TGFB1 and obstructive sleep apnea syndrome: In OSA patients, active TGF-β1 levels exhibited a strong relationship with mitotic index (r = 0.405, p < 0.001), Breslow index (r = 0.419, p < 0.001) and melanoma growth rate (r = 0.309, p < 0.001) (Fig. 2).