Do patients with obstructive sleep apnea have clinically significant proteinuria?

Aim: Previous studies report a high prevalence of proteinuria in patients w ith obstructive sleep apnea syndrome (OSAS). This common syndrome may there fore be an important cause of proteinuria and renal failure in the general population. This study was undertaken to assess the prevalence of proteinur ia among OSAS patients, and to identify the factors associated with urine p rotein excretion in these patients. Methods: Overnight polysomnography, uri ne protein to creatinine ratio (PTCR), body mass index (BMI), mean arterial pressure (MAP), and hematocrit were assessed prospectively in 224 patients referred for evaluation of suspected OSAS. Sleep apnea was defined as apne a-hypopnea score (AHS) greater than or equal to 5 events/hour. Proteinuria was defined as PTCR > 0.2 mg/mg. Results: Sleep apnea was present in 143 su bjects (63.8%), and proteinuria in 10 (4.5%). The highest PTCR was 0.677 mg /mg. PTCR and AHS were weakly correlated (r = 0.12, p = 0.08). PTCR correla ted (a = 0.05) with lowest oxygen saturation (r = -0.18, p = < 0.01), time spent with oxygen saturation below 90% (r = 0.19, p = < 0.01), and BMI (r = 0.17, p = < 0.01). The mean PTCR was similar in subjects with and without sleep apnea. Proteinuria was present in 7 of 143 (4.9%) subjects with AHS g reater than or equal to 5 and 3 of 81 (3.7%) subjects with AES < 5, a relat ive risk of 1.34, 95% CI (0.34, 5.32). Predictors of LogPTCR in multiple li near regression (model R-2 = 0.104) were: AHS (< 5 or ! 5), baseline oxygen saturation, sex, and MAP. Conclusions: Clinically significant proteinuria is uncommon in OSAS. The prevalence and severity of proteinuria are similar in both OSAS patients and patients without sleep-disordered breathing. Sle ep apnea severity is weakly associated with urine protein excretion, relate d more to hypoxemia than to frequency of apneic events.