Potential Effect Of Obstructive Sleep Apnea Severity On Screening For Primary Aldosteronism

Objective Primary aldosteronism(PA)and obstructive sleep apnea(OSA)are the two most forms of secondary hypertension,both of which are highly associated with renin-angiotensin-aldosterone system(RAAS).Previous studies have shown that OSA can increase plasma renin activity by activating sympathetic nervous system and renin-angiotensin-aldosterone system through repeated hypoxia and airway collapse.PA is endocrine hypertension characterized by aldosterone autonomous hypersecretion and feedback inhibition of renin activity.Therefore,we hypothesize that activation of RAAS in OSA may affect the cut-off value of aldosterone to renin ratio(ARR)in screening PA patients.The present study aimed to examine the impact of obstructive sleep apnea severity on screening for primary aldosteronism patients.Methods 336 hypertensive inpatients with snore admitted to the Hypertension Center of People's Hospital of Xinjiang Uygur Autonomous Region from October 2008 to December 2010were selected.All of these patients performed polysomnography(PSG).According to apnea hypopnea index(AHI),the patients were divided into non-OSA(AHI<5 events/hour),mild OSA(5?AHI<15 events/hour),moderate OSA(15?AHI<30 events/hour),and severe OSA(AHI?30events/hour).In addition to seated plasma aldosterone concentration(PAC)and plasma renin activity(PRA)measured in all patients and saline infusion test(SIT)were further performed.Patients with ARR>15(ng/dl)/(ng/ml/h)were diagnosed as PA according to plasma aldosterone concentration(PAC)>10 ng/dl and plasma renin activity(PRA)<0.65ng/ml/h after SIT.Results The preponderance of males was 250(74.4%)in the 336 patients,whose mean age was 44±8 years and body mass index(BMI)was 27.9±3.7 Kg/m~2.The mean office blood pressure was 141±20/97±13 mmHg and duration of hypertension was 2(0.6,6.0)years.The serum potassium was 3.87±0.34 mmol/l and hypokalemia accounted for 20.8%.On the basis of PSG findings,the AHI was 12.9(4.7,28.2)events/h.The median PRA was 0.79(0.38,1.84)ng/(ml/h)and PAC was 12.42(9.58,16.92)ng/dl.The corresponding median ARR was14.4(7.4,33.3)(ng/dL)/(ng/mL/h).The detection rate of PA in the total population was 9.2%.In the subgroup analysis of clinical data,the analysis of the factors that might affect the screening for PA showed that the ARR of PA was not significantly affected by the obesity,hypokalemia and the lowest blood oxygen saturation.The results of spearman correlation analysis between AHI and PRA,PAC,ARR in all OSA patients showed that there was a positive correlation between AHI and PRA(r=0.156,P=0.013),a negative correlation between AHI and ARR(r=-0.147,P=0.020)and no significant correlation between AHI and ARR(r=0.059,P=0.350).In exploring the effect of OSA severity on the ARR cutoff value screening for PA,the optimal cutoff value of ARR for PA in moderate OSA patients was 18.0(ng/dl)/(ng/ml/h),resulting in a sensitivity of 100%(79.4-100.0%),specificity of 68.79%(60.5-76.3%),positive-predictive value of 26.7%(16.1-39.7%),negative-predictive value of100%(95.9-100%)and AUC of 0.866.Meanwhile,for primary aldosteronism patients with non&mild-OSA,when the optimal cutoff value of ARR was 27.0(ng/dl)/(ng/ml/h),resulting in a sensitivity of 93.33%(68.1-99.8%),specificity of 70.12%(62.5-77.0%),positive-predictive value of 22.2%(12.7-34.5%),negative-predictive value of 99.1%(95.3-100.0%)and AUC of 0.882.Conclusions 1.A positive correlation between AHI and PRA and a negative correlation between AHI and ARR in OSA patients.2.When the ARR of moderate and severe OSA patients do not meet the screening criteria,it is necessary to comprehensively judge the clinical characteristics in order to avoid the missed diagnosis of PA.3.Screening for PA in patients with hypertension complicated with OSA may require a moderate reduction of the ARR cut-off point,which needs to be further verified in more OSA populations.