Limitations
POCD, postoperative delirium
DISEASE, COMPLICATIONS, POSTOPERATIVE COMPLICATIONS
This study faces further limitations. The patients more susceptible to developing POCD due to experiencing severe postoperative complications or suffering from a significant disease were, for these same reasons, more likely not to attend the 3 month follow-up. This may lead to an inherent selection bias within the follow-up cohort. Therefore, we probably underestimate the true number of patients with POCD. Patients who experienced major complications after surgery such as postoperative delirium are underrepresented in our POCD evaluation. For instance, only one patient with POCD (4%) had also experienced POD in the early days after surgery. This does not appear plausible considering the POD incidence of 44 (14.6%) for the whole analysis sample. The loss to follow-up was also higher than expected. The sample size was not predefined. We cannot rule out that this may not have caused insufficient statistical power. We recommend a detailed analysis with further independent surgical cohorts.The relatively low POCD incidence might also be a direct consequence of a relatively strict cut-off of 1.96 in the reliable change index model defining relevant cognitive change. Applying an RCI method could also have caused other issues in the studyThe anesthesiologic management was not standardized. However, to avoid the effect of deep anesthesia and high burst suppression rates all study participants were monitored with an intraoperative electroencephalogram (Masimo Sedline) according to the routine clinical treatment standard. We were not able to account for potential confounders that arose from the anesthesiologic handling.Volumetric analyses can be affected by a variety of external and transient factors such as diurnal fluctuations, medication and hydration status