Fulsen B - Patients with obstructive sleep apnea syndrome (OSAS) were examined to determine the correlation of serum levels of gamma glutamyl transferase (GGT), which represents a novel marker in the prediction of cardiovascular risk, with hypertension and the degree of the upper airway obstruction in these subjects. High serum levels of GGT were found to be strongly correlated with concomitant hypertension in this population. As per observations, this biomarker may be helpful in grading the severity of obstructive sleep apnea and correlated with hypertension.