Sleep-disordered breathing and urinary albumin excretion in older men

Purpose: Sleep-disordered breathing(SDB) may be deleterious to the cardiovascular system and other organs, including the kidney. Although older men are at increased risk for both kidney disease and SDB, it is unknown whether SDB is associated with higher urinary albumin excretion in this population. Methods: We examined 507 community-dwelling men age≥67 years(mean 76.0±5.3) enrolled in the MrOS Sleep study who underwent overnight polysomnography and gave a spot urine sample. SDB severity was categorized using the respiratory disturbance index and percent total sleep time <90% oxygen saturation (%time O2<90). Urinary albumin excretion was expressed using the albumin-to-creatinine ratio(ACR). Results: There was a graded association between respiratory disturbance index and ACR (age- and race-adjusted mean ACR=9.35 mg/gCr for respiratory disturbance index≥30 versus 6.72 mg/gCr for respiratory disturbance index<5, p=0.007). This association was attenuated after further adjustment for body mass index (BMI), hypertension and diabetes and no longer reached significance (p=0.129). However, even after adjustment for age, race, BMI, hypertension, and diabetes, greater %time O2<90 was associated with higher ACR (10.35 mg/gCr for ≥10%time O2<90 versus 7.45 mg/gCr for <1%time O2<90, p=0.046). Conclusion: SDB, measured by elevated respiratory disturbance index or nocturnal hypoxemia, was associated with higher ACR. The relationship between respiratory disturbance index and ACR was partially explained by higher BMI and greater prevalence of hypertension and diabetes among men with SDB. However, greater nocturnal hypoxemia was independently associated with higher ACR, suggesting that the hypoxia component of SDB may mediate any detrimental effect of SDB on the kidney.