2.4. Statistical Analysis

Continuous data were analysed with the Shapiro-Wilk test to determine their distribution, and skewed variables were logarithmically transformed before analysis. The cut-offs for PNS were computed as the VPT ≥ 97.5th percentile from age- and gender-adjusted regression models in the nondiabetic controls. From the regression models, VPT > 24 V in males and >21 V in females were used to define PNS. Variables with normal distribution were presented as mean ± standard deviation and analysed using Student's t-test or analysis of variance, as deemed appropriate. Variables with nonnormal distribution were presented as median and interquartile range and analysed using Mann–Whitney U test or Kruskal-Wallis test, as deemed appropriate. Categorical data were analysed by the χ² test. Zero-order and partial Pearson's correlation tests were used to test the association between VPT versus arterial stiffness indices and patient characteristics. Multivariable linear and logistic regression models were performed to analyse the association between VPT/PSN and indices of arterial stiffness.