Hypoxic Burden Based on Automatically Identified Desaturations Is Associated with Adverse Health Outcomes.

Abstract

Recent studies have shown that sleep apnea-specific intermittent hypoxemia, quantified by the hypoxic burden (HB), predicted cardiovascular disease (CVD) -related mortality in community-based and clinical cohorts. Calculation of HB is based on manual scoring of hypopneas and apneas, which is time consuming and prone to inter-scorer variability. To validate a novel method to quantify the HB that is based on automatically-scored desaturations. The sample included 5655 middle-aged or older adults from the Sleep Heart Health Study (SHHS) (52.8% women; age 63.2 ± 11.3 years). The original HB method was based on a subject-specific search window, obtained from ensemble average of SpO2 signals, synchronized with respect to the termination of scored respiratory events. In this study, however, the search window was obtained from ensemble average of SpO2 signals which synchronized with respect to the minimum of all automatically identified desaturations (≥ 2%, and other thresholds including 3% and 4% in sensitivity analyses). The time interval between the two maxima around the minimum saturation was defined as the search window. The oximetry-derived hypoxic burden (HBOxi) was defined as the total area under all desaturation curves (restricted by the search window) divided by the total sleep time. Logistic and Cox regression models assessed the adjusted odds ratio (aOR)/hazard ratio (aHR) of Excessive Daytime Sleepiness (EDS), hypertension (HTN), and CVD mortality per 1 standard deviation increase in HBOxi, after adjusting for several covariates and confounders. The Spearman's rank correlation between HB (median [IQR]= 34.4[18.4 - 59.8] %min/h) and HBOxi (median [IQR]= 34.5[21.6-53.8] %min/h) was 0.81 (p<0.001). Similar to HB, HBOxi was significantly associated with EDS (aOR [95% CI]: 1.17 [1.09 - 1.26]; per 1SD), HTN (aOR [95% CI]: 1.13[1.05 - 1.21]), and CVD mortality (aHR [95% CI]: 1.15 [1.01 - 1.30]) in fully-adjusted models. The oximetry-derived hypoxic burden was highly correlated with the hypoxic burden based on manually scored apneas and hypopneas and was associated with EDS, HTN, and CVD mortality with similar effect sizes as previously reported. This method could be incorporated into wearable technology that accurately records oxygen saturation signals.