Interrelationship among Obstructive Sleep Apnea,Renal Function and Survival: A Cohort Study

Previous studies showed a bidirectional relationship between renal function decline and obstructive sleep apnea (OSA) syndrome. Continuous Positive Airway Pressure (C-PAP) treatment was shown to preserve the kidney function in OSA patients. This study aims to investigate the progression of long-term renal function in OSA patients treated with different PAP strategies (patients were divided into two groups, fixed C-PAP or other PAP-automatic and bilevel pressure). Comorbidities and 10-years survival were also evaluated. We performed a retrospective, observational, single-center, cohort study, including the first 40 consecutive patients enrolled from 2009 in the Respiratory disease Unit at the Vercelli University Hospital database. The patient inclusion criteria were: age ≥ 18 years with OSA syndrome according to AASM (American Academy of Sleep Medicine) guidelines. Creatinine serum levels (mg/dL) and the estimated Glomerular Filtration Rate (eGFR, mL/min calculated by CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration equation)) were measured at 3 different time points: at baseline, 3 years and 8 years after PAP treatment. The Kaplan-Meier survival curves stratified according to PAP treatment and compliance have been reported together with log-rank test estimation. In our study, we found a significant creatinine serum level reduction after 3 years of fixed C-PAP treatment (p value = 0.006) when compared to baseline values. However, we observed that the long-term C-PAP benefit was not significant (p value = 0.060). Our data confirmed the progressive renal function decline in OSA patients, especially in those using other-PAP treatments; nevertheless, OSA treatment with a fixed C-PAP device has shown, in the short term, a significant improvement in renal function. By contrast, in our study, long-term benefits after 8 years are not been demonstrated probably because of the lack of compliance of the patients and the aging effect.