Does CPAP therapy alter urinary albumin level in adult patients with moderate to severe obstructive sleep apnea syndrome?

Urinary albumin is a marker of cardiovascular morbidity and mortality, and also it has been viewed as a marker for vascular endothelial dysfunction in both the kidneys and systemic vasculature. Lowering urinary albumin is associated with fewer cardiovascular and renal diseases. We investigated the change in urinary albumin after 1 month of continuous positive airway pressure (CPAP) therapy in obstructive sleep apnea syndrome (OSAS). Eighteen patients (four females) in the middle-age group with moderate to severe OSAS were enrolled, who received and were compliant to CPAP therapy. Patients did not have a systemic disease or use a medication that could influence urinary albumin. Blood and urine samples were obtained in the morning after polysomnography and after 1 month of CPAP therapy to measure urinary albumin excretion and urinary albumin-to-creatinine ratio. Urinary albumin excretion (UAE) and urinary albumin/creatinine ratio (UACR) decreased significantly after 1 month of CPAP therapy: UAE at baseline and 1 month, 50 (1.1-174.8) and 22.7 (4.1-55.9); UACR, 27 (18.5-51.6) and 10.6 (4.3-43.1). UAE alteration was significantly associated with proportion of sleep time spent below an SaO(2) of 90 %. Serum creatinine, serum total cholesterol, and creatinine clearance also decreased after 1 month of CPAP therapy. Albuminuria is not rare in patients with OSAS and can be corrected after CPAP therapy. Determination of urinary albumin level is a simple, inexpensive, and noninvasive method that could be a promising biomarker to identify a high-risk population in patients with OSAS who may benefit from closer medical follow-up and preventive therapy.