Sleep-Disordered Breathing and 24-Hour Ambulatory Blood Pressure Monitoring in Renal Transplant Patients: Longitudinal Study

BACKGROUND: Sleep--disordered breathing (SDB) is considered a strong risk factor for hypertension in the general population. This disturbance is common in end--stage kidney disease patients on long--term hemodialysis and improves early on after renal transplantation. Whether SDB may be a risk factor for hypertension in renal transplant patients is unclear. METHODS AND RESULTS: We investigated the long--term evolution of simultaneous polysomnographic and 24--hour ambulatory blood pressure (BP) monitoring recordings in a cohort of 221 renal transplant patients. Overall, 404 paired recordings were made over a median follow--up of 35 months. A longitudinal data analysis was performed by the mixed linear model. The apnea--hypopnea index increased from a median baseline value of 1.8 ( interquartile range, 0.6-5.0) to a median final value of 3.6 (interquartile range, 1.7-10.4; P= 0.009). Repeated categorical measurements of the apnea--hypopnea index were directly associated with simultaneous 24--hour, daytime, and nighttime systolic ambulatory BP monitoring (adjusted analyses; P ranging from 0.002-0.01). In a sensitivity analysis restricted to 139 patients with at least 2 visits, 24--hour, daytime, and nighttime systolic BP significantly increased across visits (P<0.05) in patients with worsening SDB (n= 40), whereas the same BP metrics did not change in patients (n=99) with stable apnea--hypopnea index. CONCLUSIONS: In renal transplant patients, worsening SDB associates with a parallel increase in average 24--hour, daytime, and nighttime systolic BP. These data are compatible with the hypothesis that the link between SDB and hypertension is causal in nature. Clinical trials are, however, needed to definitively test this hypothesis.