Statistical analysis
The patients who died, or did not complete the follow-up period, were
excluded from the study as the analysis of the changes in frailty status
after surgery was not possible.
Continuous variables are expressed as median and interquartile interval
(IQI) or mean and standard deviation (SD), depending on the normality of
their distribution as assessed with Shapiro-Wilk normality test.
Categorical data are presented as counts and percentages.
Differences among the three ordinal levels of frailty were analyzed
considering the presence of a linear trend between categories. The
Mantel Haenszel linear trend test was used for categorical variables,
and linear regression models were employed for quantitative ones.
Concordance between frailty scales was assessed with the Kappa index.
Chi-square test was used to compare the distribution of frailty groups
before and after surgery. Changes in the proportion of patients who
score a point in each of the components of the frailty phenotype was
analyzed using the Mc Nemar’s test for paired proportions.
All the statistical analysis and graphics were performed using Stata/IC
15.0 Software (Statacorp LP, College Station, TX). A significance level
p<0.05 was considered as statistically significative.