Statistical analysis
SPSS v. 22 (IBM SPSS Statistics, IBM Corporation, Chicago, IL, USA) was
used for data analysis. Descriptive analysis for continuous variables
was performed. Categorical variables were displayed as absolute numbers
and percentages. Median survival age was the primary
outcome,19 assessed by the Kaplan-Meier analysis;
groups were compared with the log-rank test. Duration of survival was
defined as the time between the date of birth and date of death, or the
last follow-up. Median age at death was calculated for all individuals
in the cohort. Influence of risk factors was assessed by a uni- and
multivariate Cox regression model, with 95% confidence intervals (CI).
A P value < 0.05 was considered significant.