Katia Gagnon

Regional Cerebral Blood Flow during Wakeful Rest in Older Subjects with Mild to Severe Obstructive Sleep Apnea.

OBJECTIVES To evaluate changes in regional cerebral blood flow (rCBF) during wakeful rest in older subjects with mild to severe obstructive sleep apnea (OSA) and healthy controls, and to identify markers of OSA severity that predict altered rCBF. DESIGN High-resolution (99m)Tc-HMPAO SPECT imaging during wakeful rest. SETTING Research sleep laboratory affiliated with a University hospital. PARTICIPANTS Fifty untreated OSA patients aged between 55 and 85 years, divided into mild, moderate, and severe OSA, and 20 age-matched healthy controls. INTERVENTIONS N/A. MEASUREMENTS Using statistical parametric mapping, rCBF was compared between groups and correlated with clinical, respiratory, and sleep variables. RESULTS Whereas no rCBF change was observed in mild and moderate groups, participants with severe OSA had reduced rCBF compared to controls in the left parietal lobules, left precentral gyrus, bilateral postcentral gyri, and right precuneus. Reduced rCBF in these regions and in areas of the bilateral frontal and left temporal cortex was associated with more hypopneas, snoring, hypoxemia, and sleepiness. Higher apnea, microarousal, and body mass indexes were correlated to increased rCBF in the basal ganglia, insula, and limbic system. CONCLUSIONS While older individuals with severe obstructive sleep apnea (OSA) had hypoperfusion in the sensorimotor and parietal areas, respiratory variables and subjective sleepiness were correlated with extended regions of hypoperfusion in the lateral cortex. Interestingly, OSA severity, sleep fragmentation, and obesity correlated with increased perfusion in subcortical and medial cortical regions. Anomalies with such a distribution could result in cognitive deficits and reflect impaired vascular regulation, altered neuronal integrity, and/or undergoing neurodegenerative processes.

Quantitative EEG of Rapid-Eye-Movement Sleep A Marker of Amnestic Mild Cognitive Impairment

The basal forebrain cholinergic system, which is impaired in early Alzheimer’s disease, is more crucial for the activation of rapid-eye-movement (REM) sleep electroencephalogram (EEG) than it is for wakefulness. Quantitative EEG from REM sleep might thus provide an earlier and more accurate marker of the development of Alzheimer’s disease in subjects with mild cognitive impairment (MCI) subjects than that from wakefulness. To assess the superiority of the REM sleep EEG as a screening tool for preclinical Alzheimer’s disease, 22 subjects with amnestic MCI (a-MCI; 63.9 ± 7.7 years), 10 subjects with nonamnestic MCI (na-MCI; 64.1 ± 4.5 years) and 32 controls (63.7 ± 6.6 years) participated in the study. Spectral analyses of the waking EEG and REM sleep EEG were performed and the [(delta + theta)/(alpha + beta)] ratio was used to assess between-group differences in EEG slowing. The a-MCI subgroup showed EEG slowing in frontal lateral regions compared to both na-MCI and control groups. This EEG slowing was present in wakefulness (compared to controls) but was much more prominent in REM sleep. Moreover, the comparison between amnestic and nonamnestic subjects was found significant only for the REM sleep EEG. There was no difference in EEG power ratio between na-MCI and controls for any of the 7 cortical regions studied. These findings demonstrate the superiority of the REM sleep EEG in the discrimination between a-MCI and both na-MCI and control subjects.

Are NREM sleep characteristics associated to subjective sleep complaints after mild traumatic brain injury

INTRODUCTION Sleep complaints are common after mild traumatic brain injury (mTBI). While recent findings suggest that sleep macro-architecture is preserved in mTBI, features of non-rapid eye movement (NREM) sleep micro-architecture including electroencephalography (EEG) spectral power, slow waves (SW), and sleep spindles could be affected. This study aimed to compare NREM sleep in mTBI and healthy controls, and explore whether NREM sleep characteristics correlate with sleep complaints in these groups. METHODS Thirty-four mTBI participants (mean age: 34.2 ± 11.9 yrs; post-injury delay: 10.5 ± 10.4 weeks) and 29 age-matched controls (mean age: 32.4 ± 8.2 yrs) were recruited for two consecutive nights of polysomnographic (PSG) recording. Spectral power was computed and SW and spindles were automatically detected in three derivations (F3, C3, O1) for the first three sleep cycles. Subjective sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI). RESULTS mTBI participants reported significant poorer sleep quality than controls on the PSQI and showed significant increases in beta power during NREM sleep at the occipital derivation only. Conversely, no group differences were found in SW and spindle characteristics. Interestingly, changes in NREM sleep characteristics were not associated with mTBI estimation of sleep quality. CONCLUSIONS Compared to controls, mTBI were found to have enhanced NREM beta power. However, these changes were not found to be associated with the subjective evaluation of sleep. While increases in beta bands during NREM sleep may be attributable to the occurrence of a brain injury, they could also be related to the presence of pain and anxiety as suggested in one prior study.

Gray Matter Hypertrophy and Thickening with Obstructive Sleep Apnea in Middle-aged and Older Adults

Rationale: Obstructive sleep apnea causes intermittent hypoxemia, hemodynamic fluctuations, and sleep fragmentation, all of which could damage cerebral gray matter that can be indirectly assessed by neuroimaging. Objectives: To investigate whether markers of obstructive sleep apnea severity are associated with gray matter changes among middle‐aged and older individuals. Methods: Seventy‐one subjects (ages, 55‐76 yr; apnea‐hypopnea index, 0.2‐96.6 events/h) were evaluated by magnetic resonance imaging. Two techniques were used: (1) voxel‐based morphometry, which measures gray matter volume and concentration; and (2) FreeSurfer (an open source software suite) automated segmentation, which estimates the volume of predefined cortical/subcortical regions and cortical thickness. Regression analyses were performed between gray matter characteristics and markers of obstructive sleep apnea severity (hypoxemia, respiratory disturbances, and sleep fragmentation). Measurements and Main Results: Subjects had few symptoms, that is, sleepiness, depression, anxiety, and cognitive deficits. Although no association was found with voxel‐based morphometry, FreeSurfer revealed increased gray matter with obstructive sleep apnea. Higher levels of hypoxemia correlated with increased volume and thickness of the left lateral prefrontal cortex as well as increased thickness of the right frontal pole, the right lateral parietal lobules, and the left posterior cingulate cortex. Respiratory disturbances positively correlated with right amygdala volume, and more severe sleep fragmentation was associated with increased thickness of the right inferior frontal gyrus. Conclusions: Gray matter hypertrophy and thickening were associated with hypoxemia, respiratory disturbances, and sleep fragmentation. These structural changes in a group of middle‐aged and older individuals may represent adaptive/reactive brain mechanisms attributed to a presymptomatic stage of obstructive sleep apnea.

Abnormal occipital event-related potentials in Parkinson's disease with concomitant REM sleep behavior disorder

BACKGROUND Rapid eye movement sleep behavior disorder is found in 33-46% of patients with Parkinsons disease and was shown to be associated with cognitive deficits. Our goal was to improve our understanding of the role of this sleep disorder in cerebral dysfunction occurring in Parkinsons disease using a visual cognitive task and event-related potentials. METHODS Sixteen patients with Parkinsons disease and rapid eye movement sleep behavior disorder, 15 patients with Parkinsons disease without rapid eye movement sleep behavior disorder and 16 healthy control subjects were included. The amplitude and latency of event-related potentials were compared between groups. RESULTS No group differences were found for reaction times or accuracy. A Group effect was found for P2 wave amplitude; patients with rapid eye movement sleep behavior disorder had increased P2 in comparison with the control group (p < 0.05). Patients with Parkinsons disease alone were not different from the two other groups for this component. Prolonged novelty P3 latencies on Cz were associated with longer disease durations among patients with Parkinsons disease (p < 0.01). CONCLUSION Co-morbid Parkinsons disease and rapid eye movement sleep behavior disorder were associated with abnormal visual P2 component of event-related potentials. Although patients with Parkinsons disease alone were not significantly different from patients with combined Parkinsons disease and rapid eye movement sleep behavior disorder, their P2 amplitudes were not sufficiently abnormal to differ from that of control subjects. This study confirms that rapid eye movement sleep behavior disorder accentuates cerebral dysfunctions in Parkinsons disease.

Association between waking electroencephalography and cognitive event-related potentials in patients with obstructive sleep apnea.

OBJECTIVE Sleepiness, cognitive deficits, abnormal event-related potentials (ERP), and slowing of the waking electroencephalography (EEG) activity have been reported in patients with obstructive sleep apnea (OSA). Our study aimed at evaluating if an association exists between the severity of ERP abnormalities and EEG slowing to better understand cerebral dysfunctions in OSA. METHODS Twelve OSA patients and 12 age-matched controls underwent an overnight polysomnographic recording, an EEG recording of 10 min of wakefulness, and an auditory ERP protocol known to specifically recruit attention. P300 and P3a ERP components were measured as well as the spectral power in each frequency band of the waking EEG. Pearson product moment correlations were used to measure associations between ERP characteristics and EEG spectral power in OSA patients and control subjects. RESULTS A positive correlation between the late P300 amplitude and θ power in the occipital region was observed in OSA subjects (P<.01). A positive correlation was also found between P3a amplitude and β1 power in central region in OSA subjects (P<.01). No correlation was observed for control subjects. CONCLUSIONS ERP abnormalities observed in an attention task are associated with a slowing of the waking EEG recorded at rest in OSA.

Detection of mild cognitive impairment in middle-aged and older adults with obstructive sleep apnea

Obstructive sleep apnoea increases the risk for mild cognitive impairment and dementia. The present study aimed to characterise the ability of two cognitive screening tests, the Mini-Mental State Examination and the Montreal Cognitive Assessment, to detect mild cognitive impairment in adults aged 55–85 years with and without obstructive sleep apnoea. We included 42 subjects with mild and 67 subjects with moderate-to-severe obstructive sleep apnoea. We compared them to 22 control subjects. Mild cognitive impairment was diagnosed by a comprehensive neuropsychological assessment. We used receiver operating characteristic curves to assess the ability of the two screening tests to detect mild cognitive impairment. The two screening tests showed similar discriminative ability in control subjects. However, among the mild and the moderate-to-severe obstructive sleep apnoea groups, the Mini-Mental State Examination was not able to correctly identify subjects with mild cognitive impairment. The Montreal Cognitive Assessments discriminant ability was acceptable in both sleep apnoea groups and was comparable to what was observed in controls. The Mini-Mental State Examination should not be used to screen for cognitive impairment in patients with obstructive sleep apnoea. The Montreal Cognitive Assessment could be used in clinical settings. However, clinicians should refer patients for neuropsychological assessment when neurodegenerative processes are suspected. The Montreal Cognitive Assessment performs better than the Mini-Mental State Examination in detecting cognitive impairment in individuals with obstructive sleep apnoea http://ow.ly/8gLS30lxjZk