RNLS and obstructive sleep apnea syndrome: Furthermore, renalase concentration was statistically significantly lower in the group with moderate-to-severe OSA (AHI ≥ 15) compared with the group with mild-to-no OSA (AHI < 15) (139.56 ± 175.72 ng/ml vs. 221.76 ± 233.23 ng/ml, p = 0.044).