Fixed but not autoadjusting positive airway pressure attenuates the time-dependent decline in glomerular filtration rate in patients with obstructive sleep apnea

BACKGROUND: The impact of treating obstructive sleep apnea (OSA) on renal function decline is controversial. Previous studies usually included small samples and did not consider specific effects of different continuous positive airway pressure (CPAP) modalities. The aim of this study was to evaluate the respective influence of fixed and auto-adjusting CPAP modes on estimated glomerular filtration rate (eGFR) in a large sample of patients derived from the prospective European Sleep Apnea Database (ESADA) cohort. METHODS: In patients of the ESADA, eGFR before and after follow-up was calculated using the CKD-EPI equation. Three study groups were investigated, namely untreated patients (n=144), patients receiving fixed continuous positive airway pressure (fCPAP) (n=1,178), and patients on auto-adjusting CPAP (APAP) (n=485). RESULTS: In the whole sample, eGFR decreased over time. The rate of eGFR decline was significantly higher in the subgroup with eGFR above median [91.42 ml/min/1.73m2] at baseline (p<0.0001 for effect of baseline eGFR). This decline was attenuated or absent (p<0.0001 for effect of treatment) in the subgroup of OSA treated by fCPAP. A follow-up duration exceeding the median (541 days), was associated with eGFR decline in the untreated and APAP groups, but not in the fCPAP group (p <0.0001 by two-way ANOVA for interaction between treatment and follow-up length). In multiple regression analysis, eGFR decline was accentuated by advanced age, female gender, cardiac failure, higher baseline eGFR and longer follow-up duration, while there was a protective effect of fCPAP. CONCLUSION: Fixed CPAP but not APAP, may prevent eGFR decline in OSA.