B31-10 Arousal Threshold in Patients With Obstructive Sleep Apnea Living at High Altitude

Introduction Obstructive sleep apnea (OSA) comprises several endotypes, one of which is a low arousal threshold (AT). Patients with a low AT experience premature termination of respiratory events, which prevents full restoration of pharyngeal patency. Low AT has been proposed as a treatable trait and can be clinically estimated using polysomnographic (PSG) parameters. Identifying these patients may facilitate a more personalized approach to OSA management. This study aimed to describe the prevalence and clinical correlates of low arousal threshold in a cohort of patients with OSA living in Bogotá (2640 m above sea level). Methods We conducted a retrospective cross-sectional study including adults who underwent baseline PSG at Fundación Neumológica Colombiana, with a confirmed diagnosis of OSA (apnea-hypopnea index [AHI] > 5 events/hour). Low AT was defined by the following PSG-based score: (AHI < 30 events/hour) + (nadir SpO2 > 82.5%) + (Fhypopneas > 58.3%); a score ≥ 2 indicates low AT. Qualitative variables were expressed as absolute and relative frequencies. Quantitative variables were assessed for normality (Shapiro-Wilk test) and presented as means ± SD or medians (IQR). Comparisons between groups (low vs. high AT) were made using t-tests or Wilcoxon tests for continuous variables, ANOVA or Kruskal-Wallis for multiple groups, and χ² tests for categorical variables. Statistical analyses were performed using SPSS v22.0. The study was approved by the institutional ethics committee. Results A total of 355 adults with OSA were included; 44.5% were women and the mean age was 54.6 ± 14.9 years. Most participants were non-obese (65.6%), and 50.1% had severe OSA. Low AT was identified in 47.6% of the cohort. It was more frequent among women, younger participants (<65 years), non-obese individuals, and those with less severe OSA. Table 1. In multivariate analysis, age ≤ 65 years, female sex, and BMI ≤ 30 kg/m² were independently associated with a higher likelihood of low AT.Table 2 Conclusions In this high-altitude population, nearly half of patients with OSA exhibited a low arousal threshold—higher than rates reported at sea level. Recognizing OSA endotypes, such as low AT, may guide individualized treatment strategies and improve management precision.