Sample size calculation and subgrouping according to age
The number of healthy controls who were enrolled in the parent study was 100. All 100 controls were included as study participants in the current study. Using the power command in Stata, we conducted a one-sample correlation test to estimate the minimum sample required to detect a correlation of a least r=0.3 between RALS and age. The minimum sample size required was 100. All participants were subdivided into three age groups (Group 1:18−29 years, Group 2: 30−39 years, Group 3: 40-49 years and Group 4: 50-70 years).