Incidence of postoperative delirium in patients with preoperative and postoperative Obstructive Sleep Apnea Syndrome. A Systematic Review of the literature.

Introduction: Clinical research has suggested that there might be a correlation between postoperative delirium (POD) and obstructive sleep apnea (OSA) syndrome. We aimed to assess the association between POD and OSA syndrome. Methods: The electronic database PubMed was searched using combinations of terms for "Delirium,'' "Obstructive Sleep Apnea,'' and "postoperative delirium.'' Excluded were studies without comparison as well as cross-sectional studies, case series, and case reports. The search was conducted with restriction toward English or not to the date of publication. Results: We included four studies in this review. In two of those studies, an association was found between POD and OSA syndrome. Pooled analysis showed a significant correlation between the two. Conclusion: High-quality studies regarding the subject are rare and heterogeneous. However, despite the lack of high-quality studies regarding the subject, the ones that are performed well conclude that there is a correlation between POD and OSA syndrome. Future studies addressing the matter should be well set up controlled clinical trials to draw conclusions and be able to investigate modifiable factors that can be used in a standardized protocol.