Supplementary Material for: Association between Obstructive Sleep Apnea and Acute Kidney Injury in Critically Ill Patients: A Propensity-Matched Study

Background/Aims: Obstructive sleep apnea (OSA) is a known risk factor for chronic kidney disease (CKD); however, its association with acute kidney injury (AKI) is not well documented. We aimed to study whether OSA is associated with the risk of AKI in the intensive care unit (ICU) setting. Methods: All consecutive adult Olmsted County, MN residents who were admitted in Mayo Clinic ICUs from January 1, 2010 to December 31, 2010 were screened. Chronic and acute risk factors were collected within the first 48 h of ICU admission. Logistic regression and propensity score matching were used to examine crude and adjusted associations of OSA with AKI. Results: Among 1,259 enrolled ICU patients, 183 patients had a diagnosis of OSA prior to the index ICU admission. Compared with non-OSA patients, the incidence of AKI in OSA patients was more frequent (41 vs. 57%, p < 0.001). In univariate analysis, it was found that CKD, age, gender, Caucasian race, congestive heart failure, cerebrovascular disease, diabetes mellitus, body mass index, and OSA were associated with AKI. In the multivariate model, following adjustment for age, gender, race, and chronic and acute risk factors, OSA was found to have an independent association with AKI (OR 1.53; 95% CI 1.04-2.24; p = 0.031). Among 176 propensity score matched pairs, there was a significant difference in the incidence of AKI between the OSA and non-OSA groups (OR 1.54; 95% CI 1.01-2.35; p = 0.04). Conclusions: The history of OSA diagnosed by polysomnography is associated with higher risk of AKI in critically ill patients.