Relationship between Clinical and Polysomnography Measures Corrected for CPAP Use

Effects of obstructive sleep apnea during rapid eye movement sleep on cardiac autonomic dysfunction: Results from the Shanghai sleep health study cohort

In our large-scale study, the correlation between obstructive sleep apnea (OSA) related to rapid eye movement (REM) sleep and cardiac autonomic dysfunction was assessed by standard polysomnography (PSG). Cardiac autonomic dysfunction was evaluated by the measurement of heart rate variability (HRV). The cardiovascular disease (CVD) risk was determined using the cross-sectional prevalence of CVD and its overall 10 year risk according to the Framingham risk score (FRS). 4152 individuals were included in the study. A higher apnea-hypopnea index during REM sleep (AHIREM ) was correlated with increased CVD risk. The adjusted odds ratios (95% CIs) for CVD prevalence and its high 10 year risk in participants having severe OSA during REM sleep (AHIREM  ≥30 events/h) were 1.452 (1.012-2.084) and 1.904 (1.470-2.466) in the demographic adjusted model and 1.175 (0.810-1.704) and 1.716 (1.213-2.427) in the multivariate adjusted model, respectively, compared with the group with a AHIREM of <5 events/h. Fully adjusted multivariate linear regression models showed the independent association between AHIREM and a more elevated ratio of low-frequency and high-frequency (LF/HF) and LF in normalised units [LF (n.u.)] (P = 0.042, P = 0.027 in all participants and P = 0.033, P = 0.029 in participants with AHI during non-REM sleep <5 events/h, respectively). Mediation analysis demonstrated that OSA during REM sleep and CVD risk was significantly mediated by LF/HF and LF (n.u.). OSA during REM sleep may be a marker behind CVD risk because it promotes cardiac autonomic dysfunction.

Mean disease alleviation between surgery and continuous positive airway pressure in matched adults with obstructive sleep apnea

STUDY OBJECTIVES

Polysomnography parameters measure treatment efficacy for obstructive sleep apnea (OSA), such as reduction in apnea-hypopnea index (AHI). However, for continuous positive airway pressure (CPAP) therapy, polysomnography measures do not factor in adherence and thus do not measure effectiveness. Mean disease alleviation (MDA) corrects polysomnography measures for CPAP adherence and was used to compare treatment effectiveness between CPAP and multilevel upper airway surgery.

METHODS

This retrospective cohort study consisted of a consecutive sample of 331 patients with OSA managed with multilevel airway surgery as second-line treatment (N = 97) or CPAP (N = 234). Therapeutic effectiveness (MDA as % change or as corrected change in AHI) was calculated as the product of therapeutic efficacy (% or absolute change in AHI) and adherence (% time on CPAP of average nightly sleep). Cardinality and propensity score matching was utilized to manage confounding variables.

RESULTS

Surgery patients achieved greater MDA % than CPAP users (67 ± 30% vs. 60 ± 28%, p = 0.04, difference 7 ± 3%, 95% confidence interval 4% to 14%) in an unmatched comparison, despite a lower therapeutic efficacy seen with surgery. Cardinality matching demonstrated comparable MDA % in surgery (64%) and CPAP (57%) groups (p = 0.14, difference 8 ± 5%, 95% confidence interval -18% to 3%). MDA measured as corrected change in AHI showed similar results.

CONCLUSIONS

In adult patients with OSA, multilevel upper airway surgery and CPAP provide comparable therapeutic effectiveness on polysomnography. For patients with inadequate CPAP use, surgery should be considered.

Heart rate variability during wakefulness as a marker of obstructive sleep apnea severity

STUDY OBJECTIVES

Patients with obstructive sleep apnea (OSA) exhibit heterogeneous heart rate variability (HRV) during wakefulness and sleep. We investigated the influence of OSA severity on HRV parameters during wakefulness in a large international clinical sample.

METHODS

1247 subjects (426 without OSA and 821 patients with OSA) were enrolled from the Sleep Apnea Global Interdisciplinary Consortium. HRV parameters were calculated during a 5-minute wakefulness period with spontaneous breathing prior to the sleep study, using time-domain, frequency-domain and nonlinear methods. Differences in HRV were evaluated among groups using analysis of covariance, controlling for relevant covariates.

RESULTS

Patients with OSA showed significantly lower time-domain variations and less complexity of heartbeats compared to individuals without OSA. Those with severe OSA had remarkably reduced HRV compared to all other groups. Compared to non-OSA patients, those with severe OSA had lower HRV based on SDNN (adjusted mean: 37.4 vs. 46.2 ms; p < 0.0001), RMSSD (21.5 vs. 27.9 ms; p < 0.0001), ShanEn (1.83 vs. 2.01; p < 0.0001), and Forbword (36.7 vs. 33.0; p = 0.0001). While no differences were found in frequency-domain measures overall, among obese patients there was a shift to sympathetic dominance in severe OSA, with a higher LF/HF ratio compared to obese non-OSA patients (4.2 vs. 2.7; p = 0.009).

CONCLUSIONS

Time-domain and nonlinear HRV measures during wakefulness are associated with OSA severity, with severe patients having remarkably reduced and less complex HRV. Frequency-domain measures show a shift to sympathetic dominance only in obese OSA patients. Thus, HRV during wakefulness could provide additional information about cardiovascular physiology in OSA patients.

CLINICAL TRIAL INFORMATION

A Prospective Observational Cohort to Study the Genetics of Obstructive Sleep Apnea and Associated Co-Morbidities (German Clinical Trials Register - DKRS, DRKS00003966) https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00003966.

Predicting CPAP Use and Treatment Outcomes Using Composite Indices of Sleep Apnea Severity

STUDY OBJECTIVES

Measures of baseline sleep apnea disease burden (apnea-hypopnea index, Epworth Sleepiness Scale) predict continuous positive airway pressure (CPAP) adherence, but composite indices of sleep apnea severity (Sleep Apnea Severity Index, Modified Sleep Apnea Severity Index) may be more robust measures of disease burden. We tested the relative prognostic ability of each measure of sleep apnea disease burden to predict subsequent CPAP adherence and subjective sleep outcomes.

METHODS

Prospective cohort study at a tertiary academic sleep center. Patients (n = 323) underwent initial diagnostic polysomnography for suspected obstructive sleep apnea and 6 mo of subsequent CPAP therapy.

RESULTS

Baseline apnea-hypopnea index and both composite indices predicted adherence to CPAP therapy at 6 mo in multivariate analyses (all p ≤ 0.001). Baseline Epworth Sleepiness Scale did not predict CPAP adherence (p = 0.22). Both composite indices were statistically stronger predictors of CPAP adherence at 6 mo than apnea-hypopnea index (p < 0.001). In multivariate analyses, baseline apnea-hypopnea index (p < 0.05) and both composite indices (both p < 0.04) predicted change in Pittsburgh Sleep Quality Index, whereas only the composite indices predicted changes in Sleep Apnea Quality of Life Index (both p < 0.001). Adjustment for treatment adherence did not affect the relationship of the composite indices with change in Sleep Apnea Quality of Life Index (both p ≤ 0.005).

CONCLUSIONS

Composite indices of baseline sleep apnea severity better predict objective CPAP adherence and subjective treatment outcomes than baseline apnea-hypopnea index and baseline Epworth Sleepiness Scale.