REN and obstructive sleep apnea syndrome: On the other hand, OSA acts as an aggravating factor for CKD by promoting sustained or resistant hypertension, intermittent nocturnal hypoxia, activation of the renin-angiotensin-aldosterone system (RAAS), and persistent oxidative stress, all of which are believed to culminate in endothelial injury, tubulointerstitial fibrosis, and progressive decline in glomerular filtration rate26,28,32.