Study On Pathogenesis Of Hypertension In Obstructive Sleep Apnea-Hypopnea Syndrom

Objectives: Obstructive sleep apnea-hypopnea syndrom(OSAHS) is an independent risk factor for hypertension, independent of age, sex, obesity, smoking, alcohol abuse, life stress and heart or kidney disease. The study explored the role of sympathetic nerve, renin-angiotensin-aldosterone system(RAAS), endothelial dysfunction and atrial natriuretic peptide(ANP) in the pathogenesis of hypertension in OSAHS, based on comparing the level of plasma norepinephrine(NE), renin activity(PRA), angiotensin-II(ATII), aldosterone(ALD), ANP, endothelin(ET), serum nitrogen monoxid(NO) and urine vanillyl mandalic acid(VMA) in different groups. Methods: Based on polysomnography(PSG), blood pressure(BP) and disease history, ninety-three subjects were divided into four groups: OSAHS with hypertension group(OH group), OSAHS without hypertension group(O group), hypertension without OSAHS group(H group), normal control group(N group). Before sleep and in the next morning blood specimens were collected to assay the level of NE, PRA, ATII, ALD, ANP, ET, NO and urine from 22pm to 6am were collected to assay the level of VMA. At the same time BP were measured before sleep and in the next morning.Results: â‘ Patients of OH group and O group had significantly increased MAP (p<0.05), DBP(p<0.01) in the next morning compared with those before sleep and OH group had significantly increased SBP(p<0.05). Patients with OSAHS missed normal nocturnal BP rhythm. But the MAP in N group and H group in the next morning was decreased and the change of BP showed dipper. MAP in the next morning was Positively correlated with AHI, ODI₄ and T90 and negatively correlated with minSaO₂ in patients with OSAHS including hypertension and normotension. â‘¡ Patients in OH group and O group had significantly increased plasma NE value(O group: p<0.05, OH group: p<0.01) in the next morning compared with those before sleep and the change was more significant in the hypertension group compared tonormotension group(p<0.01). Compared with H group, plasma NE value in OH group before sleep had no significant difference. Plasma NE value had no significant difference in H group before sleep compared with that in the next morning. Plasma NE value in N group was lower before sleep than that in the next morning. There was not significant difference in urine VMA value of all groups before sleep compared with that in the next morning. Plasma NE value in patients with OSAHS including hypertension and normotension in the next morning was Positively correlated with MAP, AHI, ODN4, ODI4, T90 and negatively correlated with minSaO2 and MSaO2. ?Plasma PRA value before sleep in OH group and H group was higher than that other groups(p<0.05). Plasma PRA value in both H group and N group decreased in the next morning, but increased in O group and OH group especially the latter. There was no significant difference in Plasma AT II value before sleep among all groups. Plasma AT II value in the next morning increased significantly in 0 group and OH group(p<0.001) contrary to other groups. Plasma AT II value in the next morning in O group and OH group higher than N group, but had no significant difference compared with that in H group. Before sleep there was no significant difference in Plasma ALD value among four groups. In the next morning plasma ALD value in O group and N group decreased and has no significant difference in H group and OH group compared with that before sleep. In the next morning plasma ALD value in OH group was higher than that in N group. Plasma PRA, AT II value in the next morning in patients with OSAHS including hypertension and normotension was Positively correlated with MAP, AHI, maximum apnea time, total apnea time, ODN4, ODI4, T90 and negatively correlated with minSaO2 and MSaO2.The change of PRA and AT II in the next morning compared with that before sleep was Positively correlated with BP. ?There was no significant difference in Plasma ANP value before sleep and in the next morning among all group. ?Plasma ET value in both O group and OH group increased significantly in the next morning contrary to othergroups. Before sleep and in the next morning serum NO value in both O group and OH group was lower than that in N group. In the next morning serum NO value in both O group and OH group decreased significantly contrary to other groups. Plasma ET value in the next morning in patients with OSAHS including hypertension and normotension was Positively correlated with MAP, AHI, maximum apnea time, total apnea time, ODN4, ODI4, T90 and negatively correlated with minSaO2 and MSaO2. Serum NO value in the next morning in patients with OSAHS including hypertension and normotension was negatively correlated with MAP, AHI, maximum apnea time, total apnea time, ODN4, ODI4, T90 and Positively correlated with minSaO2 and MSaO2.Conclusions: ?Patients with OSAHS missed normal nocturnal BP rhythm and their BP curve show non-dipper. ?Patients with OSAHS elevate sympathetic activity. It indicated sympathetic activation has an important role in transient and sustained increasing of BP in OSAHS. (3)it is indicated that OSAHS contributes to the development of hypertension by stimulating RAAS excretion. (4)OSAHS increases the level of ET and decreases the level of NO. It suggests endothelial dysfuntion is characterized by an imbalance of endothelium-derived relaxing and contracting factors may contribute to progression of hypertension in OSAHS.