In the study of Kato et al. [20] that included 267 patients, Cyst C levels were correlated with age (r = 0.37, p < 0.001), BMI (r = 0.12, p = 0.045), AHI (r = 0.17, p = 0.007), CRP (r = 0.12, p = 0.045), and brachial-ankle pulse wave velocity (r = 0.18, p = 0.003), while severe OSAS was an independent variable for the highest quartiles of serum Cyst C levels (OR: 2.04, 95% CI: 1.04–4.01, p = 0.04) after adjustment for age, BMI, hypertension, and diabetes mellitus. Here, CRP is linked to diabetes mellitus.