highly significantp < 0.001
The results of univariable Cox regression with RCS showed the HR was approximately close to one until 1.3 of VR and a highly significant positive correlation between VR and HR was presented from the onset of 1.3 of VR (HR = 1.05 per 0.1 increase, 95% CI [1.04–1.07], p < 0.001) (Fig. 2 c).