Neuropsychological investigations and event-related potentials in obstructive sleep apnea syndrome before and during CPAP-therapy

Brainstem impairment in obstructive sleep apnoea and the effect of CPAP treatment: an electrophysiological blink reflex study

PURPOSE

This study aimed to evaluate the functionality of the brainstem structures through the blink reflex (BR) test in patients with obstructive sleep apnoea (OSA) and to assess the effects of continuous positive airway pressure (CPAP) treatment on BR responses.

METHODS

Patients with moderate-severe OSA and controls underwent BR testing. Patients with OSA who were adherent to CPAP therapy repeated BR testing at 6 months follow-up. CPAP adherence was defined as CPAP use for ≥ 4 hour per night on > 5 nights per week with residual apnoea-hypopnea index less than 5 events per hour.

RESULTS

A total of 22 patients with OSA (86% male, mean age 57.8 ± 10.6 years) and 20 controls (60% male, mean age 55.3 ± 9.3 years) were included. Patients with OSA showed longer right and left R1 latency, as well as delayed right ipsilateral and contralateral R2 latencies compared to controls. Patients with OSA who were compliant with CPAP treatment (n = 16; 88% men, mean age 58.8 ± 9.7 years) showed a significant decrease in latency of the right ipsilateral and contralateral R2 responses at 6 months.

CONCLUSION

This study showed an abnormal pattern of BR responses in patients with OSA, consistent with a significant impairment of brainstem functionality in OSA. CPAP treatment partially improved the BR responses, suggesting the importance of treating OSA.

Clinical features of sleep apnea syndrome and cognitive impairment in multiple sclerosis

BACKGROUND

Complications of obstructive sleep apnea (OSA) have been reported in patients with multiple sclerosis (MS). Patients with sleep apnea syndrome (SAS) due to OSA also show cognitive decline, with similar clinical characteristics to that manifested in MS. SAS due to OSA is a treatable condition, and the associated cognitive decline is expected to improve. This study investigates clinical features of SAS in people living with MS and contribute to improve cognitive dysfunction of MS.

METHODS

A case-control study was conducted. Cognitive functions were evaluated by the Symbol Digit Modalities Test (SDMT) and the Paced Auditory Serial Addition Test 2 (PASAT-2) and 3 (PASAT-3). The Respiratory Event Index (REI) was measured using Out of Center Sleep Testing (OCST). We defined subjects with REI ≥ 5 as OSA and divided participants into two groups with or without SAS due to OSA. Cognitive and respiratory characteristics were statistically compared between patients with MS and healthy controls.

RESULTS

We enrolled 67 people living with MS and 31 age- and sex-matched controls. OCST detected OSA in people living with MS and controls, and the prevalence rates were 28.4 % and 25.8 %, respectively. REI values (5.2 ± 7.9 vs 3.9 ± 5.2, p = 0.509) and number of participants with REI ≥ 5 (19 vs 8, p = 0.793) were similar between the MS and control group. The SDMT, PASAT-2, and PASAT-3 scores were significantly lower in the MS group than the control group (p < 0.001, p = 0.001, and p < 0.001, respectively). The interaction effect of MS and SAS on cognitive function was not significant in the SDMT (p = 0.078), but in the PASAT-2 (p = 0.043) and PASAT-3 (p = 0.020).

CONCLUSION

This study revealed the prevalence rates of SAS in Japanese people living with MS and the usefulness of OCST for detection of SAS. This study also revealed that concomitant SAS can facilitate cognitive decline in people living with MS. These findings suggest that an appropriate intervention for OSA can be beneficial for people living with MS with cognitive decline.

The role of ferroptosis in chronic intermittent hypoxia-induced cognitive impairment

PURPOSE

Obstructive sleep apnea (OSA) is a sleep disorder that may lead to cognitive impairment. The primary pathophysiological feature of OSA is chronic intermittent hypoxia (CIH), but the underlying mechanisms of CIH are not known. There have been few studies on the role of ferroptosis, a novel form of programmed cell death, during CIH-induced cognitive impairment. Therefore, this paper examined ferroptosis' effect on CIH-mediated cognitive impairment.

METHODS

The study randomized twenty-four Sprague-Dawley (SD) male rats to control or CIH group. CIH rats were subjected to intermittent hypoxia for 4 weeks. Rat learning and memory were analyzed by the Morris water maze (MWM) test. Alterations of hippocampal neuronal ultrastructure were observed by transmission electron microscopy (TEM). Malondialdehyde (MDA) and ferrous iron (Fe2+) levels and superoxide dismutase (SOD) and reduced glutathione (GSH) contents were determined. Ferroptosis-associated protein levels were examined by Western blotting.

RESULTS

The MWM test indicated that rats in the CIH group exhibited neurocognitive impairment. TEM showed that CIH induced mitochondrial damage. Significant increases in Fe2+ and MDA levels were observed in the CIH group, and GSH and SOD levels were decreased. Expression of Acyl-CoA synthetase long-chain family member 4 (ACSL4) increased, and glutathione peroxidase 4 (GPX4) protein levels were decreased, suggesting that ferroptosis was induced in CIH model rats. The NF-E2-related factor 2 (Nrf2) protein level in the CIH group was decreased.

CONCLUSION

Ferroptosis had an essential effect on CIH-mediated cognitive impairment, and it may occur via Nrf2 dysregulation. These findings lay a solid foundation for the subsequent study of OSA-associated cognitive impairment offering potential evidence for the development of therapeutic strategies.

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.

Short-Term Benefits of Continuous Positive Airway Pressure Treatment on Cognition in the Obstructive Sleep Apnea Syndrome: A Retrospective Study

The Obstructive Sleep Apnea Syndrome (OSAS) significantly impacts cognitive functioning. The prolonged use (more than 3 months) of ventilotherapy with continuous positive airway pressure (CPAP) seems to have positive effects in restoring cognitive difficulties. However, there is poor evidence about its possible short-term effect. We investigated whether the short use (less than 15 days at testing) of CPAP improved the cognitive functioning in fifty individuals with OSAS by collecting retrospective neuropsychological measures about verbal memory and learning, information processing speed, attention (i.e., alerting, orienting, and executive system), and executive functions (i.e., strategic reasoning, problem-solving, and mental planning). The predictive role of days of CPAP use on the neuropsychological scores was assessed by hierarchical multiple linear regression analyses, over and above the possible role of demographics, body mass index, level of OSAS severity, and the level of anxiety and depression. The average number of days since CPAP adaptation was 4.70 (SD = 3.90; range = 0-15). As the days of CPAP adaptation increased, verbal learning and long-term memory significantly improved, contrary to the other assessed domains. Our results show a significant improvement in some cognitive functions even after a short treatment with CPAP, pointing to the importance of the early use of ventilotherapy to rapidly improve cognitive functioning. Identifying which cognitive functions can or cannot be restored with CPAP use may enable the design of complementary neuropsychological interventions focused on those residual difficulties, possibly enhancing patients' compliance to the treatment.

Respiratory-related evoked potentials in chronic obstructive pulmonary disease and healthy aging

Altered neural processing and increased respiratory sensations have been reported in chronic obstructive pulmonary disease (COPD) as larger respiratory-related evoked potentials (RREPs), but the effect of healthy-aging has not been considered adequately. We tested RREPs evoked by brief airway occlusions in 10 participants with moderate-to-severe COPD, 11 age-matched controls (AMC) and 14 young controls (YC), with similar airway occlusion pressure stimuli across groups. Mean age was 76 years for COPD and AMC groups, and 30 years for the YC group. Occlusion intensity and unpleasantness was rated using the modified Borg scale, and anxiety rated using the Hospital Anxiety and Depression Scale. There was no difference in RREP peak amplitudes across groups, except for the N1 peak, which was significantly greater in the YC group than the COPD and AMC groups (p = 0.011). The latencies of P1, P2 and P3 occurred later in COPD versus YC (p < 0.05). P3 latency occurred later in AMC than YC (p = 0.024). COPD and AMC groups had similar Borg ratings for occlusion intensity (3.0 (0.5, 3.5) [Median (IQR)] and 3.0 (3.0, 3.0), respectively; p = 0.476) and occlusion unpleasantness (1.3 (0.1, 3.4) and 1.0 (0.75, 2.0), respectively; p = 0.702). The COPD group had a higher anxiety score than AMC group (p = 0.013). A higher N1 amplitude suggests the YC group had higher cognitive processing of respiratory inputs than the COPD and AMC groups. Both COPD and AMC groups showed delayed neural responses to the airway occlusion, which may indicate impaired processing of respiratory sensory inputs in COPD and healthy aging.

Therapeutic Strategies for Mitigating Driving Risk in Patients with Narcolepsy

Narcolepsy is a central nervous system hypersomnia disorder characterized by uncontrollable episodes of daytime sleep, sleep state instability, and cataplexy (sudden loss of muscle tone precipitated by emotion). Individuals with narcolepsy report more frequent sleep-related crashes, near crashes, and drowsy driving than drivers with other sleep disorders. As such, evaluating risk of sleep-related crashes is of great importance for this patient population. There are no established guidelines for ensuring driving safety in patients with narcolepsy; however, many providers currently use a combination of subjective report, report of prior crashes or near-misses, report of previously falling asleep while driving, sleepiness screening tools, and maintenance of wakefulness testing (MWT) to determine risk. Driving simulator tests, though often unavailable to the clinician, provide data to support the use of MWT for evaluation of alertness in drivers with narcolepsy. Treatments such as modafinil may improve driving performance; however, the impact of other treatments such as stimulants and sodium oxybate on driving has not been extensively studied. Behavioral and lifestyle modifications may also reduce risk, including scheduled naps, driving only short distances, and avoiding driving after meals, sedating medications, and alcohol intake. Even with effective treatment, alertness in patients with narcolepsy may never reach that of normal drivers; however, studies have suggested that narcolepsy patients may be able to drive safely with appropriate limitations.

Cognitive impairment in obstructive sleep apnea syndrome: a descriptive review

PURPOSE

Obstructive sleep apnea syndrome is a clinical sleep disorder defined by total or partial airflow restraint during sleep that results in fragmented sleep and hypoxemia, impacting negatively with cognitive functioning. This review was conducted on studies investigating structural brain alteration and cognitive impairment in obstructive sleep apnea syndrome.

METHOD

We searched on PubMed databases and screening references of included studies and review articles for additional citations. From initial 190 publications, only 17 met search criteria and described the cognitive impairment in obstructive sleep apnea syndrome.

RESULTS

Findings showed that patients with this syndrome had worse performance than healthy controls in attention, memory, and executive functions, showing specific neuroanathomical features. Cognitive impairment is also related to the severity of pathology. Treatment could improve certain cognitive aspects.

CONCLUSIONS

Cognitive deficits seem to be mainly attributable to decreased daytime vigilance and nocturnal hypoxemia.

Slow-wave activity surrounding stage N2 K-complexes and daytime function measured by psychomotor vigilance test in obstructive sleep apnea

STUDY OBJECTIVE

To better understand the inter-individual differences in neurobehavioral impairment in obstructive sleep apnea (OSA) and its treatment with continuous positive airway pressure (CPAP), we examined how changes in sleep electroencephalography (EEG) slow waves were associated with next-day psychomotor vigilance test (PVT) performance.

METHODS

Data from 28 OSA subjects (Apnea-Hypopnea Index with 3% desaturation and/or with an associated arousal [AHI3A] > 15/hour; AHI3A = sum of all apneas and hypopneas with 3% O2 desaturation and/or an EEG arousal, divided by total sleep time [TST]), who underwent three full in-lab nocturnal polysomnographies (NPSGs: chronic OSA, CPAP-treated OSA, and acute OSA), and 19 healthy sleepers were assessed. Four 20-minute PVTs were performed after each NPSG along with subjective and objective assessment of sleepiness. Three EEG metrics were calculated: K-complex (KC) Density (#/minute of N2 sleep), change in slow-wave activity in 1-second envelopes surrounding KCs (ΔSWAK), and relative frontal slow-wave activity during non-rapid eye movement (NREM) (%SWA).

RESULTS

CPAP treatment of OSA resulted in a decrease in KC Density (chronic: 3.9 ± 2.2 vs. treated: 2.7 ± 1.1; p < 0.01; mean ± SD) and an increase in ΔSWAK (chronic: 2.6 ± 2.3 vs. treated: 4.1 ± 2.4; p < 0.01) and %SWA (chronic: 20.9 ± 8.8 vs. treated: 26.6 ± 8.6; p < 0.001). Cross-sectionally, lower ΔSWAK values were associated with higher PVT Lapses (chronic: rho = -0.55, p < 0.01; acute: rho = -0.46, p = 0.03). Longitudinally, improvement in PVT Lapses with CPAP was associated with an increase in ΔSWAK (chronic to treated: rho = -0.48, p = 0.02; acute to treated: rho = -0.5, p = 0.03). In contrast, OSA severity or global sleep quality metrics such as arousal index, NREM, REM, or TST were inconsistently associated with PVT Lapses.

CONCLUSION

Changes in EEG slow waves, in particular ∆SWAK, explain inter-individual differences in PVT performance better than conventional NPSG metrics, suggesting that ΔSWAK is a night-time correlate of next-day vigilance in OSA.

Therapeutic effects of CPAP on cognitive impairments associated with OSA

Obstructive sleep apnea (OSA) is the most common type of sleep apnea and caused by upper airway obstructions. Clinically, patients with OSA characteristically experience intermittent nocturnal hypoxemia and impaired sleep quality. Cognitive impairments are commonly seen in patients with an OSA diagnosis. A literature search on OSA, cognitive impairments and CPAP was performed with various electronic databases including Medline, EMBASE and Google Scholar. The chosen evidence was limited to human subject studies only, and reports on either central sleep apnea or non-classified sleep apnea were excluded. Available evidence has been systemically reviewed to ascertain what types of cognitive impairments are related to OSA as well as the pathological connections. In addition, effectiveness of continuous positive airway pressure (CPAP) was analyzed as a standard therapy for improving cognitive performance in patients with OSA. The review contributed in: (1) delineating OSA as a risk factor of cognitive impairments; (2) enumerating cognitive impairments seen in patients with OSA; (3) substantiating the relation between OSA and cognitive impairments from the pathological perspective of AD biomarkers; and (4) revealing duration of CPAP is crucial for its therapeutic effects on improving cognitive performance in patients with OSA.

Electrophysiological and neuropsychological outcomes of severe obstructive sleep apnea: effects of hypoxemia on cognitive performance

Obstructive sleep apnea syndrome (OSAS) is a sleep disorder characterized with upper airway obstructions. Some studies showed cognitive and electrophysiological changes in patients with OSAS; however, contradictory results were also reported. The purpose of the present study was twofold: (1) to investigate cognitive changes in severe OSAS patients by using neuropsychological tests and electrophysiological methods together, (2) to investigate influence of hypoxemia levels on cognition. Fifty-four severe OSAS patients and 34 age-, gender- and education matched healthy subjects were participated. OSAS patients were further divided into two subgroups according to minimum oxygen saturation levels. All participants underwent a detailed neuropsychological test battery. A classical visual oddball task was used to elicit ERP P300 and mean P300 amplitudes were measured from F_z, C_z and P_z electrode sites. OSAS patients showed reduced mean P300 amplitudes up to 43-51% on all electrode sites compared to healthy controls. Subgroup analysis revealed significant differences in neuropsychological test scores between healthy controls and high hypoxemia OSAS group, as well as between low and high hypoxemia groups. Moreover, both low and high hypoxemia OSAS groups had lower P300 amplitudes compared with healthy controls. P300 amplitudes showed a gradual decline in parallel with increasing hypoxemia severity; however, the difference between high and low hypoxemia OSAS groups did not reach significance. Moderate correlations were found between sleep parameters, neuropsychological test scores and P300 amplitudes. These results suggest that electrophysiological measures could be better indicators of cognitive changes than neuropsychological tests in OSAS, particularly in mildly affected patients.

Treatment of intermittent hypoxia increases phosphorylated tau in the hippocampus via biological processes common to aging

Sleep-disordered breathing produces cognitive impairments, and is possibly associated with Alzheimer disease (AD). Intermittent hypoxia treatment (IHT), an experimental model for sleep-disordered breathing, results in cognitive impairments in animals via unknown mechanisms. Here, we exposed mice to IHT protocols, and performed biochemical analyses and microarray analyses regarding their hippocampal samples. In particular, we performed gene ontology (GO)-based microarray analysis to elucidate effects of IHT on hippocampal functioning, which were compared with the effects of various previously-reported experimental conditions on that (ref. Gene Expression Omnibus, The National Center for Biotechnology Information). Our microarray analyses revealed that IHT and aging shared alterations in some common GO, which were also observed with kainic acid treatment, Dicer ablation, or moderate glutamate excess. Mapping the altered genes using the Kyoto Encyclopedia of Genes and Genomes PATHWAY database indicated that IHT and aging affected several pathways including “MAPK signaling pathway”, “PI3K-Akt signaling pathway”, and “glutamatergic synapse”. Consistent with the gene analyses, in vivo analyses revealed that IHT increased phosphorylated tau, reflecting an imbalance of kinases and/or phosphatases, and reduced proteins relevant to glutamatergic synapses. In addition, IHT increased phosphorylated p70 S6 kinase, indicating involvement of the mammalian target of rapamycin signaling pathway. Furthermore, IHT mice demonstrated hyperactivity in Y-maze tests, which was also observed in AD models. We obtained important data or something from the massive amount of microarray data, and confirmed the validity by in vivo analyses: the IHT-induced cognitive impairment may be partially explained by the fact that IHT increases phosphorylated tau via biological processes common to aging. Moreover, as aging is a major risk factor for AD, IHT is a novel model for investigating the pathological processes contributing to AD onset.

Obstructive sleep apnea and its controversial effects on cognition

Obstructive sleep apnea syndrome is a sleep disorder that may affect many brain functions. We are interested in the cognitive consequences of the condition with regard to the quality of life of individuals with this disorder. A debate is still underway as to whether cognitive difficulties caused by obstructive sleep apnea actually induce a "pseudodementia" pattern. This work provides a brief overview of the main controversies currently surrounding this issue. We report findings and opinions on structural and cognitive brain changes in individuals affected by obstructive sleep apnea by highlighting the involvement of executive functions and the possible reversibility of signs following-treatment with continuous positive airway pressure. Much research has been done on this issue but, to the best of our knowledge, a review of the present state of the literature evaluating different points of view has not yet been carried out.

Sleep and Cognitive Function in Multiple Sclerosis

STUDY OBJECTIVES

To examine associations between cognitive performance and polysomnographic measures of obstructive sleep apnea in patients with multiple sclerosis (MS).

METHODS

Participants underwent a comprehensive MS-specific cognitive testing battery (the Minimal Assessment of Cognitive Function in MS, or MACFIMS) and in-laboratory overnight PSG.

RESULTS

In adjusted linear regression models, the oxygen desaturation index (ODI) and minimum oxygen saturation (MinO2) were significantly associated with performance on multiple MACFIMS measures, including the Paced Auditory Serial Addition Test (PASAT; 2-sec and 3-sec versions), which assesses working memory, processing speed, and attention, and on the Brief Visuospatial Memory Test-Revised, a test of delayed visual memory. The respiratory disturbance index (RDI) was also significantly associated with PASAT-3 scores as well as the California Verbal Learning Test-II (CVLT-II) Discriminability Index, a test of verbal memory and response inhibition. Among these associations, apnea severity measures accounted for between 12% and 23% of the variance in cognitive test performance. Polysomnographic measures of sleep fragmentation (as reflected by the total arousal index) and total sleep time also showed significant associations with a component of the CVLT-II that assesses response inhibition, explaining 18% and 27% of the variance in performance.

CONCLUSIONS

Among patients with MS, obstructive sleep apnea and sleep disturbance are significantly associated with diminished visual memory, verbal memory, executive function (as reflected by response inhibition), attention, processing speed, and working memory. If sleep disorders degrade these cognitive functions, effective treatment could offer new opportunities to improve cognitive functioning in patients with MS.

COMMENTARY

A commentary on this article appears in this issue on page 1489.

Overnight Motor Skill Learning Outcomes in Obstructive Sleep Apnea: Effect of Continuous Positive Airway Pressure

STUDY OBJECTIVE

To determine the effectiveness of continuous positive airway pressure (CPAP) therapy in alleviating known impairments in the overnight consolidation of motor skill learning in patients with obstructive sleep apnea (OSA).

METHODS

Twenty-five patients with untreated moderate-severe OSA, 13 first-night CPAP users, 17 compliant CPAP users, and 14 healthy control patients were trained on a motor sequence learning task (Sequential Finger Tapping Task, SFTT) and were subsequently tested prior to and after polysomnographic recorded sleep. Measures of subjective sleepiness (Karolinska Sleepiness Scale) and sustained attention (Psychomotor Vigilance Task) were also completed before and after sleep.

RESULTS

Typical analyses of overnight improvement on the SFTT show significantly greater overnight gains in motor task speed in controls (+11.6 ± 4.7%, p = 0.007) and compliant CPAP users (+8.9 ± 4.3%, p = 0.008) compared to patients with OSA (-4.86 ± 4.5%). Additional analyses suggest that these improvements in motor performance occurred prior to the sleep episode, as all groups significantly improved (15% to 22%) over a 10-min presleep rest period. Thereafter, performance in all groups significantly deteriorated over sleep (6% to 16%) with trends toward patients with OSA showing greater losses in performance compared to control patients and compliant CPAP users. No between-group differences in subjective sleepiness and sustained attention were found presleep and postsleep.

CONCLUSIONS

The current data suggest impairments in overnight motor learning in patients with OSA may be a combination of deficient stabilization of memory over a sleep episode as well as increased vulnerability to time on task fatigue effects. Compliant CPAP usage possibly offsets both of these impediments to learning outcomes by improving both sleep quality and subsequent daytime function.

A review of neurocognitive function and obstructive sleep apnea with or without daytime sleepiness

Excessive daytime sleepiness (EDS) and neurocognitive dysfunction are commonly observed in patients with obstructive sleep apnea (OSA), and these daytime functional deficits can be reversed partly or completely with treatment such as continuous positive airway pressure (CPAP). Although daytime sleepiness is a possible etiology for neurocognitive dysfunction in OSA patients, EDS is not universally present in all patients with OSA. The objective of this review is to summarize the relationship between neurocognitive function and EDS in OSA, as well as the difference in cognitive domains, improvement, and application of CPAP therapy between patients with and without EDS. Two authors independently searched PubMED/Medline, The Cochrane Library and Scopus through May 27, 2015. Sixty-five articles were included in this review. The literature demonstrated a wide range of neurocognitive deficits in OSA patients with EDS, but no more extensive and complex cognitive domains (eg, executive function) in patients without EDS. However, the current literature had very few studies with large sample sizes and extended follow-up that evaluated the effect of CPAP for OSA in patients with and without sleepiness. CPAP failed to improve cognitive dysfunction in OSA patients without EDS after short-term therapy. The evidence suggests that daytime sleepiness possibly relates to the domain and extent of cognitive impairments in OSA, and CPAP therapy has little effect on the improvement of cognitive deficits in OSA patients without EDS. We recommend that additional prospective studies be performed to further quantify the relationship between neurocognitive function in OSA patients with and without EDS.

Obstructive Sleep Apnea and Cognition in Parkinson's disease

OBJECTIVE

Obstructive sleep apnea (OSA) is very common in Parkinson's disease (PD). OSA is known to affect patients' cognition. The present study assessed whether PD patients with OSA (PD + OSA) score lower on cognitive measures than those without OSA (PD - OSA). In addition, this study evaluated whether treating the OSA with continuous positive airway pressure (CPAP) in PD + OSA patients results in an improved cognitive functioning.

METHODS

Eighty-six patients with PD underwent an overnight polysomnography screen for OSA and were administered the Mini-Mental Status Exam (MMSE) and the Montreal Cognitive Assessment (MoCA). This resulted in 38 patients with PD + OSA who were randomly assigned to receive either therapeutic CPAP for 6 weeks (n = 19) or placebo CPAP for three weeks followed by therapeutic CPAP for three weeks (n = 19). Intervention participants completed a neurocognitive battery at baseline and 3- and 6-week time-points.

RESULTS

Patients with PD + OSA scored significantly lower than PD - OSA on the MMSE and MoCA after controlling for age, education, and PD severity. OSA was a significant predictor of cognition (MMSE p <0.01; MoCA p = 0.028).There were no significant changes between groups in cognition when comparing three weeks of therapeutic CPAP with 3 weeks of placebo CPAP. Comparisons between pre-treatment and 3-week post-therapeutic CPAP for the entire sample also revealed no significant changes on overall neuropsychological (NP) scores.

CONCLUSIONS

Findings suggest that PD patients with OSA show worse cognitive functioning on cognitive screening measures than those without OSA. However, OSA treatment after three or six weeks of CPAP may not result in overall cognitive improvement in patients with PD.

Interactions between the perception of age and ethnicity in faces: an event-related potential study

Face perception models propose that different facial attributes are processed by anatomically distinct neural pathways that partially overlap. Whether these attributes interact functionally is an open question. Our goal was to determine if there are interactions between age and ethnicity processing and, if so, at what temporal epoch these interactions are evident. We monitored event-related potentials on electroencephalography while subjects categorized faces by age or ethnicity in two conditions: a baseline in which the other of these two properties not being categorized was held constant and an interference condition in which it also varied, as modelled after the Garner interference paradigm. We found that, when participants were categorizing faces by age, variations in ethnicity increased the amplitude of the right face-selective N170 component. When subjects were categorizing faces by ethnicity, variations in age did not alter the N170. We concluded that there is an asymmetric pattern of influence between age and ethnicity on early face-specific stages of visual processing, which has parallels with behavioural evidence of asymmetric interactions between identity and expression processing of faces.

Sleep deprivation impairs inhibitory control during wakefulness in adult sleepwalkers

Sleepwalkers often complain of excessive daytime somnolence. Although excessive daytime somnolence has been associated with cognitive impairment in several sleep disorders, very few data exist concerning sleepwalking. This study aimed to investigate daytime cognitive functioning in adults diagnosed with idiopathic sleepwalking. Fifteen sleepwalkers and 15 matched controls were administered the Continuous Performance Test and Stroop Colour-Word Test in the morning after an overnight polysomnographic assessment. Participants were tested a week later on the same neuropsychological battery, but after 25 h of sleep deprivation, a procedure known to precipitate sleepwalking episodes during subsequent recovery sleep. There were no significant differences between sleepwalkers and controls on any of the cognitive tests administered under normal waking conditions. Testing following sleep deprivation revealed significant impairment in sleepwalkers' executive functions related to inhibitory control, as they made more errors than controls on the Stroop Colour-Word Test and more commission errors on the Continuous Performance Test. Sleepwalkers' scores on measures of executive functions were not associated with self-reported sleepiness or indices of sleep fragmentation from baseline polysomnographic recordings. The results support the idea that sleepwalking involves daytime consequences and suggest that these may also include cognitive impairments in the form of disrupted inhibitory control following sleep deprivation. These disruptions may represent a daytime expression of sleepwalking's pathophysiological mechanisms.

First night of CPAP: impact on memory consolidation attention and subjective experience

OBJECTIVE

Neurocognitive deficits are common and serious consequences of obstructive sleep apnea (OSA). Currently, the gold standard treatment is continuous positive air pressure (CPAP) therapy, although the clinical responses to this intervention can be variable. This study examined the effect of one night of CPAP therapy on sleep-dependent memory consolidation, attention, and vigilance as well as subjective experience.

METHODS

Fifteen healthy controls and 29 patients with obstructive sleep apnea of whom 14 underwent a full-night CPAP titration completed the psychomotor vigilance test (PVT) and motor sequence learning task (MST) in the evening and the morning after undergoing overnight polysomnography. All participants also completed subjective evaluations of sleep quality.

RESULTS

Participants with OSA showed significantly less overnight improvement on the MST compared to controls without OSA, independent of whether or not they had received CPAP treatment, while there was no significant difference between the untreated OSA and CPAP-treated patients. Within the OSA group, only those receiving CPAP exhibited faster reaction times on the PVT in the morning. Compared to untreated OSA patients, they also felt subjectively more rested and reported that they slept better.

CONCLUSION

Our results demonstrate an instant augmentation of subjective experience and, based on PVT results, attention and vigilance after one night of CPAP, but a lack of an effect on offline sleep-dependent motor memory consolidation. This dissociation may be explained by different brain structures underlying these processes, some of which might require longer continued adherence to CPAP to generate an effect.

Detection of cognitive impairment in patients with obstructive sleep apnea hypopnea syndrome using mismatch negativity

In this experiment, 97 patients with obstructive sleep apnea hypopnea syndrome were divided into three groups (mild, moderate, severe) according to minimum oxygen saturation, and 35 healthy subjects were examined as controls. Cognitive function was determined using the mismatch negativity paradigm and the Montreal Cognitive Assessment. The results revealed that as the disease worsened, the mismatch negativity latency was gradually extended, and the amplitude gradually declined in patients with obstructive sleep apnea hypopnea syndrome. Importantly, mismatch negativity latency in severe patients with a persistent time of minimum oxygen saturation < 60 seconds was significantly shorter than that with a persistent time of minimum oxygen saturation > 60 seconds. Correlation analysis revealed a negative correlation between minimum oxygen saturation latency and Montreal Cognitive Assessment scores. These findings indicate that intermittent night-time hypoxemia affects mismatch negativity waveforms and Montreal Cognitive Assessment scores. As indicators for detecting the cognitive functional status of obstructive sleep apnea hypopnea syndrome patients, the sensitivity of mismatch negativity is 82.93%, the specificity is 73.33%, the accuracy rate is 81.52%, the positive predictive value is 85.00%, the negative predictive value is 70.21%, the positive likelihood ratio is 3, and the negative likelihood ratio is 0.23. These results indicate that mismatch negativity can be used as an effective tool for diagnosis of cognitive dysfunction in obstructive sleep apnea hypopnea syndrome patients.

Sleep in older adults: normative changes, sleep disorders, and treatment options

Approximately 5% of older adults meet criteria for clinically significant insomnia disorders and 20% for sleep apnea syndromes. It is important to distinguish age-appropriate changes in sleep from clinically significant insomnia, with the latter having associated daytime impairments. Non-pharmacologic therapies, such as cognitive-behavioral therapy for insomnia, can be highly effective with sustained benefit. Pharmacologic therapies are also available, but may be associated with psychomotor effects. A high index of suspicion is crucial for effective diagnosis of sleep apnea because symptoms commonly noted in younger patients, such as obesity or loud snoring, may not be present in older patients.

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.

Effects of chronic obstructive pulmonary disease and obstructive sleep apnea on cognitive functions: evidence for a common nature

Patients with chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea syndrome (OSAS) show similar neurocognitive impairments. Effects are more apparent in severe cases, whereas in moderate and mild cases the effects are equivocal. The exact mechanism that causes cognitive dysfunctions in both diseases is still unknown and only suggestions have been made for each disease separately. The primary objective of this review is to present COPD and OSAS impact on cognitive functions. Secondly, it aims to examine the potential mechanisms by which COPD and OSAS can be linked and provide evidence for a common nature that affects cognitive functions in both diseases. Patients with COPD and OSAS compared to normal distribution show significant deficits in the cognitive abilities of attention, psychomotor speed, memory and learning, visuospatial and constructional abilities, executive skills, and language. The severity of these deficits in OSAS seems to correlate with the physiological events such as sleep defragmentation, apnea/hypopnea index, and hypoxemia, whereas cognitive impairments in COPD are associated with hypoventilation, hypoxemia, and hypercapnia. These factors as well as vascocerebral diseases and changes in systemic hemodynamic seem to act in an intermingling and synergistic way on the cause of cognitive dysfunctions in both diseases. However, low blood oxygen pressure seems to be the dominant factor that contributes to the presence of cognitive deficits in both COPD and OSAS.

Death by a thousand cuts in Alzheimer's disease: hypoxia--the prodrome

A wide range of clinical consequences may be associated with obstructive sleep apnea (OSA) including systemic hypertension, cardiovascular disease, pulmonary hypertension, congestive heart failure, cerebrovascular disease, glucose intolerance, impotence, gastroesophageal reflux, and obesity, to name a few. Despite this, 82 % of men and 93 % of women with OSA remain undiagnosed. OSA affects many body systems, and induces major alterations in metabolic, autonomic, and cerebral functions. Typically, OSA is characterized by recurrent chronic intermittent hypoxia (CIH), hypercapnia, hypoventilation, sleep fragmentation, peripheral and central inflammation, cerebral hypoperfusion, and cerebral glucose hypometabolism. Upregulation of oxidative stress in OSA plays an important pathogenic role in the milieu of hypoxia-induced cerebral and cardiovascular dysfunctions. Strong evidence underscores that cerebral amyloidogenesis and tau phosphorylation--two cardinal features of Alzheimer's disease (AD), are triggered by hypoxia. Mice subjected to hypoxic conditions unambiguously demonstrated upregulation in cerebral amyloid plaque formation and tau phosphorylation, as well as memory deficit. Hypoxia triggers neuronal degeneration and axonal dysfunction in both cortex and brainstem. Consequently, neurocognitive impairment in apneic/hypoxic patients is attributable to a complex interplay between CIH and stimulation of several pathological trajectories. The framework presented here helps delineate the emergence and progression of cognitive decline, and may yield insight into AD neuropathogenesis. The global impact of CIH should provide a strong rationale for treating OSA and snoring clinically, in order to ameliorate neurocognitive impairment in aged/AD patients.

Neurocognitive functioning in children with obstructive sleep apnea syndrome: a pilot study of positive airway pressure therapy

Studies of individuals with obstructive sleep apnea syndrome (OSAS) have shown impairment in neurocognitive function. This study investigated the neurocognitive function in children with OSAS before and after positive airway pressure (PAP) therapy. Twenty-one participants with suspected/documented OSAS were recruited, completing the Epworth Sleepiness Scale (ESS), the Child Sleep Habit Questionnaire (CSHQ), and/or the Pittsburgh Sleep Quality Index. Participants were administered sections of the Wechsler Intelligence Scale for Children-IV, the Delis Kaplan Executive Functioning Scales, the Test of Everyday Attention for Children, and the Wide Range Assessment of Memory and Learning--2nd Edition to assess neurocognitive function. The ESS and the CSHQ indicate that many participants had excessive daytime sleepiness and increased sleep-disordered breathing. Participants before therapy reflected neurocognitive deficiencies in all areas. Of the original 21 children, 4 completed the full PAP treatment and were reevaluated, demonstrating improvements in memory and motor speed. Children with OSAS reported sleep-disordered breathing, increased daytime sleepiness, and deficiencies in neurocognitive measures. Correcting these sleep impairments appeared to reduce global neurocognitive deficits while improving memory and processing speed.

Cognition in obstructive sleep apnea-hypopnea syndrome (OSAS): current clinical knowledge and the impact of treatment

Obstructive sleep apnea-hypopnea syndrome (OSAS) is characterized by the presence of disordered breathing events that occur during sleep, as well as symptoms such as sleepiness and snoring. OSAS is associated with a number of adverse health consequences, and a growing literature focuses on its cognitive correlates. Although research in this field is mixed, multiple studies indicate that OSAS patients show impairment in attention, memory, and executive function. Continuous positive airway pressure (CPAP) is the most effective and widely used treatment of OSAS, and supplemental medications may supplement CPAP treatment to ameliorate associated symptoms. Here, we review the literature on OSAS and cognition, including studies that have investigated the impact of CPAP and stimulant medication on cognitive performance in patients with OSAS. In general, no consistent effect of CPAP use on cognitive performance was evident. This may be due, in part, to variability in study design and sampling methodology across studies. Studies of stimulant medications generally reported positive effects on cognitive performance. We conclude with a discussion of the mechanisms that have been proposed to explain cognitive dysfunction in OSAS and directions for future research.

A Model for Studying Neuropsychological Effects of Sleep Intervention: The Effect of 3-week Continuous Positive Airway Pressure Treatment

PURPOSE: Patients with obstructive sleep apnea (OSA) commonly have cognitive complaints. There are few randomized studies that have examined neuropsychological effects of continuous positive airway pressure (CPAP) treatment in patients with OSA. In this double-blind trial, we examined if a 3-week CPAP treatment compared with placebo CPAP treatment has specific therapeutic effects on cognitive impairments in patients with OSA and if there are specific domains of cognitive impairments sensitive to 3-week CPAP treatment. SUBJECTS AND METHODS: Thirty-eight newly diagnosed patients with untreated OSA underwent neuropsychological testing before and after 3-weeks CPAP or Placebo CPAP treatment. The two treatment groups (therapeutic CPAP, and placebo-CPAP) were compared using repeated measures analysis of variance (ANOVA). RESULTS AND CONCLUSION: Impairments in neuropsychological functioning ranged from 2.6% to 47.1% before treatment. In response to 3 weeks of treatment, there was no significant time by treatment interaction for a global deficit score of neuropsychological functioning. Only the Stroop Color (number correct) test showed significant improvement specific to CPAP treatment. The study demonstrates the importance of further randomized placebo controlled studies in this area.

Auditory evoked potentials remain abnormal after CPAP treatment in patients with severe obstructive sleep apnoea

OBJECTIVE

To assess the effects of 3 months of optimal CPAP treatment on auditory event related potentials (AERP) in patients with severe obstructive sleep apnoea (OSA) compared with healthy controls.

METHODS

Auditory odd-ball related N1, P2, N2 and P3 AERP components were assessed in 9 severe OSA subjects and 9 healthy controls at baseline evaluation and at ∼3 months follow-up in both groups, with OSA subjects treated with continuous positive air-way pressure (CPAP) during this period.

RESULTS

Severe OSA subjects showed significantly delayed, P2, N2 and P3 latencies, and significantly different P2 and P3 amplitudes compared to controls at baseline (group effect, all p<0.05). At follow-up evaluation P3 latency shortened in treated OSA patients but remained prolonged compared to controls (group by treatment interaction, p<0.05) despite high CPAP compliance (6h/night). The earlier AERP (P2 and N2) components did not change in either controls or OSA patients at follow-up and remained different in patients versus controls.

CONCLUSIONS

This study demonstrates that in severe OSA patients AERP responses show minimal or no improvement and remain abnormal following 3 months of optimal CPAP treatment.

SIGNIFICANCE

Persistent cortical sensory processing abnormalities despite treatment in severe OSA may have implications for daytime neurobehavioral performance and safety in OSA patients. AERP responses may help identify residual performance deficits and risks.

Driving simulator performance remains impaired in patients with severe OSA after CPAP treatment

STUDY OBJECTIVES

To assess the effectiveness of CPAP treatment in improving 90-minute driving simulator performance in severe OSA patients compared to age/gender matched controls.

DESIGN

Driving simulator performance was assessed at baseline and 3 months later, with OSA patients treated with CPAP during the interval.

SETTING

University Teaching Hospital.

PARTICIPANTS

Patients with severe OSA (n = 11) and control subjects without OSA (n = 9).

INTERVENTIONS

CPAP MEASUREMENTS AND RESULTS: Simulator driving parameters of steering deviation, braking reaction time and crashes were measured at baseline and ∼3 months follow-up. At baseline, OSA subjects demonstrated significantly greater steering deviation compared to controls (mean [95% CI], OSA group, 49.9 cm [43.7 to 56.0 cm] vs control group, 34.9 cm [28.1 to 41.7 cm], p = 0.003). Following ∼3 months of CPAP treatment (mean ± SD 6.0 ± 1.4 h/night), steering deviation in OSA subjects improved by an average of 3.1 cm (CI, 1.4 to 4.9), p < 0.001, while no significant steering changes were observed in the control group. Despite the improvement, steering deviation in the OSA group remained significantly higher than in controls (OSA group, 46.7 cm [CI, 40.6 to 52.8 cm] vs control group, 36.1 cm [CI, 29.3 to 42.9 cm], p = 0.025).

CONCLUSIONS

While driving simulator performance improved after ∼3 months of CPAP treatment with high adherence in patients with severe OSA, performance remained impaired compared to control subjects. These results add to the growing body of evidence that some neurobehavioral deficits in patients with severe OSA are not fully reversed by treatment. Further studies are needed to assess causes of residual driving simulator impairment and to determine whether this is associated with persistent elevated real-life accident risk.

TRIAL REGISTRATION

Data presented in this manuscript was collected as part of a clinical trial "Experimental Investigations of Driving Impairment in Obstructive Sleep Apnoea" ACTRN12610000009011, http://www.anzctr.org.au/trial_view.aspx?ID=334979

The association between obstructive sleep apnea and neurocognitive performance--the Apnea Positive Pressure Long-term Efficacy Study (APPLES)

STUDY OBJECTIVES

To determine associations between obstructive sleep apnea (OSA) and neurocognitive performance in a large cohort of adults.

STUDY DESIGN

Cross-sectional analyses of polysomnographic and neurocognitive data from 1204 adult participants with a clinical diagnosis of obstructive sleep apnea (OSA) in the Apnea Positive Pressure Long-term Efficacy Study (APPLES), assessed at baseline before randomization to either continuous positive airway pressure (CPAP) or sham CPAP.

MEASUREMENTS

Sleep and respiratory indices obtained by laboratory polysomnography and several measures of neurocognitive performance.

RESULTS

Weak correlations were found for both the apnea hypopnea index (AHI) and several indices of oxygen desaturation and neurocognitive performance in unadjusted analyses. After adjustment for level of education, ethnicity, and gender, there was no association between the AHI and neurocognitive performance. However, severity of oxygen desaturation was weakly associated with worse neurocognitive performance on some measures of intelligence, attention, and processing speed.

CONCLUSIONS

The impact of OSA on neurocognitive performance is small for many individuals with this condition and is most related to the severity of hypoxemia.

Cognition and daytime functioning in sleep-related breathing disorders

Sleep-related breathing disorders encompass a range of disorders in which abnormal ventilation occurs during sleep as a result of partial or complete obstruction of the upper airway, altered respiratory drive, abnormal chest wall movement, or respiratory muscle function. The most common of these is obstructive sleep apnea (OSA), occurring in both adults and children, and causing significant cognitive and daytime dysfunction and reduced quality of life. OSA patients experience repetitive brief cessation of breathing throughout the night, which causes intermittent hypoxemia (reductions in hemoglobin oxygen levels) and fragmented sleep patterns. These nocturnal events result in excessive daytime sleepiness, and changes in mood and cognition. Chronic excessive sleepiness during the day is a common symptom of sleep-related breathing disorders, which is assessed in sleep clinics both subjectively (questionnaire) and objectively (sleep latency tests). Mood changes are often reported by patients, including irritability, fatigue, depression, and anxiety. A wide range of cognitive deficits have been identified in untreated OSA patients, from attentional and vigilance, to memory and executive functions, and more complex tasks such as simulated driving. These changes are reflected in patient reports of difficulty in concentrating, increased forgetfulness, an inability to make decisions, and falling asleep at the wheel of a motor vehicle. These cognitive changes can also have significant downstream effects on daily functioning. Moderate to severe cases of the disorder are at a higher risk of having a motor vehicle accident, and may also have difficulties at work or school. A number of comorbidities may also influence the cognitive changes in OSA patients, including hypertension, diabetes, and stroke. These diseases can cause changes to neural vasculature and result in neural damage, leading to cognitive impairments. Examination of OSA patients using neuroimaging techniques such as structural magnetic resonance imaging and proton magnetic resonance spectroscopy has observed significant changes to brain structure and metabolism. The downstream effects of neural, cognitive, and daytime functional impairments can be significant if left untreated. A better understanding of the cognitive effects of these disorders, and development of more effective assessment tools for diagnosis, will aid early intervention and improve quality of life of the patient.

Neural injury in sleep apnea

Sleepiness has long been recognized as a presenting symptom in obstructive sleep apnea syndrome, but persistent neurocognitive injury from sleep apnea has been appreciated only recently. Although therapy for sleep apnea markedly improves daytime symptoms, cognitive impairments may persist despite long-term therapy with continuous positive airway pressure. We know now that certain groups of neurons, typically those that are more metabolically active, are more vulnerable to injury than others. Animal models of sleep apnea oxygenation patterns have been instrumental in elucidating mechanisms of injury. The hypoxia/reoxygenation events result in oxidative, inflammatory, and endoplasmic reticulum stress responses in susceptible neural groups. With molecular pathways being fleshed out in animal models, it is time to carefully and systematically examine neural injury in humans and test the applicability of findings from animal models. To succeed, however, we cannot view sleep apnea as an isolated process. Rather, injury in sleep apnea is more likely the consequence of overlapping injuries from comorbid conditions. The progress in elucidating mechanisms of neural injury is palpable, and it now seems we indeed are closer to developing therapies to prevent and treat neural injury in obstructive sleep apnea.

Quantitative spectral analysis of vigilance EEG in patients with obstructive sleep apnoea syndrome: EEG mapping in OSAS patients

INTRODUCTION

Sleep disruption and blood gas abnormalities, observed in patients with obstructive sleep apnoea (OSA) syndrome, prevent sleep-related restorative processes and induce chemical or structural central nervous system cellular injury. The aim of the study was to determine electroencephalogram (EEG) alterations related to the severity of OSA in patients with OSAS and the effect of the nasal continuous positive air pressure (nCPAP) treatment.

MATERIALS AND METHODS

Polysomnography and vigilant EEGs were performed in subjects with possible OSA. The mean relative power was calculated for delta, theta, alpha and beta frequency bands. Thirty subjects without and 131 with OSA participated in this study. In 29 male patients with severe OSA, quantitative EEGs were re-evaluated after 6 months of CPAP treatment.

RESULTS

Compared to subjects without OSA, patients with severe OSA showed an increase in relative theta and delta power (occipital, temporal and parietal areas). Six months of nCPAP treatment improved daytime sleepiness of OSA patients. EEG demonstrated a decrease in alpha (frontal, central and temporal areas) and theta (frontal areas) relative power. However, beta relative power was increased mainly in central, and delta relative power, in all brain areas.

DISCUSSION

In conclusion, EEG slowing was observed in OSA patients. CPAP treatment improved daytime sleepiness of OSA patients in contrast to the alterations in alpha (decreased) and delta (increased) relative power suggesting a possible persistent brain dysfunction.

How treatment affects cognitive deficits in patients with sleep disorders: methodological issues and results

Sleep disorders are frequently associated with impaired performance although the type and extent of cognitive deficits varies widely between different types of sleep disorders. Treatment is expected to ameliorate these deficits. However, cognitive functioning and its change with treatment depend on numerous factors. In this chapter we discuss methodological issues, including test selection, and person-specific, task-specific and environmental factors that influence cognitive functioning. In addition, features of study design and sampling strategies are discussed. The chapter ends with a short overview of routes by which treatment may affect cognition in sleep-disordered patients.

Relationship between obstructive sleep apnea severity and brain activation during a sustained attention task

STUDY OBJECTIVES

The objectives of this study were to (1) characterize cognitive and cerebral correlates of attention and response speed in patients with obstructive sleep apnea (OSA) and (2) assess the association of performance and brain activation with measures of OSA severity.

DESIGN

Patients with OSA and controls were compared on performance and brain activation during a sustained attention task. The association of reaction time and brain activation with apnea-hypopnea index, nocturnal hypoxia, and arousals was assessed.

SETTING

Functional magnetic resonance imaging was conducted while participants performed a Go-No-Go task. The 'Go' trials of the Go-No-Go task were used to index attention processing.

PARTICIPANTS

Fourteen patients with OSA and 14 normal control subjects with equivalent age, body mass index, blood pressure, and education.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Patients with OSA showed decreased brain activation in cingulate, frontal, and parietal regions typically involved in attention tasks, compared with control subjects. Within the patients with OSA, increasing arousal index, but not desaturation index, was associated with slower mean reaction time and with decreased brain activation in areas involved in arousal and attention, response selection, motor response, and decision making. The apnea-hypopnea index, by itself, was not associated with changes in cerebral response.

CONCLUSIONS

Patients with OSA showed decreased brain activation compared with control subjects during an attention task. The association of arousal index (but not hypoxia) with slow reaction times and brain activation suggests that alertness and reaction times show greater correlations with measures of sleep disruption than with measures of hypoxia.

Recurrent apnea induces neuronal apoptosis in the guinea pig forebrain

Obstructive sleep apnea (OSA) and sleep-disordered breathing (SDB) can result in impaired cognition and mental acuity, and the generation of mood disorders, including depression. However, the mechanisms of neuronal damage for these complications have not been elucidated. Accordingly, using immunohistochemical technique with monoclonal antibody against single-stranded DNA, we examined the morphological effects of chronic recurrent apnea on neurons in the hippocampus and related forebrain sites in guinea pigs. Our results show that a large number of neurons labeled by anti-ssDNA antibody were present in the cingulate, insular and frontal cortices, the hippocampus and the amygdala in conjunction with periods of recurrent apnea. However, no labeling was observed in comparable regions of the brain in control guinea pigs. In the cortices of experimental animals, labeled neurons were detected mainly in the superficial layers (II-III) in the frontal, insular and cingulate cortex. In the hippocampus, most labeled neurons were located in the CA1 region, in which most of stained neurons were observed in strata pyramidal, while only a few positive neurons were located in the strata radiatum and the strata oriens. In addition, a large number of labeled neurons were also detected in the central nucleus of amygdala in the guinea pigs underwent recurrent periods of apnea. The present data indicate that recurrent apnea results in cell death in the hippocampus and related forebrain regions via mechanisms of apoptosis, which may represent the basis for the clinical complications of obstructive sleep apnea and sleep-disordered breathing.

Cognitive effects of treating obstructive sleep apnea in Alzheimer's disease: a randomized controlled study

OBJECTIVES

To examine whether treatment of obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) in patients with Alzheimer's disease (AD) results in better cognitive function.

DESIGN

Randomized double-blind placebo-controlled trial. Participants were randomized to therapeutic CPAP for 6 weeks or placebo CPAP for 3 weeks followed by therapeutic CPAP for 3 weeks.

SETTING

General clinical research center.

PARTICIPANTS

Fifty-two men and women with mild to moderate AD and OSA.

INTERVENTION

CPAP.

MEASUREMENTS

A complete neuropsychological test battery was administered before treatment and at 3 and at 6 weeks.

RESULTS

A comparison of subjects randomized to 3 weeks of therapeutic versus placebo CPAP suggested no significant improvements in cognition. A comparison of pre- and posttreatment neuropsychological test scores after 3 weeks of therapeutic CPAP in both groups showed a significant improvement in cognition. The study was underpowered to make definitive statements about improvements within specific cognitive constructs, although exploratory post hoc examination of change scores for individual tests suggested improvements in episodic verbal learning and memory and some aspects of executive functioning such as cognitive flexibility and mental processing speed.

CONCLUSION

OSA may aggravate cognitive dysfunction in dementia and thus may be a reversible cause of cognitive loss in patients with AD. OSA treatment seems to improve some cognitive functioning. Clinicians who care for patients with AD should consider implementing CPAP treatment when OSA is present.

Abnormal respiratory-related evoked potentials in untreated awake patients with severe obstructive sleep apnoea syndrome

AIM

Obstructive sleep apnoeas generate an intense afferent traffic leading to arousal and apnoea termination. Yet a decrease in the sensitivity of the afferents has been described in patients with obstructive sleep apnoea, and could be a determinant of disease severity. How mechanical changes within the respiratory system are processed in the brain can be studied through the analysis of airway occlusion-related respiratory-related evoked potentials. Respiratory-related evoked potentials have been found altered during sleep in mild and moderate obstructive sleep apnoea syndrome, with contradictory results during wake. We hypothesized that respiratory-related evoked potentials' alterations during wake, if indeed a feature of the obstructive sleep apnoea syndrome, should be present in untreated severe patients.

METHODS

Ten untreated patients with severe obstructive sleep apnoea syndrome and eight matched controls were studied. Respiratory-related evoked potentials were recorded in Cz-C3 and Cz-C4, and described in terms of the amplitudes and latencies of their components P1, N1, P2 and N2.

RESULTS

Components amplitudes were similar in both groups. There was no significant difference in P1 latencies. This was also the case for N1 in Cz-C3. In contrast, N1 latencies in Cz-C4 were significantly longer in patients with obstructive sleep apnoea syndrome [median 98 ms (interquartile range 16.00) versus 79.5 ms (5.98), P = 0.015]. P2 and N2 were also significantly delayed, on both sides.

CONCLUSIONS

The cortical processing of airway occlusion-related afferents seems abnormal in untreated patients with severe obstructive sleep apnoea syndrome. This could be either a severity marker and/or an aggravating factor.

Armodafinil improves wakefulness and long-term episodic memory in nCPAP-adherent patients with excessive sleepiness associated with obstructive sleep apnea

Residual excessive sleepiness (ES) and impaired cognition can occur despite effective and regular nasal continuous positive airway pressure (nCPAP) therapy in some patients with obstructive sleep apnea (OSA). A pooled analysis of two 12-week, randomized, double-blind studies in nCPAP-adherent patients with ES associated with OSA evaluated the effect of armodafinil on wakefulness and cognition. Three hundred and ninety-one patients received armodafinil (150 or 250 mg) and 260 patients received placebo once daily for 12 weeks. Efficacy assessments included the Maintenance of Wakefulness Test (MWT), Cognitive Drug Research cognitive performance battery, Epworth Sleepiness Scale, and Brief Fatigue Inventory. Adverse events were monitored. Armodafinil increased mean MWT sleep latency from baseline to final visit by 2.0 min vs a decrease of 1.5 min with placebo (P < 0.0001). Compared with placebo, armodafinil significantly improved quality of episodic secondary memory (P < 0.05) and patients' ability to engage in activities of daily living (P < 0.0001) and reduced fatigue (P < 0.01). The most common adverse events were headache, nausea, and insomnia. Armodafinil did not adversely affect desired nighttime sleep, and nCPAP use remained high (approximately 7 h/night). Adjunct treatment with armodafinil significantly improved wakefulness, long-term memory, and patients' ability to engage in activities of daily living in nCPAP-adherent individuals with ES associated with OSA. Armodafinil also reduced patient-reported fatigue and was well tolerated.