We agree with Dr Mirrakhimov that age, obesity, and comorbidities such as congestive heart failure and cerebrovascular disease are recognized risk factors for the development of obstructive sleep apnea. In addition, chronic medical disorders, such as COPD, may cause nocturnal hypoxia. In view of this, we surveyed patients for these risk factors and found that those with chronic kidney disease (CKD) and end-stage renal disease (ESRD) generally were older and heavier and had a higher prevalence of these comorbidities.1 Consequently, we performed a multivariate analysis to determine how much these risk factors and kidney function status contributed to the increased prevalence of sleep apnea and nocturnal hypoxia. We found that although age, BMI, and neck circumference were associated with sleep apnea, kidney function status, reflected by ESRD, was also associated with the presence of sleep apnea independently of other traditional risk factors for obstructive sleep apnea. Furthermore, we found that CKD was associated with the presence of nocturnal hypoxia independently of COPD. Notwithstanding the limitations of our cross-sectional design or residual confounding due to unmeasured factors, these findings suggest that chronic kidney failure contributes significantly to the pathogenesis of sleep apnea and nocturnal hypoxia in this patient population.