TNFRSF11B and obstructive sleep apnea syndrome: The study by Kosacka et al. revealed no differences in the concentrations of OPG in the serum between OSA patients and the control group and described no correlations between the concentrations of serum OPG and AHI, although there were higher serum concentrations of OPG between OSA patients with cardiovascular disease (CVD) and OSA patients without CVD [29].