Methods: A prospective, multicentric, randomized and controlled study will be carried out for 3 years. Early-stage renal disease (G1-3 KDIGO) and OSAS patients will be included. The investigators will make a respiratory polygraphy to determinate OSAS (AHI ≥15/h) and after that, the investigators randomized patients in 2 groups; CPAP group and control group (non-CPAP treatment). Patients with AHI <15/h (non-OSAS) will be the reference group and the half of these patients, randomly chosen, will be followed up at the end of the follow up.