Independent Risk Factors and Associated Comorbid Conditions Affecting Intermittent Hypoxia in 569 Patients Diagnosed with OSA

Background/Objectives: Obstructive sleep apnea (OSA) is characterized by recurrent episodes of complete or partial upper airway collapse during sleep, leading to apnea or hypopnea and recurrent oxygen desaturation. Intermittent hypoxia (IH) and sleep fragmentation have been proposed as key mechanisms contributing to the adverse cardiovascular consequences observed in OSA. The present study aimed to identify clinical variables independently associated with IH in patients with OSA and to examine their relationships with common comorbid conditions. Methods: This retrospective study included 569 adult patients diagnosed with obstructive sleep apnea (OSA) by overnight polysomnography (apnea–hypopnea index AHI ≥ 5 events/hour) between February 2020 and January 2025 at the Sleep Laboratory of Trakya University Hospital. Demographic characteristics, body mass index (BMI), AHI values, comorbid medical conditions, average nocturnal oxygen saturation, and the duration of intermittent hypoxia (time below 90% SpO2 T90) were retrieved from the laboratory database. Normality of distribution was assessed using the Kolmogorov–Smirnov test. Group differences were evaluated using the Mann–Whitney U test and the Kruskal–Wallis test with Dunn–Bonferroni post hoc analysis. Correlations were examined using Spearman’s correlation analysis, and variables independently associated with average nocturnal oxygen saturation and intermittent T90 were assessed using multivariable linear regression analysis. Results: The presence of hypertension, diabetes mellitus, and comorbid conditions was associated with significant differences in T90 among patients with OSA. T90 also differed significantly across AHI severity grades. Significant negative correlations were observed between nocturnal oxygen saturation and BMI, hypertension, diabetes, comorbidities, and age. Nocturnal oxygen saturation values likewise differed significantly across BMI-defined obesity groups. In the multivariable regression analysis, BMI, AHI, and age were independently associated with lower nocturnal oxygen saturation and longer T90. Conclusions: This study provides important insight into the complex relationships among OSA severity, patient demographics, comorbidities, and intermittent hypoxia. In multivariable analysis, BMI, AHI, and age showed independent associations with reduced nocturnal oxygen saturation and prolonged T90. These findings highlight the importance of a multidimensional clinical assessment in OSA and support the use of intermittent hypoxia metrics as additional indicators of disease burden and potential clinical impact.