Proteinuria in obstructive sleep apnea

Background. Previous studies have reported an association between obstructi ve sleep apnea (OSA) and proteinuria, but are limited in their ability to a ssess proteinuria accurately, to adjust for confounders such as obesity, or to exclude confidently underlying renal disease in patients with OSA and n ephrotic-range proteinuria. Methods. The spot urine protein/creatinine ratio was measured in a prospect ive consecutive series of 148 patients referred for polysomnography who wer e not diabetic and had not been treated previously for OSA. The urine prote in/creatinine ratio was compared across four levels of OSA severity, based on the frequency of apneas and hypopneas per hour: <5 (absent). 5 to 14.9 ( mild). 15 to 29.9 (moderate), and greater than or equal to 30 (severe). Results. The median level of urine protein/creatinine ratio in all categori es of OSA was <0.2 (range 0.03 to 0.69: median 0.06 in patients with normal apnea hypopnea index. 0.06, 0.07, 0.07 in patients with mild, moderate. an d severe OSA. respectively). Eight subjects had a urine protein/creatinine ratio greater than 0.2. Univariate analysis showed a significant associatio n between urine protein/creatinine ratio and older age (P < 0.0001). hypert ension (P < 0.0001), coronary artery disease (P = 0.003). and arousal index (P = 0.003). Body mass index (P = 0.16). estimated creatinine clearance (P = 0.17) and apnea hypopnea index (P = 0.13) were not associated with the u rine protein/creatinine ratio. In multiple regression analysis. only age an d hypertension were independent positive predictors of the urine protein/cr eatinine ratio (P < 0.0001, R-2 = 0.17). Conclusion. Clinically significant proteinuria is uncommon in sleep apnea. Nephrotic range proteinuria should not be ascribed to sleep apnea and deser ves a thorough renal evaluation.