Study of Renal Impairment in Patients with Obstructive Sleep Apnea Syndrome and Its Relation to the Disease Severity

Background: Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder associated with systemic complications, including renal impairment resulting from intermittent hypoxia and sympathetic activity. This study aimed to evaluate renal dysfunction in cases with OSA, investigate its correlation with disease severity, and assess the impact of continuous positive airway pressure (CPAP) therapy on kidney function. Methods: In this prospective cohort study, 100 participants (80 OSA cases and 20 healthy controls) were enrolled from Benha University Hospital (December 2022 and December 2024). All participants underwent comprehensive clinical evaluation, overnight polysomnography (PSG), renal function testing [serum creatinine, blood urea, estimated glomerular filtration rate (eGFR), urinary albumin-to-creatinine ratio (UACR)], and renal ultrasonography. OSA cases with moderate-to-severe disease received CPAP therapy for three months, followed by repeat renal evaluation. Results: The apnea–hypopnea index correlated positively with creatinine (r = 0.483), urea (r = 0.339), and UACR (r = 0.615), and negatively with eGFR (r = –0.387) (P < 0.001). After 3 months of CPAP, mean creatinine decreased from 2.01 ± 0.89 to 1.45 ± 0.64 mgper dL, and eGFR increased from 40 ± 22.88 to 56.51 ± 32.53 mLper minper 1.73 m² (P < 0.001). Compared with controls, OSA patients had greater neck circumference, higher STOP-BANG and Epworth Sleepiness Scale scores, higher AHI and oxygen desaturation index (ODI), lower mean oxygen saturation, and worse renal indices. Conclusion: OSA severity is strongly associated with renal dysfunction. CPAP therapy leads to significant improvement in kidney function, highlighting its potential renoprotective role in OSA management.