The impact of study type and sleep measurement on oxygen desaturation index calculation.

STUDY OBJECTIVES: The oxygen desaturation index (ODI) is an important measure of sleep-disordered breathing during polysomnography (PSG); however, the AASM Manual (V3) does not specify whether to include oxygen desaturations occurring during wake epochs. Additionally, an ODI obtained from PSG can differ from an ODI using home sleep apnea tests (HSATs) that do not measure sleep, hampering diagnostic and treatment decision reliability. This study aimed to (1) compare an ODI that included all desaturations with an ODI that excluded desaturations occurring during wake epochs in PSG and (2) compare ODIs obtained from PSG with HSAT. METHODS: 100 consecutive PSGs for investigation of obstructive sleep apnea were compared. ODIs were calculated including all desaturations (ODIall) and by excluding desaturations entirely during wake epochs (ODIsleep). Additionally, we compared ODIall with an ODI calculated using monitoring time as the denominator (ODIHSAT). RESULTS: The median (interquartile range) 3% ODI for ODIall was 22.8 (13.1, 44.1) events/h and ODIsleep was 17.6 (11.5, 35.2) events/h (median difference: -3.9 events/h [-8.2, -0.9]; 21.0% [8.7%, 33.2%]). This discrepancy was larger with increasing ODI and decreasing sleep efficiency. The ODIHSAT was 17.4 (11.3, 35.2) events/h and the median reduction in ODIHSAT vs ODIall was -4.5 (-10.9, -2.0) events/h (21.6%; 11.1%, 33.8). CONCLUSIONS: ODI was significantly reduced when desaturations in wake epochs were excluded, and when ODI was based on monitoring time rather than sleep time, with the potential for underestimation of disease severity. Results suggest that ODI can differ substantially depending on the calculation and study type used, and that there is a need for standardization to ensure consistent diagnosis and treatment outcomes. CITATION: Whenn CB, Wilson DL, Ruehland WR, Churchward TJ, Worsnop C, Tolson J. The impact of study type and sleep measurement on oxygen desaturation index calculation. J Clin Sleep Med. 2024;20(5):709-717.

Associations Between Amyloid Burden, Hypoxemia, Sleep Architecture, and Cognition in Obstructive Sleep Apnea.

BACKGROUND: Obstructive sleep apnea (OSA) is associated with an increased risk of amyloid-ß (Aß) burden, the hallmark of Alzheimer's disease, and cognitive decline. OBJECTIVE: To determine the differential impacts of hypoxemia and slow-wave sleep disruption on brain amyloid burden, and to explore the effects of hypoxemia, slow-wave sleep disruption, and amyloid burden on cognition in individuals with and without OSA. METHODS: Thirty-four individuals with confirmed OSA (mean±SD age 57.5±4.1 years; 19 males) and 12 healthy controls (58.5±4.2 years; 6 males) underwent a clinical polysomnogram, a NAV4694 positron emission tomography (PET) scan for Aß burden, assessment of APOEɛ status and cognitive assessments. Linear hierarchical regressions were conducted to determine the contributions of demographic and sleep variables on amyloid burden and cognition. RESULTS: Aß burden was associated with nocturnal hypoxemia, and impaired verbal episodic memory, autobiographical memory and set shifting. Hypoxemia was correlated with impaired autobiographical memory, and only set shifting performance remained significantly associated with Aß burden when controlling for sleep variables. CONCLUSIONS: Nocturnal hypoxemia was related to brain Aß burden in this sample of OSA participants. Aß burden and hypoxemia had differential impacts on cognition. This study reveals aspects of sleep disturbance in OSA that are most strongly associated with brain Aß burden and poor cognition, which are markers of early Alzheimer's disease. These findings add weight to the possibility that hypoxemia may be causally related to the development of dementia; however, whether it may be a therapeutic target for dementia prevention in OSA is yet to be determined.

Improved depressive symptoms, and emotional regulation and reactivity, in individuals with obstructive sleep apnea after short- and long-term CPAP therapy use.

Obstructive Sleep Apnoea (OSA) is associated with high rates of depression; however, if and how treatment of OSA improves depressive symptoms is unclear. To further understand this link we considered the role of emotional regulation - the ability to control and express our emotional responses - thought to be a central component of depression. This study aimed to assess changes in depressive symptoms and emotional responses in individuals with OSA after 4- and 12-months of continuous positive airway pressure (CPAP) treatment. One-hundred and twenty-one OSA participants (50 female, Mage = 51.93; mean AHI = 36.27) were recruited from a tertiary clinical sleep service prior to CPAP initiation, and randomised to either a CPAP group or a 4 month wait-list group. Participants completed the Center for Epidemiological Studies Depression Scale, the Emotional Reactivity Scale and the Difficulties in Emotion Regulation Scale at baseline, and 1-, 2-, and 4-months follow-up. The CPAP group also completed the questionnaires 12-months after CPAP initiation. CPAP use at 1 month and 12 months was 5.1h/night and 4.9h/night, respectively. Significant improvements in depressive symptoms, emotional regulation and reactivity, and subjective sleepiness were observed after 4 months in both groups, however, the within group changes were only significant for those using CPAP. After 12-months of CPAP treatment, these improvements were maintained. There was no association between CPAP treatment adherence and improvements in any outcome. CPAP treatment for 12 months may reduce symptoms of depression and improve emotional regulation in individuals with OSA.

A randomized controlled trial of a multi-dimensional intervention to improve CPAP use and self-efficacy.

OBJECTIVES: To assess the utility of a tailored intervention program to improve continuous positive airway pressure (CPAP) use and self-efficacy in individuals with obstructive sleep apnea (OSA). METHODS: 81 participants (mean age 52.1 ± 11.6 years; 35 females) with OSA were randomized to either a multi-dimensional intervention (PSY CPAP, n = 38) or treatment as usual (TAU CPAP, n = 43). The intervention included a psychoeducation session prior to CPAP initiation, a booster psychoeducation session in the first weeks of commencing CPAP, follow-up phone calls on days 1 and 7, and a review appointment on day 14. CPAP use was compared between the PSY CPAP and TAU CPAP groups at 1 week, 1 month, and 4 months. Self-efficacy scores (risk perception, outcome expectancies, and CPAP self-efficacy) were compared between groups following the initial psychoeducation session and again at 1 month and 4 months. RESULTS: CPAP use was higher in the PSY CPAP group compared to the TAU CPAP group for all time points (p = .02). Outcome expectancies improved significantly over time in PSY CPAP participants (p = .007). Change in risk perception was associated with CPAP use at 1 week (p = .02) for PSY CPAP participants. However, risk perception did not mediate the effect between group and CPAP use at 1 week. CONCLUSIONS: Interventions designed to increase self-efficacy and administered prior to CPAP initiation, repeated in the early stages of CPAP therapy, and combined with a comprehensive follow-up regime are likely to improve CPAP use. Sustained improvement in CPAP use is the ultimate goal but remains to be investigated.

Filters Alter the Performance of Noninvasive Ventilators.

BACKGROUND: Noninvasive ventilation is recommended in hypercapnic respiratory failure secondary to ventilatory failure. Noninvasive ventilation may contribute to aerosol dispersion, which may increase the risk of transmission of COVID 2019. The addition of filters to the ventilator circuit has been recommended to reduce this risk. The aim of this benchtop study was to investigate the impact of adding filters to a ventilator circuit. METHODS: In this benchtop study, a breathing simulator was used with 4 commonly used ventilators. Ventilators were set to approximate the typical settings that are used for patients on long-term noninvasive ventilation. Ventilator performance was then evaluated with 3 circuit configurations in place: circuit A: no filter in situ; circuit B: 1 filter at the simulator end of the circuit; and circuit C: 1 filter at the simulator end of the circuit and a second filter at the ventilator end of the circuit. RESULTS: Ventilator variables were impacted by the addition of filters. Measurements of peak pressure (P < .001), tidal volume (P < .001), and peak flow (P < .001) decreased between circuit A and circuit C in all ventilators that were tested. Ventilator triggering was less sensitive in 3 of the 4 ventilators and the fourth ventilator did not trigger under the same simulator settings. CONCLUSIONS: This study demonstrated that ventilator settings established with filters in situ are not applicable if the ventilator is used without the filters. This is an important clinical consideration for patients who are hospitalized and require noninvasive ventilation in the COVID 2019 era.

Exclusion of EEG-based arousals in wake epochs of polysomnography leads to underestimation of the arousal index.

STUDY OBJECTIVES: There is an internal contradiction in current American Academy of Sleep Medicine standards for arousal index (AI) calculation in polysomnography: Arousals in sleep and wake epochs are counted, but only sleep time is used in the denominator. This study aimed to investigate the impact of including arousals scored in wake epochs on the AI. METHODS: We compared AIs including (AIinc) vs excluding (AIexc) awake-epoch arousals from 100 consecutive polysomnograms conducted for investigation of possible obstructive sleep apnea. To determine the AI that most closely approximated "truth," AIinc and AIexc were compared to an AI calculated from continuous sleep analysis (AIcont) in a 20-polysomnogram subgroup of patients. RESULTS: The median (interquartile range) increase in AIinc was 5.2 events/h (3.5-8.1) vs AIexc (AIinc = 28.0 events/h [18.4-38.9] vs AIexc = 22.9 events/ h [13.1-31.3]), equating to an increase of 25.3% (15.6-40.8). As the AI increased, the difference increased (P < .001), with decreasing sleep efficiency and an increasing apnea-hypopnea index as the strongest predictors of the difference between AIexc and AIinc. The absolute AIexc-AIcont difference (7.7 events/h [5.1-13.6]) was significantly greater than the AIinc-AIcont difference (1.2 events/h [0.6-5.7]; z = -3.099; P = .002). CONCLUSIONS: There was a notable increase in AI when we included wake-epoch arousals, particularly in patients with more severe obstructive sleep apnea or reduced sleep efficiency. However, the AI including wake-epoch arousals best matched the "true" continuous sleep-scoring AI. Our study informs clinical and research practice, highlights epoch scoring pitfalls, and supports the current American Academy of Sleep Medicine standard arousal reporting approach for future standards. CITATION: Wilson DL, Tolson J, Churchward TJ, Melehan K, O'Donoghue FJ, Ruehland WR. Exclusion of EEG-based arousals in wake epochs of polysomnography leads to underestimation of the arousal index. J Clin Sleep Med. 2022;18(5):1385-1393.

Does continuous positive airways pressure treatment improve clinical depression in obstructive sleep apnea? A randomized wait-list controlled study.

BACKGROUND: Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder that is associated with a range of adverse daytime sequelae, including significantly higher rates of clinical depression than is seen in the general community. Improvements in depressive symptoms occur after treatment of the primary sleep disorder, suggesting that comorbid depression might be an intrinsic feature of OSA. However, there are limited data on whether treatment for OSA in patients diagnosed with clinical depression improves mood symptoms meaningfully enough to lead to the remission of the psychiatric diagnosis. METHODS: N = 121 untreated OSA patients were randomized to either continuous positive airway pressure (CPAP) treatment or waitlist control, and depressive symptoms, sleepiness and clinical depression (using a structured clinical interview) were assessed at baseline and 4 months. Linear and logistic regression analyses were conducted, controlling for baseline scores, stratification factors and antidepressant use. RESULTS: Depressive symptoms (odds ratio [OR] = -4.19; 95% confidence interval [CI] = -7.25, -1.13; p = .008) and sleepiness (OR = -4.71; 95% CI = -6.26, -3.17; p < .001) were significantly lower at 4 months in the CPAP group compared to waitlist. At 4 months, there was a significant reduction in the proportion of participants in the CPAP group meeting criteria for clinical depression, compared to the waitlist controls (OR = 0.06, 95% CI = 0.01, 0.37; p = .002). CONCLUSION: Treatment of OSA may be a novel approach for the management and treatment of clinical depression in those with comorbid sleep disordered breathing. Larger trials of individuals with clinical depression and comorbid OSA are needed.

Clinical depression in untreated obstructive sleep apnea: examining predictors and a meta-analysis of prevalence rates.

OBJECTIVE/BACKGROUND: Patients with obstructive sleep apnea (OSA) experience daytime sleepiness, cognitive impairment and depressive symptoms. However, the measured prevalence of clinical depression in OSA using standardized clinical assessment is currently unclear. The aims of this study were to examine the prevalence of clinical depression and antidepressant use in untreated OSA patients, to examine predictors of depression, and to conduct an exploratory meta-analysis to determine the pooled prevalence of clinical depression in this population. PATIENTS/METHODS: In sum, 109 consecutive patients with diagnosed OSA (mean age (SD) = 52.6 (12.1) years; 43.1% female) who presented to the sleep laboratory completed a structured clinical interview for depression (SCID-IV), the Hospital Anxiety and Depression Scale, the Pittsburgh Sleep Quality Index (PSQI), the Functional Outcomes of Sleep Questionnaire (FOSQ), the Assessment of Quality of Life Questionnaire (AQoL) and the Epworth Sleepiness Scale (EES). An exploratory meta-analysis was also conducted to quantify the risk of clinical depression in untreated OSA. RESULTS: Twenty-five (22.7%) participants had clinical depression based on the SCID-IV, and 24.8% were using antidepressants. Those with clinical depression had significantly poorer sleep quality and impaired quality of life. In a regression model, quality of life impairment was most strongly associated with clinical depression. Results from the meta-analysis revealed a pooled prevalence of 23% of clinical depression in OSA patients across seven studies. CONCLUSION: Clinical depression and antidepressant use is common in patients with OSA. Depression was associated with reduced quality of life and poorer subjective sleep, however it was not associated with polysomnographic measures or daytime sleepiness. Whether CPAP treatment can alleviate the burden of clinical depression needs to be determined in future studies.

Apnoea and hypopnoea scoring for people with spinal cord injury: new thresholds for sleep disordered breathing diagnosis and severity classification.

STUDY DESIGN: Descriptive study. OBJECTIVES: To determine the effect of respiratory event rule-set changes on the apnoea hypopnoea index, and diagnostic and severity thresholds in people with acute and chronic spinal cord injury. SETTING: Eleven acute spinal cord injury inpatient hospitals across Australia, New Zealand, Canada and England; community dwelling chronic spinal cord injury patients in their own homes. METHODS: Polysomnography of people with acute (n = 24) and chronic (n = 78) tetraplegia were reanalysed from 1999 American Academy of Sleep Medicine (AASM) respiratory scoring, to 2007 AASM 'alternative' and 2012 AASM respectively. Equivalent cut points for published 1999 AASM sleep disordered breathing severity ranges were calculated using receiver operator curves, and results presented alongside analyses from the able-bodied. RESULTS: In people with tetraplegia, shift from 1999 AASM to 2007 AASM 'alternative' resulted in a 22% lower apnoea hypopnoea index, and to 2012 AASM a 17% lower index. In people with tetraplegia, equivalent cut-points for 1999 AASM severities of 5,15 and 30 were calculated at 2.4, 8.1 and 16.3 for 2007 AASM 'alternative' and 3.2, 10.0 and 21.2 for 2012 AASM. CONCLUSION: Interpreting research, prevalence and clinical polysomnography results conducted over different periods requires knowledge of the relationship between different rule-sets, and appropriate thresholds for diagnosis of disease. SPONSORSHIP: This project was proudly supported by the Traffic Accident Commission (Program grant) and the National Health and Medical Research Council (PhD stipend 616605).

Worth the effort? Weighing up the benefit and burden of continuous positive airway pressure therapy for the treatment of obstructive sleep apnoea in chronic tetraplegia.

STUDY DESIGN: Mixed methods OBJECTIVES: Continuous positive airway pressure (CPAP) therapy is the recommended treatment for obstructive sleep apnoea (OSA). The aim of this study was to estimate CPAP adherence in people with tetraplegia and OSA, and to explore the barriers and facilitators to CPAP use. SETTING: Hospital outpatient department in Melbourne, Australia METHODS: People with chronic tetraplegia and OSA were commenced with auto-titrating CPAP and supported for 1 month. Semi-structured interviews were conducted with participants at one month and analysed thematically. CPAP usage was measured at 1, 6 and 12 months, with "adherent" defined as achieving more than 4 h average per night. RESULTS: Sixteen participants completed the study (80% male; mean age 56 (SD = 15)). Mean nightly CPAP use at one month was 3.1 h (SD = 2.5; 38% adherent), and at 6 months and 12 months were 2.6 h (SD = 2.8; 25% adherent) and 2.1 h (SD = 3.2; 25% adherent). The perceived benefit/burden balance strongly influenced ongoing use. Burden attributed to CPAP use was common, and included mask discomfort, and physical and emotional problems. Adherent participants were motivated by the immediate daytime benefits to mood, alertness and sleepiness. There was a tendency to not recognise symptoms of OSA until after they were treated. CONCLUSION: CPAP use is challenging for people with tetraplegia, who experience substantial burden from using the device. When tolerated, the proximate benefits are substantial. People with tetraplegia need more intensive support for longer to help them overcome the burdens of CPAP and benefit from the treatment.