analyses identified one significant moderation model: average blood oxygen saturation (AVO2) and depression predicting recall memory, accounting for 31% of the performance variance, p<.001. Depression was a significant predictor of recall memory, p<.001, but AVO2 was not a significant predictor. The interaction between depression and AVO2 was significant, accounting for an additional 10% of the variance, p<.001. The relationship between low AVO2 and low recall memory performance emerged when depression severity ratings approached a previously established clinical cutoff score (CESD=16).

CONCLUSIONS

This study examined sleep biomarkers with specific neurocognitive functions among individuals with suspected OSA. Findings revealed that depression burden uniquely influence this pathophysiological relationship, which may aid clinical management. (JINS, 2018, 28, 864-875).

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. This is where the consensus ends. Despite a number of competing explanations regarding how OSA affects cognition, reliable evidence is hard to find, which may relate to the many, common conditions co-morbid with OSA or to the methodological challenges in this field. This paper reviews the evidence for cognitive impairment in OSA, the proposed models of cognitive harm, the impact of co-morbidities and the many methodological and theoretical challenges of exploring the effect of OSA on cognition. To overcome some of these challenges, we end by proposing a number of future directions for the field, including suggesting some core design elements for future studies.

Interaction of obstructive sleep apnoea and cognitive impairment with slow gait speed in middle-aged and older adults

Objective

to investigate whether slow gait speed is associated with cognitive impairment and further whether the association is modified by obstructive sleep apnoea (OSA).

Methods

in total, 2,222 adults aged 49-80 years, free from dementia, stroke and head injury were asked to walk a 4-m course at fast and usual gait speeds. The time taken to walk was measured. All participants completed the Korean Mini-Mental State Examination, which was validated in the Korean language, to assess cognitive function. Additionally, the participants completed a polysomnography test to ascertain OSA (defined as an apnoea-hypopnoea index ≥15). Multivariable linear regression models were utilised to test the associations.

Results

time taken to walk 4 m showed significant inverse associations with cognitive scores (P value = 0.001 at fast gait speed and P = 0.002 at usual gait speed). Furthermore, a significant interaction according to OSA on the association between time to walk and cognitive impairment was found (P value for interaction = 0.003 at fast gait speed and P value for interaction = 0.007 at usual gait speed).

Conclusion

we found that the inverse association between the time taken to walk 4 m and a cognitive score became significantly stronger, if an individual had OSA.

Co-Morbidity, Mortality, Quality of Life and the Healthcare/Welfare/Social Costs of Disordered Sleep: A Rapid Review

Sleep disorders are frequent (18%-23%) and constitute a major risk factor for psychiatric, cardiovascular, metabolic or hormonal co-morbidity and mortality. Low social status or income, unemployment, life events such as divorce, negative lifestyle habits, and professional requirements (e.g., shift work) are often associated with sleep problems. Sleep disorders affect the quality of life and impair both professional and non-professional activities. Excessive daytime drowsiness resulting from sleep disorders impairs efficiency and safety at work or on the road, and increases the risk of accidents. Poor sleep (either professional or voluntary) has detrimental effects comparable to those of major sleep disorders, but is often neglected. The high incidence and direct/indirect healthcare and welfare costs of sleep disorders and poor sleep currently constitute a major medical problem. Investigation, monitoring and strategies are needed in order to prevent/reduce the effects of these disorders.

Impact of Obstructive Sleep Apnea on Neurocognitive Function and Impact of Continuous Positive Air Pressure

There is evidence that obstructive sleep apnea (OSA) can negatively impact attention, memory, learning, executive function, and overall intellectual function in adults and children. Imaging techniques, including MRI, MR diffusion tensor imaging, MR spectroscopy, and fMRI, have provided additional insight into the anatomic and functional underpinnings of OSA-related cognitive impairment. Both animal and human studies have looked to elucidate the separate effects of oxygen desaturation and sleep fragmentation on independent aspects of cognition. Data from animal models point to neuro-inflammation and oxidative stress as driving factors of cognitive impairment.

The Cognitive Effects of Obstructive Sleep Apnea: An Updated Meta-analysis

This meta-analysis set out to ascertain the cognitive function of obstructive sleep apnea (OSA) patients as measured through objective neuropsychological tests. The meta-analysis investigated the cognitive functioning of these patients prior to them receiving any treatment such as continuous positive airway pressure (CPAP). A total of 19 studies met the study inclusion criteria. Results revealed statistically significant negative effect sizes in the cognitive domains of non-verbal memory, concept formation, psychomotor speed, construction, executive functioning, perception, motor control and performance, attention, speed of processing, working and verbal memory, verbal functioning and verbal reasoning. The clinical implication of these results, the possible causal mechanisms of the cognitive impairments and the implication of these for future research were each discussed. Despite a number of important limitations, the analysis highlights the need for clinicians to comprehensively explore complaints about sleep disturbance, particularly OSA, in all clinical assessments to ensure control for this important confounder in order to ensure appropriate attribution of the source of any observed cognitive compromise.

Cognitive impairment in obstructive sleep apnea

Obstructive sleep apnea (OSA) is characterised by repetitive cessation or reduction of airflow due to upper airway obstructions. These respiratory events lead to chronic sleep fragmentation and intermittent hypoxemia. Several studies have shown that OSA is associated with daytime sleepiness and cognitive dysfunctions, characterized by impairments of attention, episodic memory, working memory, and executive functions. This paper reviews the cognitive profile of adults with OSA and discusses the relative role of altered sleep and hypoxemia in the aetiology of these cognitive deficits. Markers of cognitive dysfunctions such as those measured with waking electroencephalography and neuroimaging are also presented. The effects of continuous positive airway pressure (CPAP) on cognitive functioning and the possibility of permanent brain damage associated with OSA are also discussed. Finally, this paper reviews the evidence suggesting that OSA is a risk factor for developing mild cognitive impairment and dementia in the aging population and stresses the importance of its early diagnosis and treatment.