Gamma-glutamyl transferase activity as a predictive marker for severity of obstructive sleep apnea syndrome and concomitant hypertension

BackgroundChronic intermittent hypia, inflammation and oxidative stress are involved in resultant obstructive sleep apnea syndrome (OSAS), which may affect numerous regulatory mechanisms that play a role in the regulation of blood pressure. Gamma-glutamyl transferase (GGT) is a novel marker in the prediction of cardiovascular risk. ObjectiveThe objective of this study was to investigate the correlation of serum levels of GGT with hypertension and the degree of the upper airway obstruction in subjects with OSAS. MethodsA total of 270 subjects that met the inclusion criteria were enrolled in the study. The subjects were divided into four separate groups according to the apnea-hypopnea index (AHI) scores as the control group (AHI<5), mild OSAS group (AHI 5-15), moderate OSAS group (AHI 16-30) and severe OSAS group (AHI >30). A further classification of the OSAS subjects was made in two groups based on the presence of hypertension. ResultsThe study included 43 control individuals and 59 subjects with mild, 54 subjects with moderate and 114 subjects with severe OSAS. The serum levels of GGT were found to be significantly correlated with OSAS severity (control group: 183.3, mild OSAS: 23.6 +/- 7.3, moderate OSAS: 26.4 +/- 7.5 and severe OSAS: 39.8 +/- 12). Serum levels of GGT were found to be significantly higher in OSAS subjects with concomitant hypertension than in the group without associated hypertension (P<.05). The results showed that the adjusted mean GGT under OSA without hypertension (M-adj=28.76, SE=0.71) was significantly lower than in cases with OSA with hypertension (M-adj=42.79, SE=1.19). ConclusionThe present study indicated a strong correlation between high serum levels of GGT and concomitant hypertension in subjects with obstructive sleep apnea. This biomarker may be helpful in grading the severity of obstructive sleep apnea and correlated with hypertension in this population.