Search

Background: Previous studies have reported an association between obstructive sleep apnea (OSA) and proteinuria, but are limited in their ability to assess proteinuria accurately, to adjust for confounders such as obesity, or to exclude confidently underlying renal disease in patients with OSA and nephrotic-range proteinuria., Methods: The spot urine protein/creatinine ratio was measured in a prospective consecutive series of 148 patients referred for polysomnography who were not diabetic and had not been treated previously for OSA. The urine protein/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 > or =30 (severe)., Results: The median level of urine protein/creatinine ratio in all categories 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, and severe OSA, respectively). Eight subjects had a urine protein/creatinine ratio greater than 0.2. Univariate analysis showed a significant association between urine protein/creatinine ratio and older age (P < 0.0001), hypertension (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 urine protein/creatinine ratio. In multiple regression analysis, only age and hypertension were independent positive predictors of the urine protein/creatinine ratio (P < 0.0001, R2 = 0.17)., Conclusion: Clinically significant proteinuria is uncommon in sleep apnea. Nephrotic range proteinuria should not be ascribed to sleep apnea and deserves a thorough renal evaluation.

Background: Proteinuria severe enough to be in the nephrotic range has been noted on occasion in patients with obstructive sleep apnea (OSA), but it is not known what factors are related to the severity of proteinuria in these patients. This study was conducted to determine if the severity of proteinuria is related to the number of apneas., Methods: The level of proteinuria was determined by the dipstick method in 407 patients in whom OSA had been diagnosed. The apnea-hypopnea index (AHI) was calculated in each patient after all-night polysomnography. Sleep apnea was defined as the presence of at least 30 apneas during a 6- to 8-hour monitoring period and an AHI greater than 15., Results: The apnea-hypopnea index in patients without proteinuria was similar to that of patients with 1+ to 3+ proteinuria. However, the AHI was significantly greater in the 9 patients with 4+ proteinuria., Conclusions: While severe proteinuria in OSA occurs in patients with a higher rate of sleep apneas, the lesser degree of proteinuria cannot be explained by AHI alone. Other factors that determine the severity of the disease, such as hypoxemia, merit further investigation.

Two patients with severe obstructive sleep apnea syndrome and high-grade proteinuria (greater than 1 g/d [1000 mg/d]) were studied. Three remissions in proteinuria coincided with correction of obstructive sleep apnea syndrome and improvement of blood oxygen levels. These remissions could be dissociated from reductions both in dry body weight and in hematocrit levels. We propose that sleep apnea may cause a functional and reversible type of proteinuria.

We observed nocturnal urinary protein excretion to be 16.2 +/- 5.5 micrograms/min (mean +/- SE) in 9 healthy control subjects (group I), 29.3 +/- 9.5 micrograms/min in 12 obese patients suspected to have obstructive sleep apnea syndrome (OSAS) but with negative polysomnographic studies (group II), and 94.0 +/- 31.8 micrograms/min in 14 patients with documented OSAS (group III) (II vs. I, NS; III vs. I, p less than 0.05; III vs. II, p less than 0.05). The frequency of abnormal proteinuria, defined as protein excretion greater than the highest rate observed in group I (46 micrograms/min), was 14% in group II and 64% in group III (p less than 0.05). There were no significant differences in age, body weight, body surface area, blood pressure, or indices of sleep apnea between OSAS patients with and without proteinuria. Although the mechanism is unclear, this study shows that nocturnal protein excretion rates are commonly elevated in patients with OSAS.