FP771
A LONGITUDINAL, LONG TERM, ANALYSIS OF SLEEP DISORDERED BREATHING IN RENAL TRANSPLANT PATIENTS

INTRODUCTION: Sleep Disordered Breathing (SDB) is frequent in stage 5 Chronic Kidney Disease (CKD) and in dialysis patients. Studies in small series of dialysis patients show that SDB ameliorates in the early months after renal transplantation (Blood Purif 2008;26:485–490; ) but the long term longitudinal evolution of SDB in renal transplant patients has not been studied.

METHODS: We investigated the long term evolution of polysomnographic recordings in a cohort of 221 renal transplant patients (age: 46.9±11 years; M: 70.1%). Overall, 404 polysomnographic recordings over a follow up extended up to 110 months (median 52.1; IQR: 36.8-67.3 months) were performed. Longitudinal data analysis was performed by Generalized Estimating Equations (GEE).

RESULTS: At baseline, the median value of the apnoea-hypopnea index (AHI) was 1.8 episodes/h [interquartile range (IQR): 0.6-5.0]. One-hundred and sixty-six patients (75%) had a normal AHI (<5). Thirty-seven patients (17%) had mild to moderate SDB (AHI 5 to 14.9) and the remaining 18 patients (8%) had a severe SDB (AHI >15). AHI was directly related with age (rho=0.24, P<0.001), BMI (rho=0.27, P<0.001), serum fibrinogen (rho=0.16, P=0.027) and glucose (rho=0.14, P=0.035). Episodes of central apnea (n=173 patients, median: 0.70 episodes/h, IQR: 0.30-1.70) were more frequent than episodes of airways obstruction (n=79 patients, median: 0.40, IQR: 0.20-2.10). The median values of minimum (MinSaO2) and the average nocturnal O2 saturation were 89% and 95.6%. On longitudinal observation, the median AHI rose from 1.8 (IQR: 0.6-5.0) at baseline to 2.9 (IQR: 1.0-6.6) and to 3.6 (IQR: 1.7-10.4) at the second and the third longitudinal visit, respectively (P for trend=0.009). MinSaO2 significantly worsened over time (1st visit, 87.7±6.7%; 2nd visit, 87.2±7.5%; 3rd visit, 84.8±10.8%, P=0.048). Central apnoea episodes tended to worsen over time (P=0.057). In multiple GEE models, BMI (P<0.001) and C-reactive protein (P=0.001) emerged as the sole independent longitudinal correlates of AHI and MinSaO2 respectively while male gender associated with MinSaO2 (P=0.03) but not with the AHI.

CONCLUSIONS: SDB in renal transplanted patients shows a gradual, linear worsening over a longitudinal observation extended up to 110 months. The rise in BMI, a potentially modifiable risk factor, is an important factor underlying the risk for SDB worsening in transplant patients. Inflammation, an established consequence of overweight and obesity, goes along with SDB worsening in renal transplant patients.