Hypoxic Burden from Obstructive Sleep Apnoea is Increased in Pacific Islanders with distinct Pathophysiological Traits.

STUDY OBJECTIVES: Obstructive sleep apnoea (OSA) is common in Pacific Islanders; however, its pathophysiological mechanisms are unknown. We compared OSA severity and endotypes between Pacific Islanders and Caucasians. METHODS: Retrospective polysomnography data were analysed using inverse probability of treatment weighting (IPTW) to balance age, sex, and BMI. Sleep stage endotypes were derived using validated non-invasive methods. Generalised regression models (GLMs) were used to estimate population-average differences and rank-based tests used as sensitivity analyses. RESULTS: 42 Pacific Islanders vs 62 Caucasians were included. There was no difference in apnoea-hypopnoea index between groups (adjusted mean difference 2.8 events/h, 95% CI [-9.0 to 14.5]; p= 0.64). Pacific Islanders had higher mean apnoea length (5.6 s, [2.1 to 8.9]; p= 0.001), oxygen desaturation index ≥ 3% (12.5 events/h, [4.3 to 20.7]; p = 0.003), average desaturation during events (2.4%, [1.1 to 4.0]; p <0.001), time with SpO₂ <90% (12.3 min, [2.5 to 22.0]; p= 0.016), hypoxic burden (67.4 %·min/h, [21.7 to 113.2]; p= 0.012) and supine proportion (20.8% [6.6 to 34.9], pGLM = 0.005). They also had higher REM arousal threshold (14.4 %Veupnoea, [1.3 to 27.5]; p= 0.033), lower REM Vpassive (-13.3 %Veupnoea, [-23.8 to -2.9]; p= 0.015), and higher NREM loop gain (0.04, [0.00 to 0.09]; p= 0.047, except for REM arousal threshold endotype differences were absent after supine adjustment. CONCLUSIONS: In Pacific Islanders, OSA is characterised by longer apnoea and increased hypoxic burden, with distinct endotypes. Strategies targeting endotypes and hypoxic burden may improve treatment and mitigate cardiometabolic consequences in this population.