Objectives: Evaluate the effect of CPAP to reduce the progression of chronic kidney disease or CKD (the decline of glomerular filtration rate is ≥ 30%) in patients with early-stage renal disease and sleep apnea syndrome (OSAS). Other objectives are; determine the prevalence of OSAS in patients with early-stage renal disease and evaluate the changes in inflamatories markers and endothelial damage, the state of KDIGO, cardiovascular events, mortality and cost-effectiveness analysis in CPAP group versus non-CPAP group patients.