The physiological phenotype of obstructive sleep apnea differs between Caucasian and Chinese patients

Study Objectives: The mechanisms responsible for the development of obstructive sleep apnea (phenotypic "traits") are known to differ between individuals and may differ across ethnicities. We aimed to examine whether loop gain, arousal threshold, pharyngeal collapsibility and muscle compensation differ between Chinese and Caucasian individuals with OSA. Methods: We noninvasively determined the relative contribution of loop gain, arousal threshold, pharyngeal collapsibility, and muscle compensation from the ventilatory flow pattern recorded during a standard clinical polysomnography in a cohort of age and AHI matched Caucasian and Chinese patients with moderatesevere OSA (n = 90). Results: Chinese participants had significantly more collapsible pharyngeal airways as indicated by a lower V-passive (68.9 [51.5-75.2] vs. 74.0 [65.1-80.4] %V-eupnea, U = 703, p = 0.012), but less ventilatory control instability as indicated by a lower loop gain (0.60 [0.50-0.67] vs. 0.63 [0.57-0.81], U = 762, p = 0.043) compared with Caucasian participants. Further, multiple logistic regression analyses demonstrated that the combined pharyngeal collapsibility (V-passive) and loop gain traits help to better explain the differences between the groups beyond upper-airway collapsibility alone. No statistically significant group differences were found in muscle compensation or arousal threshold traits between groups. Conclusion: Individuals of Chinese descent appear to have OSA that is driven much more by the relative contribution of their anatomical predisposition and to a lesser extent nonanatomical causes compared with Caucasians. Future research should focus on determining if Chinese versus Caucasian ethnicity is an important contributing factor to clinical outcomes and therapeutic responses in OSA.