CPAP appears to protect kidney function of patients with OSA

Background: Previous studies demonstrated a direct causal effect of chronic kidney disease on both obstructive and central sleep apnoea. On the other hand, kidneys are sensitive to hypoxia and they might be affected by intermittent desaturation caused by sleep apnoea. Here we test the hypothesis that continuous positive airways pressure therapy (CPAP), which prevents these episodes of desaturation, could have a protective role in the kidney function of patients with obstructive sleep apnoea (OSA). Methods: Renal function measurements (U&E) of patients with OSA, who were initiated on CPAP were retrospectively collected. We excluded U&E performed during acute admissions. We extracted at least 3 U&E within 2 years before the initiation of CPAP and 3 U&E afterwards. Using creatinine measurements prior to CPAP initiation, we predicted the values for the remaining measurements (mean values if kidney function was stable overtime or linear regression to predict future results in cases where creatinine had a clear increasing trend overtime [>10%/year]). Paired t-test was used to assess the difference between the expected and actual values. Results: Using data from 49 patients and 173 U&E after CPAP initiation, we found that our predicted values were significantly higher compared to actual creatinine levels of these patients (p Conclusion: Our results suggest CPAP might have a protective effect in the kidney function of patients with OSA.