The pattern of overnight changes in novel markers of acute kidney injury in patients with obstructive sleep apnea.

BACKGROUND

Obstructive sleep apnea (OSA) may predispose patients to acute kidney injury (AKI) and chronic kidney disease (CKD).

OBJECTIVES

We postulated that apneic episodes during sleep in patients with OSA may result in episodes of subclinical AKI that may be detected by the use of novel sensitive serum and urine markers. The treatment of OSA may protect against renal injury.

MATERIAL AND

METHODS

The study involved 86 men who had positive screening test results for OSA and estimated glomerular filtration rates (eGFR) calculated with the Chronic Kidney Disease Epidemiology Collaboration (CDK-EPI) equation >60 mL/min/1.73 m². All the patients underwent overnight polysomnography (the diagnostic night). The patients were divided into 2 groups: 45 patients with mild OSA and 41 patients with moderate-to-severe OSA. Those in the latter group were qualified for 6-8 weeks of continuous positive airway pressure (CPAP) treatment. Blood pressure, serum creatinine, high sensitivity C-reactive protein (hsCRP), urine creatinine, AKI markers cystatin C and neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule 1 (KIM-1), liver-type fatty acid-binding protein, and endothelium marker intercellular adhesion molecule-1 (ICAM-1) were assessed in both groups before and after polysomnography. The same parameters were also measured in the patients with moderate-to-severe OSA after CPAP therapy.

RESULTS

Kidney injury molecule 1 and urine NGAL significantly increased after the diagnostic night in the whole group and in mild OSA patients (p = 0.04 and p = 0.001, respectively). Serum ICAM-1 significantly decreased after the diagnostic night only in mild OSA patients (p = 0.03. Urine cystatin C increased after 6-8 weeks of CPAP treatment in the moderate-to-severe OSA group (0.003). Serum ICAM-1 decreased after the CPAP treatment (p = 0.02). The CPAP therapy led also to a decrease in mean and diastolic (p = 0.005) blood pressure.

CONCLUSIONS

The pattern of overnight changes in serum and urine AKI markers after apneic episodes during sleep may suggest an increased risk of subclinical AKI in patients with OSA. The CPAP therapy is not protective against AKI, but may reduce some of its risk factors, including high blood pressure and endothelial damage.