SP724SLEEP DISORDERED BREATHING (SDB) REEMERGENCE AND SYSTEMIC HYPERTENSION IN RENAL TRANSPLANT PATIENTS: A LONGITUDINAL STUDY

Abstract

INTRODUCTION: Hypertension is common in sleep disordered breathing (SDB) and nocturnal hypertension -a hallmark of this disorder-has a 74% prevalence in renal transplant patients. SDB is frequent in dialysis patients and it reduces in the early months post-transplantation to gradually increase thereafter and blood pressure follows the same pattern in this population. Studying the longitudinal evolution of state of art polymonographic biomarkers of SA [the apnea hypopnea index, AHI; minimum O2 saturation (%), Min-O2 (%)] and blood pressure (24 h ambulatory BP monitoring, 24h ABPM) may provide important information on the role of the reemergence of SDB in hypertension in transplant patients. METHODS: We recorded 24h ABPM and performed polysomnography studies to measure the AHI and Min-O2 in a series of 221 clinically stable transplant patients (age: 46.9±11 years; M: 70.1%). Overall, 404 recordings over a follow up extended up to 110 months (median 52.1 months; IQR: 36.8-67.3 ) were performed. Longitudinal data analysis was performed by Linear Mixed Models (LMM). RESULTS: At baseline 24h systolic BP (P=0.03) as well as night time systolic BP (P=0.01) associated with the severity of SDB as assessed by the apnea hypopnea index (AHI). On longitudinal analysis the AHI was strongly associated with 24h ABPM and BP during night time was the closest correlate of this parameter. Indeed in an analysis adjusted for age, gender, smoking, diabetes, cholesterol, BMI, background CV comorbidities, phosphate, Hb, eGFR, albumin, one unit increase in the AHI entailed a 0.14 mmHg in 24h systolic ABPM (P=0.027) and a 0.20 mmHg increase in nocturnal BP (P=0.002). Diastolic BP was unrelated with the AHI. Oxygen desaturation during night time correlated both with nocturnal changes in systolic and diastolic BP more closely than the AHI. Indeed in fully adjusted analyses a 1%decline in Min-O2 associated with a 0.24 mmHg rise in night time systolic BP (P=0.006) and a 0.19 mmHg rise in diastolic BP (P=0.007). CONCLUSIONS: In stable renal transplant patients, the severity of SDB is a functional correlate of systemic hypertension as assessed by 24hABPM and such a link is most consistent during night-time. Furthermore, the SDB severity-nocturnal hypertension relationship is much stronger in longitudinal analyses extended up to 110 months than in cross sectional analyses. Correcting risk factors for SDB and treating this disorder may improve hypertension control and clinical outcomes in renal transplant patients.