Descriptive statistics
Continuous variables were described using the mean and standard deviation, or median and interquartile range when variables were not normally distributed. The independent t-test was used to compare means of continuous variables by sex while the Mann-Whitney test for comparison of median values by sex. One way analysis of variance (ANOVA) was used to compare means of normally distributed continuous variables by age group or BMI category, while Kruskal Wallis was used for comparison of medians when variables were not normally distributed. Pearson’s correlation coefficients determined the association between age and RA parameters using a statistical significance threshold of 0.05. All statistical analyses were conducted in Stata version 15.