Statistical Analysis
Continuous data are presented as mean (± standard deviation) for
normally distributed variables or median [interquartile range (IQR)]
for non-normally distributed variables. Categorical data are displayed
as number (percentage). Kaplan Meier analysis was used to evaluate
five-year survival and cumulative incidence of all-cause readmission.
Cox proportional hazards modeling was used to model postoperative
mortality. In this model, all baseline characteristics and risk factors
were assessed in a univariable model. Those with significant
associations with mortality (P<0.05) were considered for
inclusion in the final multivariable model. Backwards, stepwise
elimination was performed to create the final model with covariable
inclusion of P<0.2 into the final model. Significant
covariable interactions and multicollinearity were investigated.
Competing risk regression was used to model all-cause hospital
readmission. In this model, death was the competing event. Baseline
characteristics and risk factors were assessed in a univariable model,
and those with significant associations (P<0.05) with
all-cause readmissions were included in the final multivariable model.
Statistical analyses were performed using SAS version 9.2 software (SAS
Institute, Cary, NC).