2.2. Data Analysis
The distribution of the variables was assessed through graphical representation. Continuous variables are displayed as mean and standard deviation or as median and interquartile range according to their distribution. Categorical variables are described as N and percentage of the total. Weight, height, and BMI z-scores were estimated using World Health Organization (WHO) references [The Student’s We also assessed the association between feeding type and blood pressure at 11 years of age. We considered different models, adjusting for potential confounders such as country, sex, maternal smoking during pregnancy, birth weight, and anthropometrical parameters, as well as kidney size at 6 months and at 11 years of age. To better understand the effect of early nutrition on blood pressure at 11 years, we performed mediation analysis considering kidney size at 6 months as a possible mediator.Statistical significance was accepted at the level of All statistical analyses were conducted with RStudio 2021.09.0+351 “Ghost Orchid” Release (077589bcad3467ae79f318afe8641a1899a51606, 20 September 2021) for Windows. For mediation analysis, we used the R package “mediation”.The trial was approved by the ethics committees in each study center and written informed consent was obtained from parents or caregivers. All research was performed following the Declaration of Helsinki.