# The correlation between reactive hyperemia index and endothelial dysfunction markers in patients with hypertension and obstructive sleep apnea syndrome: a cross-sectional study

## TL;DR

This study shows that the reactive hyperemia index (RHI) is a useful indicator of vascular endothelial dysfunction in patients with both hypertension and obstructive sleep apnea.

## Contribution

The study identifies RHI as a practical and significant marker for assessing endothelial injury in patients with co-existing hypertension and OSAHS.

## Key findings

- RHI showed strong inverse correlations with endothelial dysfunction markers like VWF, VEGF, and EMPs.
- A 1-SD increase in AHI and endothelial markers was associated with a significant decrease in RHI.
- RHI is proposed as a routine test for evaluating vascular endothelial function in these patients.

## Abstract

Currently, there is a lack of clinical studies on how to stratify endothelial dysfunction based on the severity of co-existing hypertension and OSAHS. This evidence gap hinders clinicians’ ability to accurately assess disease burden and determine the best timing and intensity of intervention for these high-risk patients. This study aimed to investigate the impact of hypertension combined with OSAHS on vascular endothelial function.

Patients aged 35–60 years with hypertension and OSAHS were consecutively recruited from the outpatient department of the Department of Cardiology at the Chengdu Pidu District People's Hospital, from July 1, 2023, to December 31, 2023. AHI, RHI and endothelial damage-related markers [Von Willebrand Factor (VWF), Vascular Endothelial Growth Factor (VEGF), and Endothelial Microparticles (EMPs)] were measured. Routine examination data were collected.

The correlation analysis between AHI, RHI, and hypertension grade and hypertension stage showed correlation coefficients less than 0.2, indicating almost no linear relationship. The correlation coefficient between AHI and RHI was −0.58 (P < 0.001). The correlation coefficients between AHI and VWF, VEGF, and EMPS were 0.56 (P < 0.001), 0.49 (P < 0.001), and 0.66 (P < 0.001). The correlation coefficients between RHI and VWF, VEGF, and EMPS were −0.62 (P < 0.001), −0.63 (P < 0.001), and −0.67 (P < 0.001). The RHI showed significant inverse associations with the studied variables.A 1-SD increase in AHI, vWF, VEGF, and EMPs was associated with a decrease in RHI of 0.02, 0.62, 0.63, and 0.67 units, respectively. (β = –0.02, adjusted β = –0.60, P < 0.01; β = –0.62, adjusted β = –0.64, P < 0.01; β = −0.63, adjusted β = –0.64, P < 0.01; β = −0.67, adjusted β = –0.71, P < 0.01).

In patients with hypertension combined with OSAHS, RHI can be used as an important indicator in routine tests of vascular endothelial function to predict the degree of vascular endothelial injury.