Editorials

Polysomnography in the Diagnosis of the Obstructive Sleep Apnea-Hypopnea Syndrome: Where Do We Draw the Line?

Emerging evidence witnesses the association of air pollution exposure with sleep disorders or the risk of obstructive sleep apnea (OSA); however, the results are not consistent. OSA patients with or without a low arousal threshold (LAT) have different pathology and therapeutic schemes. No study has evaluated the potential diverse effects of air pollution on the phenotypes of OSA. The current study aimed to evaluate the associations of short-term and long-term exposure to air pollution with sleep-disordered measures and OSA phenotypes. This cross-sectional study consisted of 4634 participants from a sleep center in Taipei from January 2015 to April 2019. The personal exposure to ambient PM_2.5 and NO₂ was assessed by a spatial-temporal model. Overnight polysomnography was used to measure the sleep parameters. According to a developed clinical tool, we defined the low arousal threshold (LAT) and identified the OSA patients with or without LAT. We applied a generalized linear model and multinomial logistic regression model to estimate the change of sleep measures and risk of the OSA phenotypes, respectively, associated with an interquartile range (IQR) increment of personal pollution exposure after adjusting for the essential confounders. In the single-pollutant model, we observed the associations of NO₂ with sleep-disordered measures by decreasing the total sleep time, sleep efficiency, extending the time of wake after sleep onset, and the association of NO₂ with the increased risk of LAT OSA by around 15%. The two-pollutant model with both long-term and short-term exposures confirmed the most robust associations of long-term NO₂ exposure with sleep measures. An IQR increment of NO₂ averaged over the past year (6.0 ppb) decreased 3.32 min of total sleep time and 0.85% of sleep efficiency. Mitigating exposure to air pollution may improve sleep quality and reduce the risk of LAT OSA.

Strong evidence exists for clinically relevant night-to-night variability of respiratory events in patients with suspected OSA.

How many sleep study nights are required to diagnose OSA accurately?

Patients with suspected OSA underwent up to 14 nights of pulse oximetry (PO) at home and one night of in-hospital respiratory polygraphy (RP). The accuracy of each of the 13 sleep study nights was analyzed using the mean oxygen desaturation index 3% (ODI_3%) of all 14 nights as a reference. Multiple regression analyses assessed possible predictors for night-to-night variability.

One hundred three patients underwent in-hospital RP. Using only the results of the RP, 19.7% were misdiagnosed using an ODI_3% cutoff of 15/h. One hundred eight patients underwent properly performed PO studies at home with a coefficient of variation (CV) of 31.5% (SD, 14.7%) across all nights. The first PO night demonstrated a sensitivity of 71.4% (95% CI, 55.4%-84.3%) and a specificity of 89.4% (95% CI, 79.4%-95.6%) to diagnose moderate OSA. Using only the first PO night, the negative predictive value was 83.1%. Adding a second recording night increased sensitivity up to 88.1% (95% CI, 74.4%-96.0%) with a slightly lower specificity of 85.9% (95% CI, 74.9%-93.4%). The ODI_3% of the in-hospital RP showed an independent negative association to the log-transformed CV (exponentiated coefficient, 0.989; 95% CI, 0.984-0.995).

One single night of in-hospital RP may miss relevant OSA. Multiple study nights, for example, using ambulatory oxygen saturation monitoring, increase accuracy for diagnosing moderate OSA.

ClinicalTrials.gov; No.: NCT03819361; URL: www.clinicaltrials.gov

Portable monitoring is a convenient means for diagnosing sleep apnea. However, data on whether one night of monitoring is sufficiently precise for the diagnosis of sleep apnea are limited.

The current study sought to determine the variability and misclassification in disease severity over three consecutive nights in a large sample of patients referred for sleep apnea.

A sample of 10,340 adults referred for sleep apnea testing was assessed. A self-applied type III monitor was used for three consecutive nights. The apnea-hypopnea index (AHI) was determined for each night, and a reference AHI was computed by using data from all 3 nights. Pairwise correlations and the proportion misclassified regarding disease severity were computed for each of the three AHI values against the reference AHI.

Strong correlations were observed between the AHI from each of the 3 nights (r = 0.87-0.89). However, substantial within-patient variability in the AHI and significant misclassification in sleep apnea severity were observed based on any 1 night of monitoring. Approximately 93% of the patients with a normal study on the first night and 87% of those with severe sleep apnea on the first night were correctly classified compared with the reference derived from all three nights. However, approximately 20% of the patients with mild and moderate sleep apnea on the first night were misdiagnosed either as not having sleep apnea or as having mild disease, respectively.

In patients with mild to moderate sleep apnea, one night of portable testing can lead to misclassification of disease severity given the substantial night-to-night variability in the AHI.

L’échelle de somnolence d’Epworth (ESS) est un autoquestionnaire conçu en langue anglaise et utilisé dans l’évaluation de la somnolence diurne. L’objectif de cette étude est de développer une version arabe de l’ESS (AESS) et d’en évaluer la fiabilité et la validité.

L’AESS a été créée selon les recommandations de l’ISPOR Task Force for Translation and Cultural Adaptation chez des individus bilingues. Elle a été appliquée sur 91 malades référés à trois centres du sommeil libanais pour suspicion de pathologies respiratoires liées au sommeil, et sur 166 témoins en bonne santé. Les scores AESS de 60 malades ont été comparés à ceux de 60 témoins appariés selon l’âge, le sexe et l’indice de masse corporelle. La reproductibilité a été testée chez 30 témoins. La réponse au traitement a été testée chez 15 malades après un mois de traitement par pression positive continue (PPC).

L’analyse en composantes principales a montré la convergence vers un seul facteur latent. L’AESS avait une bonne consistance interne (alpha de Cronbach 0,762, coefficient de corrélation intraclasse 0,851 [IC95 % : 0,760–0,918], Spearman 0,973, p < 0,001). L’accroissement de la sévérité du syndrome d’apnées du sommeil s’accompagne d’une augmentation du score d’AESS (p < 0,001). Le score AESS s’améliore significativement par rapport à l’état de base après PPC.

L’AESS, instrument fiable et valide pour l’évaluation de la somnolence diurne, est un outil précieux pour la pratique clinique et la recherche multicentrique.

The Epworth Sleepiness Scale (ESS) is a self-completion questionnaire developed in the English language and used for the evaluation of sleepiness. The objective of this study was to develop an Arabic version of ESS (AESS) and to investigate its reliability and the validity.

The AESS was created according to the recommendations of the ISPOR Task Force for Translation and Cultural Adaptation with bilingual individuals. It was applied to 91 patients referred to three sleep Lebanese centers for suspicion of sleep-related breathing diseases, and to 166 controls in good health. AESS scores of 60 patients were compared to 60 matched controls according to their age, sex and body mass index. Reproducibility was tested in 30 controls. The treatment response was tested among 15 patients after one month of CPAP treatment.

Principal component analysis showed convergence towards only one latent factor. The AESS had a good internal consistency (Cronbach's alpha 0.76, intraclass correlation coefficient of 0.85 (IC95%: 0.76–0.92), Spearman 0.97, P < 0.001). An increase in the severity of sleep apnea was accompanied by an increase in the score on the AESS (P < 0.001). AESS scores improved significantly after CPAP.

The AESS, a reliable and valid instrument for the evaluation of daytime sleepiness, is a valuable tool for clinical practice and multicenter research.

To evaluate the frequency of pulmonary function and sleep-breathing disorders in severely obese children and to search for their association with obesity phenotypes.

Sleep studies and spirometry were performed for 54 severely obese children.

Upper airway resistances (RAWs) were increased with RAW>200% and forced 25 s expiratory volume<80% in 83% and 60% of individuals, respectively. A decrease in functional residual capacity (FRC)<80% was found in 43%. Fifty-two percent of the children had a desaturation index>10 during sleep, and 41% of children presented at least one of three severity criteria (snoring index>300 per hour, respiratory events index (REI)>10 and arousal index>10). Univariate analyses showed a positive correlation between snoring index and BMI Z-score and neck/height ratio ($P=0.01$ and $0.04$, respectively) as between REI and the same parameters ($P=0.01$ and $0.03$, respectively). In a multivariate model with BMI Z-score, NHR still correlated with the snoring index ($P=0.02$) and REI ($P=0.01$).

In our cohort, obese children showed frequent pulmonary function and sleep-breathing disorders. The later were associated with impaired upper airway respiratory conductance.