O056 OSA in Pacific islanders: distinct endotypes and increased hypoxic burden

Introduction Obstructive sleep apnoea (OSA) is more prevalent in Pacific Islanders (PI); however, the pathophysiological mechanisms are unknown. We compared OSA endotypes of PI with Caucasians (C) in a sleep clinic population. Methods PI were identified from a sleep clinic database, and age, BMI, and gender matched C identified. All polysomnography records were re-scored by a single technician, and apnoea-hypopnoea index (AHI), oxygen desaturation index (ODI-3%), and average apnoea length (AAL) measured. Non-invasive estimates of pharyngeal collapsibility (Vpassive), muscle compensation (Vactive), arousal threshold (AT), loop gain (LG) and hypoxic burden (HB) were quantified. Group comparisons were conducted using inverse probability of treatment weighting to adjust for residual imbalance in age, BMI, and gender. Results 104 patients (42 PI) were included. While AHI was not different (PI: 42.2 [21.4–67.0]; C: 41.9 [17.2–82.3], events/hr; median [IQR];p=.45), AAL was longer (21– [16–26] vs 17 [14–21] seconds, p=.002), ODI-3% higher (25.3 [8.1-42.5] vs 6.7 [2.0–30.6] events/hr, p=.001) and HB greater (105.0 [45.0–231.1] vs 50.4 [17.7–124.2] %min/h, p=.005) in PI compared to C. There were no differences in Vpassive (70.8 [42.2-80.1] vs 75.7 [55.5-81.6], %Veupnea, p=.25) or Vactive (90.4 [6.3-103.2] vs 98.5 [61.2-105.0], %Veupnea, p=.26). AT was significantly higher in PI (164.5 [150.7–199.5] vs 153.1 [137.2–185.7], %Veupnea, p=.023) as was LG (0.44 [0.35-0.54] vs 0.35 [0.30–0.44], p=.041). Discussion Compared with age, gender, and BMI-balanced C, PI have prolonged apnoea, greater oxygen desaturation, and increased HB, likely due to differences in non-anatomical endotypes.