To analyze the relationship between obstructive sleep apnea (OSA) and nocturnal blood pressure, and to evaluate the possible effect of obesity in this association, so as to provide reference for further exploring the mechanism of OSA-related hypertension.

A total of 753 adult patients diagnosed with OSA were randomly selected from August 2021 to December 2022 in the Sleep Medicine Center of the Fourth West China Hospital of Sichuan University because of snoring, apnea, and other reasons. After polysomnography (PSG) was completed, 753 adult patients diagnosed with OSA were selected as research subjects. The general data of patients, PSG related data, nocturnal blood pressure and related indicators were collected. Correlation analysis and structural equation model were used to analyze the effects of OSA and obesity on nocturnal blood pressure.

In patients with OSA, Apnea Hyponea Index (AHI) was positively correlated with systolic blood pressure (SBP), diastolic blood pressure (DBP) (r=0.297 and 0.222, P < 0.001), and BMI (r=0.443, P < 0.001), and BMI was positively correlated with SBP and DBP (r=0.313 and 0.260, P < 0.001). The results of structural equation model suggested that obesity played an intermediary role in the effect of OSA on nocturnal SBP and DBP. The standardized intermediary effect values were 0.063 (95%CI: 0.035-0.090) and 0.059 (95%CI: 0.032-0.087), respectively, and the proportion of intermediary effect was 21.72% and 26.22%, respectively.

OSA can directly affect the blood pressure of patients. At the same time, obesity plays an intermediary role in the effect of OSA on SBP and DBP.