Statistical analysis
factorTo, POCD
REGRESSION, MINOR
The scaling of volumetric data was adjusted from cubic millimeters to cubic centimeters. Statistical significance was defined as p < 0.05. Multicollinearity was assessed with the variance inflating factor (VIF) per variable. Multicollinearity was assumed at VIF > 2.5. Baseline missing-data were considered to be missing at random. The sample size for this specific analysis was not predetermined. However, general sample size calculations were undertaken for neuroimaging biomarkers in BioCog (see For the analysis of preCI and POCD, we ran a logistic regression model for each outcome. The accuracy of logistic regression models was determined using the area under the curve (AUC) of a receiver operating characteristic (ROC) curve. An AUC above 0.7 indicated a sufficient predictive value.In this study, we intended to elucidate the role of the thalamus volume. Hence, thalamus volume was set as the predictor variable. We report unadjusted and adjusted odds ratio (OR). Adjustment covariates were integrated into the logistic regression based on their dependence structure prior to the statistical analysis. Since preCI was determined analogically to the definition of POCD, we used the same covariates for the preCI regression. For POCD, higher age was presented as a risk factorTo account for potential effects from the surgical procedure, we undertook a post-hoc sensitivity analysis, where we further included the surgery severity (minor, moderate, major and major+), type and duration of surgery. Moreover, we performed another sensitivity analysis using composite z-scores of cognitive data. The z-scores were calculated for baseline and follow-up data based on 928 surgical patients enrolled in the BioCog study. We also analyzed the change in z-scores from pre- to postoperative. Three linear regression models contained the thalamus as variable of interest and the respective z-scores as dependent variable. We again adjusted for age, sex and intracranial volume.We used Graphpad Prism (Version 9.3.1 GraphPad Software, Inc.) for the statistical analysis and for creating graphs.