Declining Kidney Function Increases the Prevalence of Sleep Apnea and Nocturnal Hypoxia

Background: Sleep apnea is an important comorbidity in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). Although the increased prevalence of sleep apnea in patients with ESRD is well established, few studies have investigated the prevalence of sleep apnea in patients with nondialysis-dependent kidney disease, and no single study, to our knowledge, has examined the full spectrum of kidney function. We sought to determine the prevalence of sleep apnea and associated nocturnal hypoxia in patients with CKD and ESRD. We hypothesized that the prevalence of sleep apnea would increase progressively as kidney function declines.

Methods: Two hundred fifty-four patients were recruited from outpatient nephrology clinics and hemodialysis units. All patients completed an overnight cardiopulmonary monitoring test to determine the prevalence of sleep apnea (respiratory disturbance index ≥ 15) and nocturnal hypoxia (oxygen saturation < 90% for ≥ 12% of monitoring). Patients were stratified into three groups based on estimated glomerular filtration rate (eGFR) as follows: eGFR ≥ 60 mL/min/1.73 m(2) (n = 55), CKD (eGFR < 60 mL/min/1.73 m(2) not on dialysis, n = 124), and ESRD (on hemodialysis, n = 75).

Results: The prevalence of sleep apnea increased as eGFR declined (eGFR ≥ 60 mL/min/1.73 m(2), 27%; CKD, 41%; ESRD, 57%; P = .002). The prevalence of nocturnal hypoxia was higher in patients with CKD and ESRD (eGFR ≥ 60 mL/min/1.73 m(2), 16%; CKD, 47%; ESRD, 48%; P < .001).

Conclusions: Sleep apnea is common in patients with CKD and increases as kidney function declines. Almost 50% of patients with CKD and ESRD experience nocturnal hypoxia, which may contribute to loss of kidney function and increased cardiovascular risk.